Future Climate Analysis Rev 00, ICN 00

ANL-NBS-GS-000008

March 2000

1. PURPOSE 
This Analysis/Model Report (AMR) documents an analysis that was performed to estimate 
climatic variables for the next 10,000 years by forecasting the timing and nature of climate 
change at Yucca Mountain (YM), Nevada (Figure 1), the site of a potential repository for highlevel 
radioactive waste. The future-climate estimates are based on an analysis of past-climate 
data from analog meteorological stations, and this AMR provides the rationale for the selection 
of these analog stations. The stations selected provide an upper and a lower climate bound for 
each future climate, and the data from those sites will provide input to the infiltration model 
(USGS 2000) and for the total system performance assessment for the Site Recommendation 
(TSPA-SR) at YM. 
Forecasting long-term future climates, especially for the next 10,000 years, is highly speculative 
and rarely attempted. A very limited literature exists concerning the subject, largely from the 
British radioactive waste disposal effort. The discussion presented here is one method, among 
many, of establishing upper and lower bounds for future climate estimates. The method used 
here involves selecting a particular past climate from many past climates, as an analog for future 
climate. Other studies might develop a different rationale or select other past climates resulting 
in a different future climate analog. 
This AMR was prepared in accordance with the Work Direction and Planning Document for 
Future Climate Analysis (Z. Peterman 1999) under Interagency Agreement DE-AI08- 
97NV12033 with the U.S. Department of Energy (DOE).

The activities documented in this AMR were evaluated in accordance with QAP-2-0, Conduct of 
Activities, and were determined to be subject to the requirements of the DOE Office of Civilian 
Radioactive Waste Management (OCRWM) Quality Assurance Requirements and Description 
(QARD) (U.S. Department of Energy 1998). This evaluation is documented in Wemheuer 1999 
(Activity Evaluation for Work Package WP 8191213UU1 UZ PMR Rev 0 for SRCR Analysis & 
Writing). This AMR has been prepared in accordance with procedure AP-3.10Q, R2 Analyses 
and Models.

3. COMPUTER SOFTWARE AND ANALYSIS USAGE 
No software or models were used in performing this analysis.

4. INPUTS 
This document may be affected by technical product input information that requires 
confirmation. Any changes to the document that may occur as a result of completing the 
confirmation activities will be reflected in subsequent revisions. The status of the input 
information quality may be confirmed by review of the Document Input Reference System 
database. 
4.1 DATA AND PARAMETERS 
Data sets used in this analysis are summarized in Table 1. 
Table 1. Summary of Data Sets Used as Data Inputs 
Data Inputs Data Tracking Number 
Diatom Data from Owens Lake 1984-1992 Cores. GS970708315121.001. 
Ostracode Data from Owens Lake 1984-1992 Cores. GS970708315121.002. 
Supplementary Data to Ostracode Data From Owens lake 1984  1992 cores. GS991008315121.001. 
Supplementary Data to Diatom Data From Owens Lake 1984-1992 cores GS991008315121.002. 
Earthinfo, Inc. Western U.S. Meteorologic Station weather Data  NCDC 
Summary of Day (West 1) and NCDC Summary of Day (West 2). 
GS000100001221.001. 
Earth Orbital Parameter Data for the Present to 100,000 year in the Future. GS000200005121.002. 
Earth Orbital Parameter Data for the Last 10 Million Years. GS000200005121.001. 
Radiometric Dating and d18O Data from Devils Hole, Nevada. GS000200005121.003. 
These data sets were used because this analysis provides a rationale for a specific set of climates 
and, from that, a basis for other analyses and models using this information to evaluate 
uncertainty within the confines of these climate characteristics in order to determine if this 
degree of climate change is adverse to the site. The parameters of past climate were used for a 
select set of representative meteorological stations to estimate values for future climates. These 
parameters are appropriate because they are the input parameters needed for the analysis of 
infiltration at the site. Specifically, the appropriateness of the data inputs listed in Table 1 
dealing with the diatom, ostracode, and depth to age relationship data are discussed in Section 
6.5. The appropriateness of data inputs covering radiometric dating from Devils Hole, Nevada is 
discussed in Section 6.3; for data inputs summarizing the day observations from the National 
Climatic Data Center the appropriateness is discussed in Section 6.6; and for the earth orbital 
parameter data, it is discussed in Section 6.4. 
4.2 CRITERIA 
Formal criteria have not been established for the development of this AMR; however, this 
analysis complies with the DOE interim guidance (Dyer 1999). Subparts of the interim guidance 
that apply to this analysis or modeling activity are those pertaining to the characterization of the 
Yucca Mountain site (Subpart B, Section 15), the compilation of information regarding 
hydrology of the site in support of the License Application (Subpart B, Section 21(c)(1)(ii)), and 
the definition of hydrologic parameters and conceptual models used in performance assessment 
(Subpart E, Section 114(a)).

 
 
4.3 CODES AND STANDARDS 
No specific formally established codes or standards have been identified as applying to this 
analysis.

5. ASSUMPTIONS 
Four key assumptions are fundamental to the future climate analysis. The basis for each of the 
assumptions is discussed in the subsections of Section 6, except for assumption 4, which is 
assumed for the time frame in question: 
1. Climate is cyclical, so past climates provide insight into potential future climates; in other 
words, the past is the key to the future (Section 6.3). 
2. A relation exists between the timing of long-term past climate change (the glacial/interglacial 
cycles) and the timing of changes in certain earth-orbital parameters. This establishes a 
millennial-scale climate-change clock, which provides a possible way to time future climate 
change (Section 6.4). 
3. A relation exists between the characteristics of past climates and the sequence of those 
climates in the long, approximately 400,000-year, earth-orbital cycle. The characteristics of 
past glacial and interglacial climates within the long earth-orbital cycle differ from each 
other, and appear to do so in a systematic way. This climate sequence relation provides a 
defensible criterion for the selection of a particular past climate as an analog for future 
climate (Section 6.5). 
4. Long-term earth-based climate forcing functions, primarily tectonics, that operate on the 
million-year time scale have remained relatively unchanged during the last long earth climate 
cycle, and will not change during the next 10,000 years. Consequently, the potential and 
unpredictable impact of long-term, earth-based forcing functions on climate need not be 
considered for understanding climate change during the past 400,000 years or the next 
10,000 years. 
The first three assumptions cannot be confirmed by testing, analysis, or design because of the 
inherent nature of estimating or predicting future climate states. The second assumption builds 
on the first, and the third builds on the second. Only the passage of 10,000 years will tell if the 
assumption that a particular past climate is a viable analog for the future climate. 
The assumption (number 4) that long-term, earth-based forcing functions will not change during 
the next 10,000 years, and therefore, impacts on climate need not be considered for 
understanding climate change during the next 10,00 years is consistent with EPA proposed rule 
40 CFR 197 (EPA). In speaking of the 10,00 year compliance period, the EPA states, (2) There 
are likely to be no exceptionally large geologic changes during that time, (Federal Register, 
Vol. 64, No. 166/Friday, August 27, 1999/Proposed Rules, page 46994). 
Further verification of these assumptions is not warranted.

 
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6. ANALYSIS 
6.1 INTRODUCTION 
Past climate was analyzed to select representative meteorological stations that can be used to 
estimate climate values for future climates, such as mean annual and seasonal precipitation, and 
mean annual and seasonal air temperature, at Yucca Mountain, Nevada for the next 10,000 years. 
These climate values then provide the input terms for the infiltration model (USGS 2000) at YM. 
The analysis depends on the assumptions of climate cyclicity, of the accuracy of an earth-orbital 
parameter climate-change clock, of the repetition of particular past climate states in the future, 
and of relative tectonic stability during the past long earth-orbital cycle and for the next 10,000 
years. The basis for each of the first three assumptions is discussed below along with the general 
nature of modern-day climate, which serves as a reference for comparison with past climates. 
The constancy of tectonic scale climate change will be assumed for the 10,000-year time frame, 
but can not be assumed for million-year time scales past or future. 
The causes of climate change in the past between glacial and interglacial conditions are not 
known, but this analysis attempts to establish timing relations between earth-orbital parameters 
that can be calculated and climatecycle relations that can be recognized from the past and used 
to forecast the future. Any future climate analysis is uncertain, but perceived relations between 
measurable cycles enable an attempt to forecast estimated future climate conditions. 
A map of the Western United States (U.S.) showing the locations of specific sites discussed in 
this AMR is provided in Figure 1.

 
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Figure 1 Western United States Showing Localities Discussed in the Text

 
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6.2 MODERN AND PAST CLIMATE 
A generalized schematic of modern day atmospheric circulation (climate) is shown in Figure 2. 
For the purposes of this analysis, the modern-day earth climate system may be thought of as a 
three-component system, consisting of two active components, the tropical (Hadley) and polar 
cell air masses, and of a more passive mixing zone between them, the westerlies (Ferrel cell). 
The northern edge of the tropical air masses, the Subtropical Highs, consist of highpressure, 
descending air that creates a hot, dry and, hence, low precipitation and high evaporation climate. 
The Subtropical Highs define the global hot desert belts and dominate the climate of the YM 
region today. Regions south of the Subtropical Highs fall under the influence of the much wetter 
subtropical easterlies.

 
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Figure 2. Generalized View of Atmospheric Circulation 
Source: modified from Ahrens (1985, fig. 15.7) 
NOTE: Time approximates Autumnal Equinox; H = high pressure dominates; L = low pressure dominates; arrows show dominant direction of air 
movement.

 
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The southern edge of the polar air masses, the Polar Lows, consist of low-pressure, rising air that 
creates a cool, wet and, hence, high precipitation and low evaporation climate. The average 
seasonal position of the Polar Lows approximately defines the Boreal Forests and also dominated 
some past glacial climates in the YM region. The central (northernmost) part of the polar air 
mass is characterized, especially in winter, by dense, cold, descending air creating lower 
tropospheric high-pressure cells. Air streams flow southward from these high-pressure cells 
producing the Arctic (Polar) easterlies. Arctic (Polar) Highs are typically characterized by cold, 
dry air, and hence low-precipitation and low-evaporation climates. The Arctic Highs also 
dominated some past glacial climates in the YM region. 
The mixing zone between the tropical and polar air masses, the westerlies, have a complex 
weather system consisting of high- and low-pressure air masses or cells that often produce 
storms along the air-mass boundaries. These high- and low-pressure cells may be short lived 
(hours or days) or may persist for a week or more. The precipitation and temperature 
characteristics within the westerlies are typically seasonal, and related to the proximity of the 
tropical or the polar air masses. The southern edge of the Polar Lows, along the boundary with 
the westerlies, is commonly called the polar front and is the area where the polar jet stream 
resides. The polar jet stream acts as a steering current for westerly storms. Similarly, the 
northern edge of the Subtropical Highs may be referred to as the subtropical front and is the 
location of the subtropical jet stream. 
Regional climate in the conterminous U.S. is a result of the seasonal expansion and contraction 
of the tropical and polar air masses. In southerly areas of the U.S. tropical air masses and warm 
westerlies dominate the annual climate, whereas in northerly areas climate is dominated by polar 
air masses. 
The general climate characteristics associated with the global air masses are often modified by 
regional features such as topography, large lakes, and the oceans. The Sierra Nevada Mountains 
and the Transverse Range have exerted significant control over past YM climate, continuing to 
the present day. Fundamentally, these mountain ranges cut the YM region off from its major 
moisture source, the Pacific Ocean, and especially from the subtropical Pacific Ocean. By 
creating and sustaining a major rain shadow in the YM region, the mountain ranges also have 
amplified the evaporative action of the Subtropical Highs during modern-day and past 
interglacial climates. 
Today in the YM region, from late spring through early fall, climate is dominated by the 
northward movement and intensification of the Subtropical Highs. Present-day subtropical high 
activity, in the YM region, does not, however, intensify to the point of creating a strong 
monsoonal weather pattern, as happens in southern Arizona and New Mexico and in Mexico. 
Rather, the subtropical high activity commonly produces convective thunderstorms, typically of 
only local importance, and intense evaporation, which is enhanced by the mountains to the west 
and southwest. 
During late fall through early spring, the Subtropical Highs weaken and retreat south, leaving the 
region largely under the influence of the westerlies, whose moisture potential is greatly reduced 
by the Sierra Nevada Mountains, and to a lesser extent by the Transverse Range. Polar Low and

 
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occasionally Arctic High pressure may intrude into the area, resulting in wetter and less 
evaporative conditions. The wettest winters are often associated with the El Nino years, when 
the polar front moves south over the Pacific Ocean, steering subtropical moisture into the YM 
region. El Nino years are also high infiltration years (Winograd et al. 1998), but the El Nino 
circulation is usually not sustained, and the Subtropical Highs return to exert their evaporative 
influence over the regions hydrology. This Subtropical-High-dominated climate regime has 
dominated regional climate for about the past 9,000 to 10,000 years, with some episodes being 
hotter and drier, and others being cooler and wetter, than modern (see, for example, Forester et 
al. 1999, Figure 14). 
The modern interglacial climate, and that of the past 8,000 years or so, is not typical of climate 
during the last several hundred thousand years. Past climates have included glacial periods, and 
a variety of climates intermediate between glacial and interglacial, all of which may be 
simplistically thought of in terms of dominance of the polar and tropical air masses. The 
expansion of continental ice into the U.S. means that the polar air masses expanded and became 
persistent in more southerly areas throughout the year, otherwise the continental ice and snow 
would have melted. Because the basic physical laws of atmospheric circulation are conserved, 
when the polar air masses expand and become more persistent, the Polar Lows must also move 
southward, both in the sense of the seasonal extreme and their average position. As the Polar 
Lows expand southward, the wet, cool boreal realm moves southward, resulting in wetter and 
cooler conditions in places that today are warmer and drier. Local topography and air-mass 
dynamics will modify the polar low climate, such that, for example, the very wet northwest U.S. 
climates do not get literally transposed southward. 
In the YM region a glacial climate would mean longer winter seasons and shorter summer 
seasons. Subtropical Highs would be less persistent, so mean annual temperature (MAT), 
summer temperature, and the high summer evaporation would be lower, resulting in the potential 
for more infiltration, even if mean annual precipitation (MAP) remained constant. MAP, 
however, wont remain constant, because there would be more frequent and persistent incursions 
of polar-low activity, bringing more rain and snow during glacial periods than today. Infiltration 
is further increased during these periods, because winter precipitation, as melting snow, would be 
less likely to evaporate or be used by the vegetation, so evapotranspiration (ET) would be much 
lower. During some glacial periods, when large continental ice sheets existed, Arctic Highs were 
likely resident in the YM region for much or perhaps all of the year, resulting in very cold and 
dry conditions, with limited evaporation (Whitney and Harrington 1993; Thompson et al. 1999c). 
Relative to modern climate, infiltration would be higher during these cold, dry climates, because 
evaporation would be lower. 
There were also interglacial periods in the YM region, especially during transitions from or to a 
glacial period, that appear to have been warmer and wetter than the typical interglacial period 
(Forester et al. 1999). During these periods, the Subtropical Highs would have expanded and/or 
intensified, resulting in a northward shift of the southwestern monsoon. Summer precipitation 
probably increased dramatically, resulting in higher MAP, but because this was summer 
precipitation, much of it likely was lost to ET, due to higher air temperatures, and active 
transpiration by the vegetation community. Conversely, there also were times during glacial

 
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transition climates when the climate was wetter than during some glacial periods and cooler than 
the interglacial period (but not extremely cold), potentially enhancing infiltration. 
On time scales of hundreds of thousands of years, climate change is large, and hence change in 
climate parameters affecting infiltration also is large. The largest amounts of infiltration 
probably occurred when very large continental ice sheets existed, resulting in cold, low 
evaporative conditions in the YM region. Although the interglacial (modern-like) climates only 
persisted for about twenty percent of the documented interglacial/glacial history (Forester et al. 
1999; Winograd et al. 1997), the times when very large ice sheets existed also were limited, so 
much of the YM climate history is dominated by intermediate climates. For example, the full icemaximum 
of the last glacial period, around 21,000 years ago, lasted only a couple of thousand 
years. By contrast, the penultimate glacial period from about 140,000 to 175,000 years ago may 
have sustained a large ice sheet for as much as 35,000 years, with cold, low-evaporative, and 
possibly wet conditions in the YM region. The importance of the penultimate glacial in the YM 
region is shown by the existence at that time of a large, 175-m-deep lake in Death Valley (Ku et 
al. 1998), now one of the driest areas in the U.S. Other glacial climates, for example those about 
300,000 to 400,000 years ago, were cool and wet, rather than cold and either dry or wet, in the 
YM region. Each glacial and interglacial period appears to have a characteristic climate with 
unique infiltration characteristics. The nature of all climate change can be simplified as a 
seasonal interplay of the polar, tropical, and westerly air masses. 
6.3 THE CYCLICAL NATURE OF CLIMATE CHANGEDEVILS HOLE 
The first assumption for this analysis is that climate is cyclical, and thus the past can be used to 
forecast the future. That is, if climate change exhibits some rhythmic pattern, then future 
climates will repeat, or at least approximate, past climates. For this particular assumption, that is 
that climate is cyclical, the only issue is whether or not the present-day interglacial period will be 
followed by a climate change toward glacial and then eventually into a glacial climate. Past 
climate cycles are a series of glacial/interglacial couplets. To illustrate the cyclic nature of past 
climate, the delta oxygen-18 (d18O) isotope record from a calcite core at Devils Hole, Nevada, 
about 90 kilometers (km) south of YM (Figure 1), provides the best information about climate 
change in the region (Landwehr et al. 1997). Stable isotope compositions are typically reported 
in delta (d) notation as the per mil deviation of the ratio of the heavy to light isotopes (18O/16O) 
in the sample to that of a reporting standard (VSMOW, Vienna Standard Mean Ocean Water, for 
18O/16O). 
Devils Hole is an active extensional fracture in the Paleozoic limestone that composes the 
regional Paleozoic aquifer. During the last 500,000 or more years calcite has precipitated on the 
walls of the fracture, leaving an isotopic record of the regional ground water flowing through the 
fracture (Winograd et al. 1992). The calcite has been cored, and the core has been extensively 
dated (Ludwig et al. 1992). The d18O data (Landwehr et al. 1997, DTN: GS000200005121.003) 
from one core show an irregular cyclicity between high and low values for the last 425,000 years 
(Figure 3).

 
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Figure 3. Devils Hole Stable Isotope Record Showing the Timing and Cyclical Nature of Climate Change 
Sources: Devils Hole d18O and radiometric data from DTN: GS000200005121.003, Marine Isotope Stage data from Imbrie and Imbrie (1986) 
NOTE: Stable isotope data are reported relative to VSMOW. High Devils Hole d18O values represent warm climates and low values represent cold climates. Odd 
numbered Marine Isotope Stages (MIS) correspond to interglacial climates, even numbered MIS correspond to glacial climates.

 
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The d18O isotopic composition of ground water flowing through the Devils Hole fracture (Figure 
3) (Landwehr et al. 1997) records the isotopic composition of infiltration in the recharge area of 
the regional aquifer (Winograd et al. 1992). The isotopic values of infiltration are related to 
three factors: 1) The isotopic composition and temperature of the source water, the tropical and 
subtropical Pacific Ocean; 2) The path that the water vapor takes from the source to the recharge 
area, and the amount of precipitation that occurs along the path; and 3) The temperature at which 
the precipitation in the recharge area forms. 
When water evaporates from a source water the degree of fractionation (under equilibrium 
conditions) depends on the temperature of the source: the colder the source, the greater the 
fractionation (Kim and O'Neil 1997). The resulting vapor has a d 18O value that is equal to the 
source minus the fractionation factor, so the vapor has a lower value than the source water. 
Equilibrium conditions often do not exist in the source areas, resulting in vapor values that are 
even lower than those that result from equilibrium conditions (Grootes 1993). Some of the 
ocean-derived vapor moves over the continent forming precipitation as snow or rain and over 
time that precipitation returns to the ocean, completing the hydrological cycle. During glacial 
periods, however, a significant amount of the precipitation is stored as snow and ice, and thus 
does not return to the ocean. Consequently, the isotope value of the ocean becomes higher 
during glacial periods. The cycle in d18O values in marine carbonates between low and high 
values records the storage or loss of continental ice, and hence glacial or interglacial climates. 
There may be a corresponding change in the isotope values of precipitation in the Devils Hole 
recharge area, reflecting changes in the isotope values of the source areas. But, a source area 
signature, because it would be small relative to the path effects, is not evident in the Devils Hole 
d 18O record (Landwehr et al. 1997, DTN: GS000200005121.003). 
The path and conditions along the path taken by vapor as it moves from the source area toward 
the recharge area have an important effect on the d18O values of precipitation in the recharge 
area. As vapor is chilled, whether from rising through the atmosphere due to thermal expansion 
or over topography or due to mixing with cooler air, some vapor turns to rain or snow. The 
fractionation as vapor turns to precipitation reverses that of evaporation, so precipitation has a 
higher d18O value than its vapor source. Following each precipitation event, the remaining vapor 
has an ever-lower value. If the path to the recharge area involves extensive precipitation, then 
the precipitation in the recharge area will have low d18O values, and if the vapor path does not 
involve extensive precipitation, then the precipitation in the recharge area will have relatively 
high values. Typically, interglacial precipitation has higher d18O values than glacial precipitation 
because the glacial path involves more precipitation, so in the carbonate d18O record from Devils 
Hole (Landwehr et al. 1997, DTN: GS000200005121.003), high values represent interglacial 
climates, and low values represent glacial or glacial-transition values (the opposite of the ocean). 
Finally, because fractionation between vapor and precipitation is temperature dependent, the 
d 18O values of precipitation from very cold snow should be higher than those of warm snow and 
those of warm snow should be higher than those of rain. Thus, if all other factors along the 
vapor path were constant, a very cold glacial period would have higher d18O infiltration values, 
which are close to precipitation values, than a warm glacial period. Because all other factors are 
not constant, recognition of temperature differences for precipitation in the recharge area 
between different glacial climates is not probable.

 
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The cycles in the d18O data from Devils Hole for the past 425,000 years (Landwehr et al. 1997, 
DTN: GS000200005121.003) reflect a cyclic change from interglacial to glacial climates, each 
of which can be identified by a number (Figure 3) for a marine isotope stage (MIS), where odd 
numbers are interglacials and even numbers are glacials. The MISs are derived from the marine 
carbonate d18O records that reflect changes in d18O values of ocean water as continental ice 
sheets expand and contract (see discussion in CRWMS M&O 1998, p. 4.2-9 to 4.2-12; 
Shackleton and Opdyke 1973). The MIS and Devils Hole chronologies are not correlated 
exactly, and, in particular, differ in the timing of the glacial terminations (Winograd et al. 1992). 
The Devils Hole chronology is assumed to be most appropriate for the Yucca Mountain region 
and is used in this report. 
The Devils Hole d18O record (Landwehr et al. 1997, DTN: GS000200005121.003), as interpreted 
in terms of changes in isotopic values of infiltration in the recharge area, shows that climate is 
cyclic on a millennial time scale. The cycles, however, differ in duration (see also Winograd et 
al. 1992; Ludwig et al. 1992; Winograd et al. 1997). 
6.4 TIMING OF PAST-CLIMATE CHANGE AND EARTH-ORBITAL PARAMETERS 
The second key assumption in this analysis is that the timing of past climate change provides a 
rationale for timing future climate change. Timing future climate change requires that such 
change be based on parameters whose future values can be accurately calculated. Earth-orbital 
parameters, whose past and future values are readily calculated from basic celestial mechanics, 
provide the necessary values, if and only if a relation exists between the timing of climate change 
and those parameters. Using identifiable relations between orbital parameters and the timing of 
past climate change to forecast future climate change is within NRC acceptance criteria (U.S. 
Nuclear Regulatory Commission 1997). Because the causes of past change from interglacial to 
glacial and back to interglacial climates remain unknown, using the timing of past climate 
change as a basis for the future timing of climate change should be viewed with caution. 
Recognition of relations between climate change and orbital parameters demands a welldated, 
long, earth-based climate record, a record with a very accurate internal chronology. A good 
earth-based climate chronology allows for confident comparison of the timing of change between 
the climate and the orbital parameters. The timing of orbital parameters is derived from basic 
celestial mechanics, and is discussed by Berger and Loutre (1991), whose values are used in this 
discussion (Figures 4 and 5). The time under consideration is the past 400,000 years, because 
that interval of time is about equivalent to the long earth-orbital cycle, also known as a long 
eccentricity cycle. The long eccentricity cycles are not exactly 400,000 years in duration (Figure 
5). For example, the time between the high value of eccentricity just before 400,000 years ago 
and the high value before 0 years is about 391,000 years. The exact time between the 
corresponding eccentricity values of earlier cycles is not constant, but for simplicity of 
discussion all will be referred to herein as 400,000-year cycles. Imbrie et al. (1992) and Imbrie, 
Berger et al. (1993), among many authors, provide a discussion of the perceived relation between 
orbital dynamics and climate change (SPECMAP, see discussion in CRWMS M&O 1998, p. 4.2- 
10). Winograd et al. (1992) have challenged the linkage between orbital forcing of climate 
change based on the difference between timing of climate change in the Devils Hole record

 
31  
(Landwehr et al. 1997, DTN: GS000200005121.003) and the SPECMAP chronology (see 
discussion in CRWMS M&O 1998, p. 4.2-14). However, that is not at issue here, because the 
Devils Hole chronology of climate change is used in this analysis.

 
32  
Source: modified from Imbrie and Imbrie (1986, figs. 13, 14, 16) 
Figure 4 Generalized View of Precession, an Orbital Parameter related to the Timing of Earth's Long- 
Term Climate Change

 
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There are three orbital parameters, each having its own periodicity: 1) eccentricity, the shape of 
the earths orbit changing in a systematic way from an ellipse to circular and back to an ellipse 
with time, about every 100,000 years; 2) obliquity, the angle of the Earths axis of rotation 
changing a few degrees with time, about every 41,000 years; and 3) precession, the wobble of 
the Earths axis like that of a spinning top changing with time, about every 23,000 years. 
Precession, which dominates insolation (heat from the sun as measured at the top of the 
atmosphere) at low latitudes, is the primary parameter used here to identify the timing of climate 
change (Figures 4 and 5). Because of precession the summer of perihelion (the point in the orbit 
nearest the sun) shifts from one hemisphere to the other about every 11,500 years or so. Figure 5 
shows how eccentricity amplifies or dampens the precession value. Obliquity, which influences 
the nature of seasonality at high latitudes and is a key component in SPECMAP, did not show 
any consistent relation with the Devils Hole record (Landwehr et al. 1997, DTN: 
GS000200005121.003), so it is not considered further.

 
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Figure 5. Relation Between Precession and Eccentricity for the Past 425,000 Years 
DTN: GS000200005121.001

 
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The orbital cycles (Berger and Loutre 1991, DTN: GS000200005121.001) are compared with the 
Devils Hole climate change chronology (Landwehr et al. 1997, DTN: GS000200005121.003) 
because Devils Hole is the only accurately and independently dated climate record on earth. 
Other long, dated climate records exist, but typically the chronology for those records relies on 
extensive interpolation between dates. So, in this analysis, the Devils Hole record forms the 
basis for the comparison and timing of climate change. The temporal changes in the orbital 
parameters are compared with the Devils Hole climate change chronology in search of an orbital 
clock that agrees with the times for climate change at Devils Hole and from that can be used to 
time future climate change. The latter is the opposite of common practice in which climate 
records acquire their chronology from orbital data, and that is because all earth records except 
Devils Hole lack a continuous internal chronology. 
A general qualitative relation between Devils Hole data (Landwehr et al. 1997, DTN: 
GS000200005121.003) and precession (Berger and Loutre 1991, DTN: GS000200005121.001) 
is evident where maximal values of precession mark the ends of the Devils Hole interglacials and 
other warm periods (Figure 6). That qualitative relation was expanded into a formal relation 
between the Devils Hole d18O profile, precession, and eccentricity from direct inspection of the 
respective curves. The formal relation provides an orbital clock that offers a rationale for timing 
future climate change in terms of the Devils Hole chronology of climate change in the YM 
region. Imbrie, Mix, and Martinson (1993) and Shaffer et al. (1996) also have identified 
similarities between the Devils Hole d18O profile and orbital parameters. In the latter two studies 
Devils Hole data were compared to orbital parameters (the opposite of what was done in this 
study) to determine if the Devils Hole record reflects orbital forcing, that is, is the variation in 
the Devils Hole d18O profile attributable to variation in orbital parameters, and if so, is the 
variation in the Devils Hole d18O profile evidence for the assumption that changes in orbital 
parameters cause climate change?

 
36  
DTN: GS000200005121.003, GS000200005121.001 
Figure 6. Relation of Precession to the Devils Hole Stable Isotope Climate Proxy Record During a Long Climate Cycle 
NOTE: Stable isotope data are reported relative to VSMOW.

 
37  
The existence of an orbital clock, defined below, that times change in the Devils Hole record 
(Landwehr et al. 1997, DTN: GS000200005121.003) may not indicate climate change is caused 
by change in orbital parameters. Change in orbital parameters may simply be correlated with 
some other factor that causes climate change, such as solar output (Gauthier 1999), or may be a 
relatively minor factor, but one that tips the balance and drives the earth's climate system over 
some unknown threshold (Shaffer et al. 1996). Although the relation with timing of past climate 
change with changes in the earth-orbital parameters provides information about the timing of 
climate change, it does not imply magnitude or nature of climate change. 
In order to describe the formal relation for orbital timing of climate change, the relation between 
Devils Hole d18O (Landwehr et al. 1997, DTN: GS000200005121.003) and precession (Berger 
and Loutre 1991, DTN: GS000200005121.001) shown in Figure 6 was examined. Notice that 
the inflection points in the Devils Hole data marking a change from a high towards a low value 
coming forward in time correspond to high precession values. Precession plays the dominant 
role in determining the nature of tropical and subtropical insolation, so a relation between the 
precession spectra and the Devils Hole record may imply a linkage between climate change and 
tropical insolation. 
By comparing the Devils Hole d18O and age data (Landwehr et al. 1997, DTN: 
GS000200005121.003) with orbital parameter and age data (Berger and Loutre 1991, DTN: 
GS000200005121.001), a formal relation was found to determine which precession values are 
the ones that define the beginning or the end of a glacial period, so the relation could be applied 
in a consistent way to the orbital-parameter data in the future. The relation, starting with the end 
of the interglacial period around 400,000 years ago, appears to consistently identify all of the 
primary inflection points in the available Devils Hole record (new work at Devils Hole has 
extended the record from about 50,000 to about 9,000 years ago, but those data are not yet 
available). 
Inspection of precession plots (Figures 7a and 7b) and of the timing of precession versus Devils 
Hole d18O (Figure 6) shows that, in particular, a maximal positive precession (letter I in Figures 
7a, 7b, and 8) marks the approximate termination for all of the interglacials defined by the Devils 
Hole record. By convention, a maximal positive precession is maximum precession (see Figures 
4 and 5) in the Southern Hemisphere, whereas a minimal (most) negative value is maximum 
precession in the Northern Hemisphere.

 
38  
Source: orbital data from DTN: GS000200005121.001 
Figure 7a. Proposed Relation Between the Timing of Past Climate Change and Earth-Orbital Parameters 
During a Long Climate Cycle; Continuation of Diagram is Given as Figure 7b 
NOTE: I = initiation of transition to glacial climate; T = initiation of transition to interglacial climate; m = minimum eccentricity value.

 
39  
Source: orbital data from DTN: GS000200005121.001 
NOTE: I = initiation of transition to glacial climate; T = initiation of transition to interglacial climate; m = minimum eccentricity value. 
Figure 7b. Continued from Figure 7a; Proposed Relation Between the Timing of Past Climate Change and 
Earth-Orbital Parameters During a Long Climate Cycle

 
40  
Termination of interglacials is here defined as the point in time where the Devils Hole d18O 
curve (Landwehr et al. 1997, DTN: GS000200005121.003) moves from high interglacial values 
towards lower values, that is, the terminal inflection point in an interglacial sequence coming 
forward in time, identified by the number below the letter I in Figure 8. It is less evident, but 
will be suggested below, that minimal precession values mark the ends of glacial periods, which 
are here defined as the point in time where the Devils Hole d18O record reverses its trend from 
low values and moves progressively towards high values, that is, the primary inflection point in 
the curve beyond which the values become progressively higher, identified by the number near 
the letter T in Figure 8. Selecting inflection points at the ends of interglacials and glacial periods 
to mark the beginnings and ends of (inter)glacial periods is not conventional, but better suits the 
purposes of this study.

 
41  
Source: Devils Hole data from DTN: GS000200005121.003 
NOTE: Stable isotope data are reported relative to VSMOW; I = initiation of transition to glacial climate; T = initiation of transition to interglacial climate; Ages for I 
and T are shown in parentheses at bottom of graph; Ages for inflection points are shown in box. 
Figure 8. Relation of Data Shown in Figures 7a and 7b and the Timing of Climate Change Defined by the Devils Hole Climate 
Proxy Record

 
42  
Final glacial inflection points (see Figure 8), that is the Devils Hole inflection point marking the 
point after which the Devils Hole d18O values become progressively higher (Landwehr et al. 
1997, DTN: GS000200005121.003), are defined by the first minimal (Northern Hemisphere 
precession maximal) precession value (letter T in Figures 7a and 7b) (Berger and Loutre 1991, 
DTN: GS000200005121.001) following an eccentricity minimum value (letter m in Figures 7a 
and 7b). If a precession minimum coincides with an eccentricity minimum, which happens with 
the first glacial period in the 400,000-year cycle, then the next precession minimum marks the 
final glacial inflection point. The next (younger) interglacial inflection point, that is the 
inflection point in the Devils Hole record after which the d18O values become progressively 
lower, occurs at the first precession maximal value about 30,000 years after the preceding 
precessional minimum (Figures 7a and 7b). The 30,000-year value is a constant that was found 
by inspection to work for the entire 400,000-year sequence and has no other special significance. 
The general nature of (inter)glacial climate probably does not change at the primary inflection 
points, but rather change towards an (inter)glacial climate begins at that point. And, climate does 
not necessarily move continuously towards an (inter)glacial. The Devils Hole d18O profile 
(Landwehr et al. 1997, DTN: GS000200005121.003) is a relatively smooth curve indicating a 
continuous transition toward and into (inter)glacial climates, but the Devils Hole data points 
integrate about 1,000 years or so (Winograd et al. 1992). Examination of a higher resolution 
curve such as the deuterium record of the last 420,000 years from Antarctica (Petit et al. 1999) 
shows a pattern of numerous small magnitude climate reversals that occur on decade and century 
time scales. In fact, the Devils Hole d18O record shows a reversal at about 220,000 years ago 
that is seemingly small in magnitude and only persists for a couple of thousand years. So these 
primary inflection points in the Devils Hole record identified with the precession methodology 
should not be thought of as absolute timings of climate change because climate reversals towards 
(inter)glacials may well occur following the inflection point. 
The timing of (inter)glacial bounding precession maximal and minimal values (Berger and 
Loutre 1991, DTN: GS000200005121.001) are shown on the Devils Hole d18O curve (Figure 8) 
(Landwehr et al. 1997, DTN: GS000200005121.003). The correspondence between the 
precession-based and Devils Hole-based sets of values is nearly identical in most cases and off 
by 10,700 years in one case. Although the primary inflection points signal the beginning of 
change to the next climate state, there is a substantial amount of time following each primary 
inflection point until the next climate state is reached. For example, an interglacial climate, as 
defined by the Devils Hole d18O values reaching a plateau following a glacial period, takes from 
about 20,000 to 25,000 years after the glacial primary inflection point. 
The differences between the timing of the precession-based ages (Berger and Loutre 1991, DTN: 
GS000200005121.001) and the ages of the Devils Hole d18O inflection points (Landwehr et al. 
1997, DTN: GS000200005121.003) could be caused by several factors. The differences may 
reflect the age uncertainty in the Devils Hole dates, even though that uncertainty is usually small. 
The difference could be due to the methodology of selecting a precession value that marks the 
Devils Hole d18O inflection points, if precession values represent a fortuitous correlation with 
climate change. Or the differences could be a function of regional climate, where a Devils Hole 
primary inflection point precedes or follows global change.

 
43  
The largest discrepancy between the Devils Hole d18O record (Landwehr et al. 1997, DTN: 
GS000200005121.003) and precession (Berger and Loutre 1991, DTN: GS000200005121.001) 
occurs at the end of interglacial stage 5e, which at Devils Hole is 126,700 years ago (Figure 8). 
The penultimate interglacial, stage 5e, was warmer than the present interglacial, as sea level was 
higher than today (Muhs and Szabo 1994). The d18O values from the Devils Hole record for this 
interglacial period are higher than for the other interglacials. As noted above, high d18O values 
for precipitation in the recharge area imply limited rain out along the path taken by vapor from 
the source to the recharge area. Thus the primary inflection point at the end of the interglacial 
stage 5e in the Devils Hole d18O data may reflect a change in the vapor path, but not the actual 
end of that interglacial period. Szabo et al. (1994) place the end of interglacial stage 5e at about 
114,000 years ago. The precessional timing for the end of this stage is 116,000 years ago (Figure 
8) and thus at a similar relative age difference as observed for earlier interglacial primary 
inflection points. If the Szabo et al. (1994) timing is used, all of the precession ages and the 
available Devils Hole inflection point ages are within 2,500 years or less of each other, a good 
agreement for the two sets of data. 
The value of the proposed orbital clock for forecasting the timing of future climate change 
(Figures 7a, 7b, and 8) can be viewed from another perspective. If it were 400,000 years in the 
past, at the beginning of the last orbital cycle rather than the present, would the forecast for the 
future, as shown in Figure 8, be viewed as an accurate forecast for the timing of climate 
change? Given the enormous uncertainties about how the climate system works, and about the 
nature of past or future climate, it appears that this forecast would be a good forecast. However, 
there is an aspect in this forecast that needs to be addressed and its cause or implication is 
unknown. 
The precessional method (Berger and Loutre 1991, DTN: GS000200005121.001) for identifying 
the primary inflection points within the Devils Hole record (Landwehr et al. 1997, DTN: 
GS000200005121.003) indicates there is a primary glacial inflection point at about 33,000 years 
ago, thus indicating climate change toward warmer conditions. Because the younger part of the 
Devils Hole record is not available, it is not known if the minimal precession value at 33,000 
years ago corresponds with an inflection point in the Devils Hole record. If the Devils Hole 
record responds in the same manner about 33,000 years ago as it has in earlier parts of the 
record, then it should show an inflection point within a couple of thousand years of 33,000 years 
ago. 
Winograd et al. (1996) discuss the younger part of the Devils Hole record and describe a sharp 
warming trend beginning at about 28,000 years ago as well as other evidence for warmth in this 
time frame. The earlier T events in Figure 8 have higher d18O values about 5,000 years later 
(33,000 minus 28,000 years) and because higher d18O values imply greater warmth, warmth at 
Devils Hole at 28,000 years ago is consistent with the older parts of the record. Thompson et al. 
(1997) also present evidence for warmth in the late 30,000-year time frame and other evidence 
for warmth at this time is common in the literature. Thus as with other periods marked with a T 
in Figure 8, the one at 33,000 years ago appears to precede a warming period, but unlike the 
other T periods, not a continuous warming period.

 
44  
Following the warm period from about 32,000 through about 25,000 years ago, there was an 
extensive growth and advance of a continental glacier from about 24,000 to 18,000 years ago, 
with ice maximum around 21,000 years ago (Thompson et al. 1997). The climate characteristics 
in the vicinity of Yucca Mountain reflect a glacial climate (Thompson et al. 1999c, Forester et al. 
1999). In terms of the precession methodology (Berger and Loutre 1991, DTN: 
GS000200005121.001) and its relation to the Devils Hole d18O record (Landwehr et al. 1997, 
DTN: GS000200005121.003) this represents a significant reversal in the pattern displayed in the 
transition periods from full-glacial climates toward the interglacial climates observed in all 
earlier transitions in the past 400,000-year cycle. And presumably this glaciation and its 
portrayal in the Devils Hole d18O record are much greater than the reversal at about 220,000 
years ago. By contrast the present interglacial, the Holocene, begins about 10,000 years ago, 
23,000 years after the 33,000-years-ago precession maximum in the Northern Hemisphere. The 
latter timing is consistent with timing for the beginning of earlier interglacials following the 
primary glacial inflection point. Thus, the last glaciation maximum about 21,000 years ago, 
which is not predicted by the precession methodology, may simply be an example of a climate 
variation, a feature that is typical of the last glacial cycle in the long orbital cycle, or an 
inconsistency in the precession orbital clock methodology. 
The precession methodology is applied to the next 100,000 years in Figure 9 (DTN: 
GS000200005121.002). The timing of possible climate change toward and away from a glacial 
period is the same as for the change beginning about 400,000 years ago (Figures 7a, 7b, and 8). 
The duration between the initiation of climate change (I) at 399,000 years ago toward a glacial, 
and then away (T) from the glacial is 44,000 years (Berger and Loutre 1991, DTN: 
GS000200005121.001). In Figure 9, the timing from a move towards the glacial period (I at 
1,000 years ago) to the move away (T at 44,000 years ago) is 45,000 years. As shown in Figure 
8, the timing for the move towards and away is much longer for the remaining three glacial 
periods in the 400,000-year cycle, with durations of 58,000 years, 80,500 years, and 83,000 
years.

 
45  
Source: orbital data from DTN: GS000200005121.002 
NOTE: I = initiation of transition to glacial climate; T = initiation of transition to interglacial climate; m = minimum eccentricity value. 
Figure 9. Proposed Timing of Future Climate Change During the Next 100,000 Years

 
46  
The discussion above indicates that a precession-based orbital clock, calibrated with the Devils 
Hole chronology, provides a basis to time climate change from the interglacials toward glacials 
and from glacials towards interglacial climates. This clock times the beginnings and ends of the 
major climate events during the last 400,000-year cycle and provides a potential clock for such 
events in the future. 
Climate change, however, does not move steadily from interglacials to glacials and back again, 
but instead climate change is a complex array of intermediate climates between interglacial and 
glacial extremes. The intermediate climates may be truly intermediate in nature or they may be 
warmer and wetter or drier than the interglacials and colder and wetter or drier than the glacials. 
Understanding the timing of intermediate climates could be important, if they were to occur in 
the next 10,000 years. So the question becomes do changes in precession provide insight into 
climate change on shorter intervals of time. 
To investigate identifying and forecasting climate change for shorter intervals of time than is 
discussed above, Figure 10 shows the relation between precession (Berger and Loutre 1991, 
DTN: GS000200005121.001) and the Devils Hole record (Landwehr et al. 1997, DTN: 
GS000200005121.003) from 425,000 to 350,000 years ago. The rationale for the selection of 
this interval will be discussed in more detail below, where it will be suggested that the interval 
from about 399,000 years to 389,000 years ago in the Devils Hole chronology is the analog for 
future climate. The minor lows and highs in the Devils Hole d18O data approximately, but not 
perfectly, correspond to the rises and falls in the precession values. This pattern is maintained 
for the entire Devils Hole record (Figure 6). Specifically, the change in precession from a 
maximal value to 399,000 years ago (maximum precession in the Southern Hemisphere) to a 
minimum value at about 390,000 years ago (maximum precession in the Northern Hemisphere) 
coincides with a change from a high d18O value (end of the interglacial) to a lower d18O value, 
presumably indicating a change toward a wetter and or cooler climate (Figure 10). The Devils 
Hole d18O record continues to rise and fall in approximate synchroneity with precession, 
eventually moving to a low value at 355,000 years ago reflecting the full glacial climate. The 
intriguing and puzzling aspect about the correspondence between precession and the Devils Hole 
d18O record is that in some cases there is a tendency for low values of d18O to correspond with 
minimal precession values, which represent insolation maxima in the Northern Hemisphere 
summer, and so correspond with processes that, from the isotope data, indicate cooler and or 
wetter conditions in the recharge area. Perhaps this implies there is no causal relation between 
precession and the Devils Hole d18O record or perhaps it means the response of the climate 
system follows or leads precession. Or perhaps it means maximal precession in the Northern 
Hemisphere, and consequently maximum summer insolation in the Northern Hemisphere, are 
linked somehow to the genesis of moisture necessary for the initiation of a glacial period, and if 
so that would seem to indicate that tropical climate drives climate change. Whether or not these 
or other factors are involved, these data indicate the timing of the minor inflection points in the 
Devils Hole record are at least approximately correlated with precession. Consequently, the 
timing of future subcycles in precession should also approximately time climate change.

 
47  
Figure 10. Relation Between Precession and the Timing of Climate Change in Part of the Devils Hole Record 
from 425,000 to 350,000 Years Ago 
NOTE: Stable isotope data are reported relative to VSMOW. 
DTN: GS000200005121.003, GS000200005121.001

 
48  
Inspection of the precession curve in Figure 9 (DTN: GS000200005121.002) shows that it is 
similar to the precession curve in Figure 10 (Berger and Loutre 1991, DTN: 
GS000200005121.001). Presuming the future precession curve times climate change and marks 
the multitude of intermediate climates that exist between interglacial and glacial climates, then 
such intermediate climates will characterize southern Nevada climate for approximately the next 
30,000 years. Then around 30,000 years from now climate will move into the full glacial climate 
and will have moved out of the full glacial by about 50,000 years from now. 
6.5 THE NATURE OF PAST AND FUTURE CLIMATE 
The third assumption in this analysis is that a general relation exists between the nature of 
climate characteristics of past glacial and interglacial climates and the sequence of those climates 
in the long 400,000-year earth-orbital cycle. This is the most difficult assumption to deal with, 
because support for it depends on the interpretation of paleoenvironments from the penultimate 
400,000-year cycle and data from that cycle are limited. If the temperature and precipitation 
characteristics of past glacial and interglacial climate couplets differ from each other in a 
systematic way through a particular 400,000-year cycle, but the sequence of climate couplets in 
adjacent 400,000-year cycles are similar, then this relation provides a criterion for the selection 
of particular past climates as an analog for future climates in the next 10,000 years or perhaps 
longer at YM. If this assumption is not accepted, then the future climate bounding estimates 
would depend on a conservative estimate of climate or in other words on the extreme 
temperature (very cold) and precipitation (very wet) values from the previous 400,000-year cycle 
instead of values within the extremes. 
Using this relation, the glacial and interglacial climates of the last 400,000-year orbital cycle, 
divided into marine isotope stages (MISs) as shown in Figure 3, will serve as sequential analogs 
for future climates during the next 400,000 years. Although a strict repetition of climate 
characteristics is not expected or implied from the available data, the general characteristics (the 
greatest effective moisture within the next 400,000 years) of future precipitation and temperature 
for a particular interglacial/glacial couplet will be similar to the corresponding MIS couplet in 
the past 400,000-year sequence. Because of tectonic change and other long-term climate forcing 
functions, climate change on the million-year time scale should change in a non-cyclic way, and 
the sequential nature of climate characteristics in non-adjacent 400,000-year orbital cycles may 
be dissimilar from each other. 
6.5.1 Basis for and General Climate History of the Last 400,000 Years 
Comparison of climate series from different 400,000-year cycles requires that climates from the 
last 400,000-year cycle be known in enough detail to serve as a basic reference for comparison 
of climates in older 400,000-year cycles. If the hypothesis of repetition of climates in sequence 
is accepted, the long YM regional climate sequence also provides the future climate analog for 
the next 10,000 years. Although the Devils Hole stable isotope record (Figure 3) (Landwehr et 
al. 1997, DTN: GS000200005121.003) provides the best-dated record for sequence study, it does 
not provide a means of determining the magnitude, that is the nature, of climate events. 
Therefore, another record, the microfossil record from cores drilled at Owens Lake, California, is 
used instead to reconstruct a climate history for the last long orbital cycle.

 
49  
The primary data source for this discussion is the Owens Lake micropaleontological record of 
diatoms and ostracodes (DTN: GS970708315121.001; GS991008315121.002; 
GS970708315121.002; GS991008315121.001), and this discussion will focus on the ostracodes, 
as their story is similar to the diatoms. Diatom data will be used when necessary to support the 
ostracode story. A composite stratigraphic distribution of ostracodes from cores taken in the 
Owens Lake Basin is shown in Figure 11. The relation between the ostracode species 
assemblages and the Owens Lake hydrology and, from that, climate, is discussed in Forester et 
al. (1999) and CRWMS M&O (1998, p. 4.2-16 to 4.2-22), among others, and those discussions 
will only be briefly repeated here.

 
50  
DTN: GS970708315121.002, GS991008315121.001, GS000208315121.002 
Figure 11. Owens Lake Ostracode Species Stratigraphic Distribution 
NOTE: Interglacial marine isotope stages (odd numbers) shown in right column, inferred glacial marine isotope stages (even numbers) shown under L. sappaensis 
column. Bars centered on data spikes indicate data points beyond the scale of the graph, values to right of bars are data values at spike apex.

 
51  
The Owens Lake Basin is located on the eastern side of the Sierra Nevada Mountain Range 
(Figure 1). During the winter season the polar air masses expand (see discussion in Section 6.2), 
resulting in an alignment of the storm track with the Sierra Nevada Mountains. The persistence 
and strength of the storm track is a key factor in determining Sierran snowpack and in turn the 
snowpack determines the amount of runoff available for surface-water flow, that is, flow above 
base flow in the Owens River. 
During an interglacial climate, surface-flow is typically seasonal, but during glacial climates 
surface-flow probably persisted throughout the year or when it did not, evaporation in the Owens 
Basin was greatly reduced from present-day, due to colder air temperatures. The modern-day 
high evaporation in the Owens Basin, estimated to be about 1,500 mm relative to 140 mm 
average local precipitation (Smith 1976), would support a saline Owens Lake, if surface and base 
flow were not diverted to Los Angeles. Thus, under natural conditions present-day annual flow 
is not sufficient to fill and spill Owens Lake. When the Owens River flow was greater and or 
evaporation was lower (low MAT) during glacial and glacial-transition climates, the lake did fill 
and spill, and was filled with freshwater. Primarily because of its location, the Owens Lake 
climate signal is dominated by winter precipitation and summer evaporation. Summer 
precipitation is typically limited, because tropical cyclonic activity does not usually extend into 
the Owens Basin from the southeast. Kay (1982), among others, has documented higher levels 
of summer precipitation associated with tropical storms. There is some indication from the fossil 
record, discussed below, that summer precipitation was an important contributor to Owens Lake 
hydrology in the past. 
A relation between total dissolved solids (TDS) in the lake water, flow in the Owens River, and 
level of evaporation in the Owens Basin exists. Further, flow in the Owens River and level of 
evaporation in the Owens Basin are directly related to climate. When the Polar Lows were 
resident in the region, as during some glacial periods, Sierran snowpack and hence surface-water 
flow was greatly increased, and evaporation in the basin was lower (both actual MAP and 
effective moisture, which is MAP minus evaporation, were high). If Arctic High air were 
resident in the region, then evaporation in the Owens Basin must have been much lower than 
today, due to very cold temperatures, so surface-flow likely was at some intermediate level 
relative to interglacial and the high-MAP, Polar-Low-dominated climates, so effective moisture 
also would have been high and the lake would spill. 
Ostracode and diatom species environmental tolerances provide a way to interpret the relative 
TDS of the Owens paleolake, and the relative temperature of its water. The TDS and watertemperature 
information is then interpreted in climate terms. Thus, the stratigraphic profiles of 
microfossil species provide a way to interpret regional climate history from their implied 
paleoenvironments, and hence insight into glacial and interglacial climate change, and a means 
to compare past climates with each other. Further, North American lacustrine ostracode species 
biogeography is known well enough to use it to understand the general nature of climate change 
in Owens Lake rather than just paleoenvironmental change. Unlike common plant species 
(Thompson et al. 1999a; 1999c) however, the biogeographic distributions of lacustrine 
ostracodes are not mapped, so can not be quantified in climate terms. Thus, particular climate 
parameters are not as readily derived from ostracode assemblage biogeographic data as from

 
52  
plant biogeographic data. Nonetheless, the occurrence of various ostracode species does provide 
a paleogeographic sense (polar, tropical, or temperate) of the nature of past climates. 
Actual climate parameters, however, do not have to be generated from the microfossil species 
profiles to reconstruct long-term climate, as long as the characteristics of, for example, a given 
glacial or interglacial climate can be properly evaluated relative to others. The relative climate 
reconstruction is then compared, that is calibrated, with two absolute climate control points: 1) 
modern meteorological data and 2) the reconstruction of the last glacial climate based on plant 
macrofossils recovered from packrat middens throughout the region (Thompson et al. 1999c). 
Thus the knowledge of ostracode and diatom TDS tolerances, ostracode relative watertemperature 
preferences, and ostracode species biogeography provide a means of directly 
comparing general or relative nature of the past glacial and interglacial climates during the last 
400,000 years. 
A composite stratigraphic distribution of common lacustrine ostracode species from the Owens 
Lake record for about the last 425,000 years is shown in Figure 11 (DTN: 
GS970708315121.002, GS991008315121.001). The chronologies are based on a mass sedimentaccumulation 
model, calibrated by radiocarbon ages at the top of the core, and the Bishop Ash at 
the base of the core (see discussions in Forester et al. 1999, CRWMS M&O 1998, p. 4.2-19 to 
4.2-20). In this basin, as in most basins, sediment accumulation rates are not expected to be 
constant over long periods of time, so a chronology derived from an age model should be viewed 
as an age estimate, at best. Thus in the absence of direct dating, other means must be used to 
date the sediments from the cores. One such means is to identify the interglacial and glacial 
stratigraphic environmental signature from the Owens Lake record and then correlate that 
signature with the Devils Hole record. The Owens Lake chronology shown in Figure 11 is 
provided here for reference only and is not used in the analysis documented in this AMR. 
Forester et al. (1999) and CRWMS M&O (1998, p. 4.2-18 to 4.2-22) discuss the relation 
between diatom and ostracode species, Owens paleolake chemistry, and climate. Briefly, during 
interglacial climates, when, at least on a seasonal basis, Owens River base flow is common, the 
lake becomes both saline and alkaline, that is, its solute chemistry is characterized by a high 
alk/calcium ratio. Alk is total alkalinity expressed as an equivalent amount of calcium carbonate 
(CaCO3). 
Limnocythere sappaensis requires the high alk/Ca water associated with base flow in the Owens 
River to survive (Forester 1983) and such waters characterize the warm climate episodes at 
Owens Lake (Menking et al. 1997). Each abundant L. sappaensis zone is identified with an 
interglacial (warm climate) MIS number starting with 1 and counting backwards in time (Figure 
11) (DTN: GS970708315121.002, GS991008315121.001) (see Winograd et al. 1997, for further 
explanation of MISs). Warm climate episodes also include the warm periods within glacials 
such as MIS substages 5C and 5A. Further, MIS 9, like 7 and 5, has warm and cool substages, 
but the substages are not differentiated here due to loss of core. The L. sappaensis MIS 1 
interval (Figure 11) is only a subset of the true MIS 1, which extends from present-day to about 
10,000 years ago, so the other L. sappaensis intervals also may be subsets of the respective MIS 
stages they are thought to identify. Assuming the Owens Lake sedimentary record (Smith and

 
53  
Bischoff 1997) is reasonably complete, then the L. sappaensis stratigraphic profile identifies all 
sustained warm climates, in other words, those with low effective moisture. 
Comparing the same MIS intervals in the Devils Hole d18O record (Figure 3) (Landwehr et al. 
1997, DTN: GS000200005121.003) and the Owens Lake ostracode record (Figure 11) (DTN: 
GS970708315121.002, GS991008315121.001) indicates that the sediment mass-accumulation 
age model does not provide a good chronology at Owens Lake, because the Owens Lake and 
Devils Hole chronologies do not correlate. So, first the proposed MIS intervals shown in Figure 
11 must be evaluated. If abundant L. sappaensis intervals represent saline lakes when the Owens 
River is at base flow and hence warm, dry climates, then the times between such intervals should 
contain evidence of surface flow, both freshwater and cold conditions; with Owens Lake filling 
and spilling under a polar, cold air mass. That is, if the ostracode profiles shown in Figure 11 
represent the glacial and interglacial climates for the past approximately 400,000 years, then 
there should be an alternating ostracode assemblage reflecting fill and spill cold lakes followed 
by another assemblage reflecting closed saline lakes and so on. 
Cytherissa lacustris and Candona caudata are ostracodes that require low salinity water in order 
to grow and reproduce (CRWMS M&O 1998, p. 4.2-20 to 4.2-21), so their presence in this 
record (DTN: GS970708315121.002, GS991008315121.001) implies a fill and spill lake (Figure 
11). Limnocythere ceriotuberosa is common in lakes receiving seasonal surface flow followed 
by a base-flow phase, so its presence implies greater surface flow than is typical today, but less 
than that during the periods when C. lacustris and C. caudata are common. The stratigraphic 
record in Figure 11 shows that all of the intervals between those identified by L. sappaensis 
variously contain C. lacustris and C. caudata with common occurrences of L. ceriotuberosa. 
Thus the expected sequence of taxa representing fill and spill, freshwater, cold lakes through 
closed, saline lakes is present in the record. This implies the record is complete, and moreover, 
is comparable with the sequence of glacial and interglacial cycles recorded by other records 
reflecting global climate change such as the Devils Hole d18O record. 
The inferences about timing and stratigraphy from the distribution of Limnocythere sappaensis 
and other ostracodes (DTN: GS970708315121.002) are in part supported by a recent revision of 
the Owens Lake chronology (Litwin et al. 1999). Using a high-resolution pollen stratigraphy 
generated in both Searles Lake, California and in Owens Lake, Litwin et al. (1999) correlate an 
alpha spectrometric uranium series chronology from Searles Lake to Owens Lake. They did not 
date the Holocene in Searles Lake, but their pollen stratigraphy for MIS 5A, 5C, and 5E agrees 
with the L. sappaensis chronology proposed here. The ostracodes and pollen data do not 
correlate as well in the older part of the core where the pollen analyses were based on lower 
resolution pollen analysis (Litwin 1999). More recent, but unpublished higher resolution 
analyses have changed the pollen correlation chronology (Litwin 1999), but its effect on the 
ostracode chronology is not yet known, but should be taken into consideration for any future 
revision of the climate AMR. 
Assuming the Owens Lake sedimentary record (Smith and Bischoff 1997) is reasonably 
complete from the discussion above, the ostracode record provides the following insights into the 
regional climate history. The ostracode species stratigraphic profile shown in Figure 11 (DTN: 
GS970708315121.002, GS991008315121.001) shows that Cytherissa lacustris is common for

 
54  
about 2,000 years centered on 20,000 years ago (Owens Lake chronology), which is within MIS 
2 (the last full-glacial period), and again between about 120,000 to 170,000 years ago (Owens 
Lake chronology), which is within MIS 6 (the penultimate glacial period). C. lacustris also 
occurs at a single horizon at about 310,000 years ago (Owens Lake chronology), which is within 
MIS 8. C. lacustris was not found in sediments attributed to MIS 10, even though a large 
number of samples were examined from this interval. Candona caudata is also common through 
the same horizons as C. lacustris and at many horizons within glacial intervals where C. lacustris 
does not occur. 
Cytherissa lacustris is a taxon that lives in small to large lakes in the Boreal Forest and Arctic 
Circle (Delorme 1970), where the climate is dominated by polar air masses. C. lacustris is 
known only from a few large lakes south of Canada and Alaska, such as the Great Lakes. It is 
absent from deep, high mountain lakes in the Sierra Nevada Mountains. The distribution of 
modern-day C. lacustris supports the interpretation that it requires cold and fresh (highest TDS 
occurrence about 300 milligrams per liter, mg/L, Delorme 1989) water to survive. Candona 
caudata lives in Canada and Alaska, but also is common in many locations in the continental 48 
states. The southernmost known distribution for C. caudata is in the Pahranagat Lakes, Nevada, 
and the known upper TDS limit is about 3,000 mg/L (Bradbury et al. 1989). Thus both C. 
lacustris and C. caudata imply fresh fill and spill lakes, and hence wetter than modern climates, 
but the C. lacustris intervals also imply a colder and perhaps fresher lake than the C. caudata 
intervals without C. lacustris. 
The stratigraphic profiles of Cytherissa lacustris and Candona caudata (Figure 11) (DTN: 
GS970708315121.002, GS991008315121.001) indicate that glacial period MIS 10 was the 
warmest glacial period, followed by MIS 8, and MIS 6 was the coldest glacial period. The 
abundance of C. caudata during the warm glacial periods implies MAP was high in order to 
maintain a fresh and spilling lake, although the lake need not be as fresh as it was during the C. 
lacustris intervals, so the C. caudata lakes may imply lower effective moisture levels. 
Significantly, during the coldest glacial, a fresh and spilling lake could be maintained largely by 
low evaporation with only modest gains in MAP above modern levels, so a relatively low MAP, 
but a high effective moisture level. Thus the cold glacials do not require, but do not preclude, 
large increases in MAP to create and sustain a freshwater lake. 
The ostracode Limnocythere ceriotuberosa commonly lives in saline to freshwater lakes in the 
U.S. and on the central Canadian prairies where its habitat is influenced seasonally by polar and 
westerly air masses (Figure 12). It is often found in lakes with seasonal changes in TDS, 
resulting from a seasonal shift from excess surface flow to base flow. In Owens Lake, L. 
ceriotuberosa likely reflects a lake that fills and spills in some years, but is typically at some 
intermediate depth between the C. lacustris and C. caudata continuously spilling lakes, and the 
low-level base-flow-supported saline lakes of Limnocythere sappaensis (DTN: 
GS970708315121.002, GS991008315121.001). Periods when L. ceriotuberosa was common in 
the Owens Lake stratigraphic profile imply intermediate lakes between those produced by fullglacial 
climates and those supported by interglacial climates, and thus indicate intermediate 
climates. Intermediate climates might be somewhat wetter or cooler than modern day or a 
combination of both, but not as wet or cold as the full-glacial climates.

 
55  
Source: modified from Smith and Forester (1994, fig. 1) 
NOTE: One m equals 10-6 meter, "r" indicates right-hand valve, "&" indicates female. 
Figure 12. Modern-Day Biogeographic Distribution of Two Ostracode Species found in the Owens Lake Fossil 
Record Illustrating a Relation Between Biogeography and General Features of Climate (see Figure 2)

 
56  
The past warm, evaporative, low-MAP climates are represented by Limnocythere sappaensis as 
discussed above. The occurrence of this taxon in the Owens Lake record (DTN: 
GS970708315121.002, GS991008315121.001) indicates a saline lake supported largely by base 
flow, and hence a modern-day-like climate or a drier/warmer climate than modern day. It does 
not, however, allow for a climate that is much wetter/cooler than today, because a wetter/cooler 
climate would result in an influx of dilute high-elevation water that is lethal to L. sappaensis. As 
shown in Figure 11, numerous L. sappaensis climates existed in the region during the past 
425,000 years. 
An interesting subclimate associated with the L. sappaensis climates is indicated by the presence 
of Limnocythere bradburyi. Today, the biogeographic distribution of L. bradburyi is centered in 
central Mexico (Forester 1985) where its habitat is influenced seasonally by the subtropical 
easterlies or the subtropical highs (Figure 12). The northern biogeographic limit, in shallowwater 
environments, is the January frost line in the southwestern U.S., indicating it is cold-water 
sensitive (Smith and Forester 1994). Other areas in the southwest that are warm enough are too 
dry to sustain shallow lakes long enough for L. bradburyi to complete its life cycle. However, 
past climates that were warmer and wetter than today, including those where monsoon flow 
through the southwest was enhanced, would sustain shallow, warm lakes promoting a northward 
range expansion of this species. The fossil distribution of this taxon extends into northern 
Nevada (Forester 1985; Forester 1987; Bradbury et al. 1989) and elsewhere and appears to have 
done so during many past warmer and wetter climate episodes. 
Limnocythere bradburyi would not live in Owens Lake during times of higher surface flow, 
when such conditions resulted from resident polar air masses, which would result in a cold lake. 
If L. bradburyi could live in cold water, then its present distribution would be more northerly, as 
it was in the past. The sporadic occurrences of L. bradburyi in the Owens Lake record (Figure 
11) (DTN: GS970708315121.002, GS991008315121.001) are always associated with 
Limnocythere sappaensis lakes, which reflect warmer climates. It does not occur throughout the 
L. sappaensis intervals, because the salinity tolerance of L. sappaensis is higher and its 
temperature tolerance lower than that of L. bradburyi. 
The modern-day northern extent of the southwestern monsoon, showing the area dominated by 
summer precipitation (Muhs 1999), is south of the Owens Basin and YM (Figure 13). However, 
given a modest and uniform expansion of the modern summer rain regime, both YM and the 
Owens Basin would be included. The inclusion of the Owens Basin should change the basin's 
hydrology to reflect a summer, rather than winter precipitation regime, which would be atypical 
for the basin. A dilution of a warm climate saline lake and/or a shift to year round warm waters 
due to an overall expansion of the tropical system and contraction of the polar system, would 
provide an environment like those where Limnocythere bradburyi lives today (Forester 1985; 
Smith and Forester, 1994). The rarity of L. bradburyi in the fossil record (DTN: 
GS970708315121.002, GS991008315121.001) at Owens Lake during the last 425,000 years 
reflects the rarity of tropical regime dominance over winter regimes in the region.

 
57  
Figure 13. Generalized Depiction of the Present-Day Average Distribution of the Southwestern Monsoon 
Source: modified from Muhs (1999)

 
58  
The ostracode species stratigraphic profiles (Figure 11) (DTN: GS970708315121.002, 
GS991008315121.001) provide relative climate scenarios based on inferences about the linkage 
between climate and paleolimnology in the Owens Lake Basin for the past 400,000 years. In 
order to assign approximate values of MAT and MAP to the relative climate scenario, the 
relative scheme must be quantified by comparing it to quantified climate estimates. Two 
climates were selected to calibrate the nature of all of the climates recorded in the Owens Lake 
record from the relative climate scenario: the modern-day climate and the reconstructed climate 
for MIS 2 (Thompson et al. 1999c). Climate parameters for both are estimated for an elevation 
equivalent to the top of YM. 
The modern-day climate is characterized by: 1) Hot, dry, very evaporative summers due to the 
residence of the Subtropical Highs, 2) low levels of MAP due to both the summer air masses and 
to a location east of the Sierra Nevada Mountains, and 3) occasionally wet but typically dry and 
relatively warm winters. Modern-day MAP and MAT as estimated by Thompson et al. (1999c) 
for YM are about 125 mm and 13.5oC respectively. These values are lower than those 
commonly used by the YM project, but are derived from a longer set of historical meteorological 
data and are interpolated to Yucca Mountain from area rather than project stations. The 
Thompson et al. (1999c) numbers are closer to the Nevada region 3 and 4 averages, which 
represent the last 100 years, rather than just the last two decades. The modern-day warm 
interglacial climate at YM is assumed to be typical of all of the Limnocythere sappaensis records 
found in the Owens Lake climate record (DTN: GS970708315121.002, GS991008315121.001). 
By proximity, as climate is a regional and not a local phenomenon, the existence of warm 
evaporative climates at Owens Lake implies that such climates also exist at YM. 
The last full-glacial climate (MIS 2) at YM was characterized by: 1) Cold, wet (snowy) winters 
due to the residence of either Polar Lows or Arctic Highs, creating high effective moisture, and 
2) cool, dry summers resulting from both the presence of cool, westerly flows and the absence of 
Subtropical Highs in the region. The MIS 2 full-glacial climate estimates at YM for MAP is 
about 266 to 321 mm and for MAT is about 7.9o to 8.5o C (Thompson et al. 1999c). These 
estimates are derived from a study of the plant macrofossils found in packrat middens in the YM 
region. 
The values given above provide climate numbers that can be applied to the relative climate 
scheme developed from the microfossil record in the Owens Lake sediments. So, for example, 
MIS 10 was wetter and warmer than MIS 2 and MIS 6. MIS 6 was colder than MIS 2, but 
probably had an MAP similar to MIS 2 to possibly higher than MIS 2. So MIS 10 may have had 
an MAP that was much greater than about 300 mm and an MAT than was higher than about 8 
degrees Celsius (C). MIS 6 by comparison was colder than 8C and had an MAP of about 300 
mm or higher. The Limnocythere ceriotuberosa intermediate climates were typically drier and 
warmer than MIS 2, but wetter and cooler than the modern-day values. So the L. ceriotuberosa 
intervals had an MAP that was greater than 125 mm, but less than about 275 mm and an MAT 
above 8 C but below about 13 C. The Limnocythere bradburyi climates were wetter and 
slightly warmer than the modern-day climates. 
Lastly, the stratigraphic distance between the various ostracode species assemblages in the 
Owens Lake core are small, implying the interpreted climate changes occurred rapidly. Using 
the Owens Lake chronology, the timing of climate change is often occurring in decades to 
centuries and rarely in millennia. Such rapid changes in climate, however, are not generally

 
59  
from the driest and warmest to the wettest and coldest climates, but rather are transitioning 
through many intermediate climate states. 
6.5.2 Repetition of Past Climates 
The assumption discussed in this section is that a general relation exists between the 
characteristics of past glacial and interglacial climates and the sequence of those climates in the 
long 400,000-year orbital cycle. Because the characteristics of past glacial and interglacial 
climates differ from each other and appear to do so in a systematic way, this relation provides a 
criterion for selection of a particular past climate as an analog for future climate. 
The ostracode fossil record from Owens Lake cores (DTN: GS970708315121.002, 
GS991008315121.001) provides the basis to make a number of general observations about 
paleoclimate. Some of these observations for the past 400,000 years include: 
1. The third glacial period in the sequence (MIS 6) was the coldest of the glacial 
climates and had the highest level of effective moisture, but not necessarily the 
highest MAP, 
2. The first glacial period in the sequence (MIS 10) was the warmest, and perhaps the 
wettest of the glacial climates, but probably had a moderate level of effective 
moisture relative to higher effective moisture in the colder glacial periods in the 
sequence, 
3. There were numerous interglacial and related warm climate periods such as MIS 
stages 5A and 5C, when the climate was warm and dry with low effective moisture, 
4. The warm, dry climate periods were occasionally punctuated by warm and wet, but 
low effective moisture, tropical-dominated climates, 
5. There were extensive periods when climate characteristics were intermediate in 
nature between full-glacial high effective moisture and interglacial warm-climate low 
effective moisture periods, and 
6. The rate of change between the various climates was rapid, apparently occurring on a 
decade to century time scale. 
The Owens Lake ostracode hydrologic/climatic record (DTN: GS970708315121.002, 
GS991008315121.001), as partially summarized in 1 through 6 above, indicates that the regional 
climate history for the past 400,000 years was a complex array of climates. Each of the glacial 
climates MIS 10, 8, 6, 4/2 was different from the others and became colder as the sequence 
progressed reaching the coldest and most persistent glacial climate with MIS 6. MIS 6 was 
followed by a complex set of climates ranging from the wet and warm interglacial MIS 5E to the 
cold and relatively short-lived glacial climates, MIS 4 and 2. 
In terms of an orbital clock, today the climate system resides at the beginning of a new 400,000- 
year cycle. If the cycle repeats, then the transition climate at the beginning of the last 400,000- 
year cycle (MIS 11 to MIS 10) may be a more probable analog for future climate than some 
other interglacial to glacial transition. Evidence in support of this idea comes from comparing 
the last cycle (400,000 years ago to present), hereafter referred to as the younger long climate 
cycle (YLCC), to the 400,000-year cycle before the last one, so 800,000 to 400,000 years ago, 
hereafter referred to as the older long climate cycle (OLCC).

 
60  
In comparing the relation between the OLCC and the YLCC, the southwestern regional climate 
records from the OLCC are limited, and existing records are often poorly dated or not interpreted 
in the detail that would be preferable for this study. Further, long-term climate forcing functions, 
primarily tectonic, are probably not constant in this time frame and hence may contribute to 
climates in the OLCC time frame in a different way or with different magnitude than those from 
the YLCC or those in the future. Nonetheless, some information is available from the region, 
including Death Valley, and, more generally from the global marine records. A number of 
studies interpret climate from regional records that are dated or believed to be dated between 
800,000 and 400,000 years ago, for example, see Smith (1984); Jannik et al. (1991); Whitney 
and Harrington (1993); Reheis et al. (1993); Reheis (1999); Knott (1999); and Oviatt et al. 
(1999). A general discussion is given in Smith (1991a; 1991b). 
Because the older climate records, those from the OLCC or even older, are poorly dated, 
comparison of paleoenvironmental events from a record at one site to events at another site is 
difficult if not speculative. Thus the level of past climate detail, such as the six observations 
given above about the YLCC in the Owens Lake Basin, is not available from the older records. 
However, aspects of the events seen in the younger part of the Owens Lake record can be 
identified in the older records. During the YLCC the coldest and highest effective moisture 
climate was interpreted, based on the ostracode and other records, as the third glacial (MIS 6) in 
the YLCC. Support for the interpretation, for example, comes from the MIS 6 lake in Death 
Valley that was at least 175 m deep, but only about 70 m deep during MIS 2 (Ku et al. 1998). 
If the OLCC and YLCC are similar, the third glacial period in the OLCC (MIS 16, from about 
680,000 to 630,000 years ago) is expected to have had the coldest and highest level of effective 
moisture in that cycle. Deciphering MAT or other climate characteristics from the OLCC is not 
straightforward from the available data, which mostly are lake levels. Lake level, as discussed 
above and by Smith (1991a), may be a product of higher MAP or colder temperature or some 
combination of both. Estimation of the general order of climate change magnitude from the size 
of old lakes does, however, provide insights to compare the climate characteristics of glacial 
periods within and between 400,000-year cycles. 
Reheis (1999, Figs. 2 and 3) presents evidence for MIS 16, the third glacial in the OLCC, being 
the biggest and deepest lake in several basins throughout the Great Basin. Knott (1999) 
identifies lake sediments deposited during MIS 16 (and perhaps a somewhat older lake) in Death 
Valley, but does not distinguish the possible size of the MIS 16 lake from others in the OLCC. 
Jannik et al. (1991) suggest a large lake existed in the Searles Basin during MIS 16 that was 
large enough toward the end of MIS 16 to overflow to the Panamint Basin. They also suggest an 
MIS 18 (about 725,000 to 705,000 years ago) lake may have overflowed to the Panamint Basin 
and that both of the latter lakes may have overflowed from the Panamint Basin to Death Valley. 
Similarly, Reheis (1999, Fig. 3) presents some evidence for a large lake during MIS 18. Oviatt 
et al. (1999) reinterpret the timing and occurrence of lakes in the Great Salt Lake Basin. They 
present chronological and environmental evidence from a core for a lake in that basin during 
MIS 16 and MIS 12 (about 490,000 to 415,000 years ago), but no others during the OLCC. 
Reheis (1999, Fig. 3) also presents evidence for a large lake during MIS 12, but not as large as 
the one during MIS 16. 
The MIS 16 lakes identified by Reheis (1999) are much larger and deeper than those from the 
same basins during MIS 6. Although shoreline elevations are not available, the opposite appears

 
61  
to be true for the lakes in the Great Salt Lake Basin (Oviatt et al. 1999). The differences in size 
between the MIS 16 and 6 lakes could be a result of various combinations of temperature and 
precipitation or simply a different average position of the polar jet stream due to spatial and 
height differences in the two continental ice sheets. The important aspect of this information for 
this discussion is that the apparent biggest lakes in the OLCC and YLCC occur during the third 
glacial in each cycle. The third glacial in each cycle would then seem to have had the highest 
effective moisture; whether that was generated largely due to cold temperatures, high 
precipitation, or both, is not known. 
Similarly, Reheis (1999, Fig. 3) suggests MIS 12 lakes also were large, but not as large as those 
during MIS 16. MIS 12 is in the same position in the OLCC as is MIS 2 in the YLCC, the last 
(4th) glacial cycle. Ku et al. (1998) show that the MIS 2 lake in Death Valley was large, but 
smaller than the MIS 6 lakes. Jannik et al. (1991) suggest that the Owens drainage lakes filled 
and flowed into Death Valley during parts of MIS 16, 12, and 6, among others, but not during 
MIS 2. The absolute size of a lake in a particular basin is a function of many climate and nonclimate 
factors, but what is important here is that in a given basin, the behavior of a sequence of 
lakes during the OLCC, that is, the lakes characterizing MIS 20, 18, 16, and 14/12, appears to be 
similar to the behavior of a sequence of lakes during the YLCC, that is MIS 10, 8, 6, and 4/2. 
Finally, the marine isotope record (Reheis 1999, Fig. 3) provides a general proxy for ice volume, 
although ocean temperature may also play an important and perhaps unknown role in this record. 
Marine isotopic profiles during the OLCC generally are similar to those during the YLCC. The 
largest ice sheets are those from MIS 16, 12, 6, and 2. As continental ice sheets expand in area 
and become higher in elevation they force the polar air masses to the south. So large ice sheets 
should result in cold and or wet climates in the vicinity of YM. Large ice sheets also result in 
climates in the YM area with cooler summers than today, thus enhancing effective moisture. 
Conversely, MISs 20, 18, 14, 10, 8, and 4 apparently had smaller or lower (?) ice sheets, 
potentially allowing for warmer, and thus lower effective moisture climates in the YM region, as 
perhaps the smaller lakes associated with those periods imply. 
The records of paleoclimate are often incomplete, poorly dated, and are interpreted differently by 
different workers. The information above, however, implies that there is some repetition 
between the types of climate in the OLCC and the YLCC. This provides the basis to suggest that 
the nature of the next glacial cycle at the beginning of the next 400,000-year cycle may be more 
like the glacials at the beginnings of the long climate cycles than other glacials within the long 
climate cycles. If so, then the transition from MIS 11 to MIS 10 provides a past analog for 
forecasting future climate change, and hence the basis used here to establish a potential climate 
scenario for the next 10,000 years. 
Although not based on paleoclimate data, the orbital parameters, especially precession and 
eccentricity, show strong similarity at the beginning of the YLCC and from now forward in time 
for the next 100,000 years, which is the beginning of a new 400,000-year cycle (Berger and 
Loutre 1991, DTN: GS000200005121.001; and GS000200005121.002) (compare Figures 7 and 
9). As has been discussed above, there is no certainty in whether or not orbital parameters that 
time climate change also drive climate change. If orbital parameters drive climate change, do 
they also determine the nature or magnitude of climate change? If the answer to the last question 
is yes, then position within the long orbital cycles also determines the nature of climate and thus 
the beginning of the YLCC is the analog for future climate during the next 10,000 years.

 
62  
6.6 A FUTURE CLIMATE ANALOG FOR THE NEXT 10,000 YEARS 
On the basis of the assumptions discussed above that 1) climate is cyclic, 2) climate can be timed 
with an orbital clock, 3) climate sequences repeat themselves in a predictable way, and 4) 
tectonics or other long-term climate-forcing functions that could result in non-cyclic future 
climate behavior are constant on the time scales of interest here, the MIS 11/10 transition was 
selected as the analog for future climate for the next 10,000 years. The timing of and nature of 
climate change for the next 10,000 years are discussed below. 
6.6.1 Timing of Climate Change for the Next 10,000 Years 
Forecasting the timing of future climate change simply requires the identification of a past 
climate sequence that is believed to be part of a cycle that will repeat itself in the future. Thus, a 
past climate time series analog is identified and projected into the future. Forecasting is very 
different from predicting. Predicting integrates all factors affecting Earth's climate into a timeseries 
numerical model that is then run for the particular future times under predetermined 
boundary conditions. Specifically, climate models require particular boundary conditions to 
operate properly. Boundary conditions would include ocean surface temperatures at some future 
point in time and of course if we knew with any certainty what future boundary conditions were 
then we would also know something about future climate and not need to do any modeling. 
Furthermore, climate models and the computers they run on can not produce output for long 
periods of time, such as 10,000 years. Typical output might be five years of data following long 
computer run times. Present-day science does not know with certainty why climate changes, or 
know how to numerically describe the change in climate system in a time series, nor is there any 
agreement about future boundary conditions. Consequently, the discussion below will focus on 
forecasting future climate. 
First a point representing the equivalent to the present day is identified in the YLCC series (a 
past/present point). Then the next 10,000 years of paleoclimate reconstruction from the 
past/present point becomes the future climate forecast. The orbital clock that was derived from 
the Devils Hole chronology (Section 6.4 above) provides the means to approximately identify the 
past/present point in the Owens Lake record. The graph (Figures 7a and 7b) shows the linkage 
of the present-day position in the orbital clock (I=1,000 years ago) and the equivalent point 
during MIS 11 (I=399,000 years ago). The orbital-clock relation is readily transferred to Devils 
Hole through their respective chronologies (see also Figure 8). 
A precession maximum in the Southern Hemisphere, used to time the beginning of climate 
change from an interglacial towards a glacial climate, occurred 399,000 years ago during MIS 11 
(Berger and Loutre 1991, DTN: GS000200005121.001). The first data point in the Devils Hole 
record (Landwehr et al. 1997, DTN: GS000200005121.003) indicating climate change away 
from the MIS 11 interglacial climate occurs at 397,300 years ago (ignoring the Devils Hole age 
standard deviation) or 1,700 years after the precession maximum. A precession maximum in the 
Southern Hemisphere during the present interglacial climate occurred 1,000 years ago (Figure 
7b). Using the MIS 11/10 timing indicates the beginning of climate change away from the 
present interglacial may be about 700 years in the future. Therefore, what will the climate of the 
next 700 years and beyond be like and what will be the timing of those future changes in 
climate?

 
63  
Placement of a past/present point in the Owens Lake sedimentary record requires that the 
sedimentary chronology be placed in the context of the Devils Hole chronology. The Owens 
Lake chronology, as discussed above in Section 6.5, is based on a sediment mass-accumulation 
curve. Figure 11 shows a possible correlation of the Owens Lake sedimentary record (DTN: 
GS970708315121.002, GS991008315121.001) to the MIS periods. By correlation with the 
chronology of the Devils Hole d18O record (Landwehr et al. 1997, DTN: GS000200005121.003), 
the Owens Lake MIS periods are given an absolute chronology. Applying the Devils Hole 
chronology to the Owens Lake record indicates the sediment accumulation ages at Owens Lake 
are variously too old or too young or about correct in a few instances such as the MIS 11/10 
interval. This implies the mass-accumulation rate clock variously runs too fast or too slow, and 
occasionally is on time. Nonetheless, the correlation between the Owens Lake record and Devils 
Hole does place the approximate position of the transition between MIS 11/10 in the Owens 
Lake record in Devils Hole terms. 
Placement of the Owens Lake sedimentary record in the Devils Hole chronology, unfortunately, 
only approximates where the past/present point belongs. In order to further refine the Owens 
Lake age estimates, the ostracode and diatom data (DTN: GS970708315121.002, 
GS991008315121.001, GS970708315121.001, GS991008315121.002) in the Owens Lake record 
are used to identify environmental change during and from the MIS 11 interglacial, and then 
from the sequence of environmental change, to estimate where the past/present point belongs. 
Inspection of the stratigraphic distribution of ostracode species in Figure 11 shows a sequence of 
ostracode species from about 425,000 years ago (Owens Lake chronology) to about 405,000 
years ago starting with Candona caudata, followed by Limnocythere ceriotuberosa, and ending 
with L. sappaensis. The interpretation of this ostracode sequence (Section 6.5) indicates a 
transition from a full and spilling lake during a glacial or glacial-transition climate (C. caudata) 
to an intermediate climate between glacial and interglacial (L. ceriotuberosa), to an interglacial 
climate (L. sappaensis). Similar ostracode sequences occur at the ends of other glacials 
including the last one (Figure 11). 
During MIS 11 the abundance peaks of Limnocythere sappaensis at about 405,000 years ago 
(Owens Lake chronology) are followed by abundant Limnocythere bradburyi at about 403,000 
years ago (Owens Lake chronology) (also present around 410,000 years ago, Owens Lake 
chronology) (DTN: GS970708315121.002, GS991008315121.001). L. bradburyi does not occur 
in the Owens Lake record at the transition into the present interglacial, but was very common in 
several basins from the southwest, such as the San Agustin Basin (Markgraf et al. 1984). The 
appearance of L. bradburyi indicates a period of intense summer monsoon activity (Section 6.5). 
Various saline benthic diatoms co-occur with Limnocythere sappaensis (DTN: 
GS970708315121.002, GS991008315121.001, GS970708315121.001, GS991008315121.002) 
from its first appearance in MIS 11 until about 405,000 years ago (Owens Lake chronology). 
From about 405,000 to 403,000 years ago (Owens Lake chronology) the sediments are barren of 
diatoms. Because diatoms are made of opal and opal dissolves in alkaline water, the absence of 
diatoms and the presence of a saline, alkaline ostracode implies the latter interval of time was 
one where Owens Lake was both very saline and very alkaline. When L. bradburyi appears at 
403,000 years ago (Owens Lake chronology) it co-occurs with saline benthic and planktic 
diatoms, implying a saline lake, but one that is both fresher than the one without diatoms, and 
also one that is deeper. A fresher and deeper lake, if derived from snowpack, should have cold 
climate ostracodes, such as L. ceriotuberosa without L. bradburyi, as is typical of much of the

 
64  
Owens Lake record. The presence of planktic saline diatoms, and L. bradburyi imply a 
significant summer rain input to the lake, perhaps with limited or no winter-precipitation-derived 
surface-water flow. 
The Holocene lake core (MIS 1) contains abundant Limnocythere sappaensis through about 
4,000 or 5,000 years ago radiocarbon time, followed by a core containing salt and few to no 
ostracodes (Smith and Bischoff 1997). Recent historic records also report the existence of a 
saline, alkaline lake before the Owens River was diverted to Los Angeles. The climate associated 
with MIS 11 therefore is similar to that of MIS 1, but there are also differences. MIS 1 in 
particular has no L. bradburyi at its beginning, and L. ceriotuberosa is much more common in 
MIS 1, implying it was cooler and perhaps wetter than MIS 11. 
Presuming that climate is cyclic, then the past/present day point in the MIS 11 sequence at 
Owens Lake is above the large L. sappaensis abundance peak (labeled 220.0), but below the L. 
bradburyi peaks (DTN: GS970708315121.002, GS991008315121.001). The argument is that 
the large L. sappaensis abundance peak in MIS 11 reflects a mid-stage warm, dry climate and the 
enhanced monsoon reflecting the L. bradburyi abundance peak has yet to occur in MIS 1. 
Because the present interglacial is nearing its end, the modern climate state should be close to the 
proposed monsoon. Accordingly, the past/present point was placed closer to the monsoon 
climate indicator than to the interglacial climate indicator, at an Owens Lake chronology age of 
403,970 years ago (see Figure 14). Comparison of the diatom record from MIS 11 and 1 (DTN: 
GS970708315121.001, GS991008315121.002) leads to a similar conclusion as that derived from 
the ostracode data.

 
65  
Figure 14. Stratigraphic Distribution of Ostracodes in Part of the Owens Lake Record Used for the Future Climate Analog 
DTN: GS970708315121.002, GS991008315121.001, GS000208315121.002

 
66  
From the past/present point at Owens Lake, the timing of the climate change intervals is forecast 
on the basis of the abundance intervals for the ostracode species (DTN: GS970708315121.002, 
GS991008315121.001). The time between the sample in the L. sappaensis abundance peak 
403,970 years ago and the first appearance of L. bradburyi is about 600 years in Owens Lake 
time, the length of modern-like climate remaining before the enhanced monsoon climate begins 
(Table 2). In turn, the length of the L. bradburyi interval of monsoon climate is about 1,400 
years in Owens Lake time (this includes the interval above L. bradburyi containing abundant L. 
sappaensis) (Figure 14). The monsoon interval is followed by more than 8,000 years of glacialtransition 
climate represented by the Candona caudata interval, thus completing the 10,000 years 
for the future climate analog (Figure 14). 
Table 2. Meteorological stations selected to represent future climate states at Yucca Mountain, Nevada 
Climate 
State Duration 
Representative 
Meteorological 
Stations 
Locations Of 
Meteorological Stations 
Modern 
Interglacial 
Climate 
400 to 600 years Site and regional 
meteorological stations Yucca Mountain region 
Monsoon 900 to 1,400 
Average Upper Bound: 
Nogales, Arizona 
Hobbs, New Mexico 
North Latitude West Longitude 
31 21' 110 55' 
32 42' 103 08' 
Climate Years Average Lower Bound: 
Site and regional 
meteorological stations 
Yucca Mountain region 
Glacial 
Transition 8,000 to 8,700 
Average Upper Bound: 
Spokane, Washington 
Rosalia, Washington 
St. John, Washington 
North Latitude West Longitude 
47 38' 117 32' 
47 14' 117 22' 
47 06' 117 35' 
Climate Years Average Lower Bound: 
Beowawe, Nevada 
Delta, Utah 
North Latitude West Longitude 
40 35' 25" 116 28' 29" 
39 20' 22" 112 35' 45" 
The timing of the climate episodes noted above are based on the Owens Lake sediment massaccumulation 
curve that was derived for the entire core. As discussed above the massaccumulation 
curve gives an average chronology at best and in many places in the core the 
average accumulation rate of sediment may not be a good indicator of elapsed time. The average 
sediment-accumulation rate is about 40 cm per 1,000 years (Smith and Bischoff, 1997), and is 
the basis for the times listed in the paragraph above and in Figure 14.

 
67  
The study by Litwin et al. (1999), which focuses on the upper part of the core, suggests that the 
sediment accumulation rates during dry climate periods are much higher than during wet climate 
periods. In Litwin et al. (1999) they estimate accumulation rates for interglacial, glacial, and 
transitions between interglacial and glacial climates. The future climate analog (MIS 11/10) 
deals with interglacial and glacial-transition climates. However, the part of the core that should 
be considered in terms of different accumulation rates is the interglacial, as the glacial-transition 
climates extend well beyond the 10,000-year limit discussed here. Litwin et al. (1999) estimate 
that interglacial climate sediment accumulation rates from MIS 1 and 5 are 60 and 66 cm per 
1,000 years, respectively. These values provide an alternative accumulation rate for the 
interglacial periods in Owens Lake to the approximately 40 cm per 1,000 years massaccumulation 
rate for the entire record. 
The sediment accumulation rates for interglacial climates noted above average about 63 cm per 
1,000 years. There is no way of knowing if the MIS 11 interglacial had a similar sediment 
accumulation rate, but given that the rates for MIS 5 and 1 are similar, it is reasonable to assume 
such a rate might apply to MIS 11. If the higher rate of sediment accumulation does apply, then 
the timing of climate change derived from it is more probable than that derived from a uniform 
rate of sediment accumulation. Applying a rate of 63 cm of sediment accumulation per 1,000 
years to MIS 11 results in an alternative timing for the three climate states of: 
1. Modern-like for about 360 years, rounded to 400 years, 
2. Monsoon for about 895 years, rounded to 900 years, and 
3. Glacial transition for about 8,700 years (10,000 minus 400 minus 900). 
A modern-like or warmer than modern-like climate for about 1,300 years before entering a 
glacial-transition climate is similar to the estimate previously discussed (700 years) based on a 
comparison of precession and the Devils Hole record. It is also similar to Imbrie and Imbries 
estimate (1986, p. 183-184) that earth's climate should become progressively warmer for about 
the next 1,000 years due to an increase in solar output, and then begin to cool due to 
Milankovitch forcing. 
Combining the above estimates for the timing of future climate change derived from the different 
estimates of sediment accumulation rates results in the following forecast for timing of climate 
changes. A modern-like climate should persist for about 400 to 600 years after present. The 
modern-like climate will be followed by a monsoon climate that will last from about 900 to 
1,400 years after present and that climate will be followed by a glacial-transition climate that will 
persist through the remainder of the 10,000-year period at YM. 
Other factors that may impact the timing of the three climate states include the standard 
deviation associated with the Devils Hole ages, the uncertainty of the exact time when the Devils 
Hole record implies climate is changing, the uncertainty of exactly where the past/present point 
is in the Owens Lake record (analog climate proxy record), and the uncertainty of climate change 
itself. The standard deviations about the mean of the Devils Hole ages are, by their nature, an 
estimate of uncertainty. That estimate was not incorporated into the analysis, in part, because the

 
68  
other sources of uncertainty can not be estimated and hence their relation to standard deviation is 
unknown. 
The uncertainty of the exact time when the Devils Hole record is beginning to change implies 
climate has two components. The first component involves the uncertainty of knowing if the 
beginning of a change in the isotope values in the recharge area are directly correlated with 
changes in MAP and MAT or other climate parameters. There could be a lead or a lag between 
change in regional climate parameters and a record of recharge at Devils Hole. The second 
component involves the nature of the Devils Hole samples themselves. Each sample integrates a 
particular thickness of carbonate in a continuous sample series and represents about 1,000 years 
(Winograd et al. 1992). Consequently, any rapid change in the recharge recorded at Devils Hole 
could occur anytime within the 1,000 years. 
Placement of the past/present point in the Owens Lake record is a matter of interpretation, and 
has an unknown level of uncertainty associated with it. Because this uncertainty could be large 
or small it may compound or limit the effects from obtaining time from the estimates of sediment 
accumulation. 
The final source of uncertainty comes from the chaotic nature of the climate system itself 
(Stanhill 1999). The latter may be compounded with unknown effects of human activity on 
climate change. The climate proxy records throughout the Owens Lake cores show various 
degrees of variability that may well reflect decade- or century-scale variability that may or may 
not have significance to the timing of climate change on the multi-century or millennia time 
scales. 
The above sources of uncertainty could sum together to create a large uncertainty or could cancel 
each other out so as to create a smaller uncertainty. Unlike the different estimates of sediment 
accumulation rates, there is no simple or objective way of assessing the nature of the above four 
sources of uncertainty as it might apply to the future. 
6.6.2 The Nature of Future Climate Change 
The nature or characteristics of future climate, but especially the annual and seasonal 
characteristics of precipitation and temperature, provide the input terms to the infiltration model 
(USGS 2000) whose output feeds the unsaturated zone flow and transport process model report 
(PMR). The nature of future climate, as discussed below, is forecast in terms of an upper bound 
and a lower bound. Upper- and lower-bound values are given here because: 1) they are needed 
for the models and 2) given the numerous uncertainties (Sections 6.3, 6.4, and 6.5) in the record 
of turning climate proxy data into climate values, establishing possible bounds is more defensible 
than establishing means, especially means that are applied to long periods of time. Because the 
infiltration model (USGS 2000) requires annual and seasonal climate values to run properly, the 
upper- and lower-bound values are established with meteorological stations, selected as 
representative of the climate. Stations with complete and long records were given priority. 
The past climate history proposed as the timing for the future climate analog (Section 6.6.1) is 
composed of three climates, each characterized by particular species assemblages of ostracodes 
(DTN: GS970708315121.002, GS991008315121.001). When necessary, the ostracode 
assemblage interpretations are supported by interpretations of the diatom assemblages (DTN:

 
69  
GS970708315121.001, GS991008315121.002). The modern-like climate interval is 
characterized by Limnocythere sappaensis and is forecast to persist for the next 400 to 600 years. 
The second climate interval is characterized by a mixture of L. bradburyi and L. sappaensis and 
is forecast to persist for about 900 to 1,400 years after the first climate interval. The third and 
last climate interval is characterized by Candona caudata as well as rare occurrences of L. 
sappaensis. The third climate interval also is characterized by the diatom Stephanodiscus 
asteroides, and diatom species belonging to Campylodiscus spp. and Anomoeneis spp., based on 
the data collected by J. Platt Bradbury (DTN: GS970708315121.001, GS991008315121.002), 
and is forecast to persist for the remainder of the 10,000-year period. 
The modern-like climate interval is an interval of time when Owens Lake was supported by 
ground-water discharge, and an Owens River that was predominately at base flow. Summers are 
warm to hot and very evaporative with evaporation greatly exceeding precipitation at low 
elevation. Snowpack at high elevation is typically low to moderate, because the polar front does 
not remain fixed at a southerly position during the winter, and so does not set up a storm wave 
train that moves Pacific moisture over the Sierra Nevada Mountains (see discussion in Section 
6.2). Consequently with low snowpack, surface-water flow in the Owens River is usually low 
and seasonal. Owens Lake remains saline and at a low lake level for long periods of time. 
Precipitation, whether as rain or snow, is typically recycled to the atmosphere by evaporation or 
used by the local vegetation. 
The wettest years, which represent the upper-bound moisture regimes during modern-day 
climate, will typically be years when Pacific air flow is focused towards the high Sierra 
Mountains, increasing snowpack and hence the seasonal duration of surface-water flow in the 
Owens River and its potential to dilute or flush Owens Lake, thus diluting the salt content. Such 
climates also focus Pacific moisture towards southern Nevada, such as the El Nino climates that 
have been common during the last couple of decades. Dry years, which represent the lowerbound 
moisture regimes during modern-day climate, will be those years with minimal winter 
precipitation, typically years when the polar front remains largely north of the region and 
summer precipitation is dominated by subtropical high activity, but not to the degree necessary 
to generate a monsoon-type climate. 
Meteorological data for the upper and lower bounds come from available stations in the region, 
including YM project and non-project data (see Figure 15, Table 2) (USGS 2000). Regional 
averaged meteorological data from the National Oceanic and Atmospheric Administration 
(NOAA) reported in Thompson et al. (1999c, Figures 16 and 17) indicate that areas largely north 
of YM within central Nevada have had a range of MAP from about 75 mm to one value as high 
as 360 mm for the period of record (about 100 years). Similarly, from the same data sets, areas 
largely south of YM have had a range of MAP from less than 50 mm to one value as high as 325 
mm for the period of record. Notably, there are more low values than extremely high values, that 
is, the typical value is in the lower half of the range. By contrast, MAT in both regions falls into 
a smaller range of about 4 oC, or about 16 to 20 C for the area south of YM and about 8 to 12 C 
for the area north of YM (Thompson et al. 1999c, Figures 16 and 17).

 
70  
Figure 15. Meteorological Stations Selected (Table 2) to Represent Future Climate States at Yucca 
Mountain, Nevada

 
71  
Because climate is a regional phenomenon and climate is the primary driver of hydrology, the 
climate that creates the environmental characteristics defined above for Owens Lake also must 
be more or less the climate that exists at Yucca Mountain. So a hot and dry climate at YM is 
consistent with a saline Owens Lake supported largely by base flow. Owens Lake hydrology 
therefore is a direct proxy for climate at YM. 
The second climate interval, the monsoon climate, is characterized in the Owens Lake record by 
a mixture of Limnocythere bradburyi and L. sappaensis (DTN: GS970708315121.002, 
GS991008315121.001). Because L. bradburyi has a lower salinity tolerance than L. sappaensis 
(Forester 1983; Forester 1985) and does not appear to be tolerant of cold winters (Smith and 
Forester 1994), its existence in Owens Lake must imply a relatively lower TDS (less than about 
10,000 mg/L) and a source water derived from something other than snow melt. Surface flow 
derived from snow melt itself probably is not a problem for L. bradburyi, but rather the cold 
winter climates that generate the snowpack are a problem for this species. The hydrology of 
Owens Lake is strongly linked to winter precipitation and hence dilute deeper lakes are due to 
seasonal to annual flow derived from snowpack (see Section 6.5). From Figures 12 and 13 as 
well as discussion in Section 6.5, an expansion and intensification of the summer rain system, 
that is a stronger monsoon sufficient to generate diluting surface flow in the Owens River, is the 
simplest way to explain the occurrence of this species. The diatoms that occur during the L. 
bradburyi interval include saline planktic species, implying the lake is deeper, and less alkaline 
during this period. The diatom paleoenvironment is consistent with that implied by L. bradburyi. 
Accordingly, an analog meteorological station(s) for the L. bradburyi monsoon climate must be 
found to the south of Owens Lake today in either Mexico or the southernmost U.S. An analog 
from either Mexico or the southernmost U.S. would fulfill the taxon's temperature requirements 
and identify sites whose primary precipitation falls in the summer season. The level of 
precipitation has to be higher than modern-day Owens Lake MAP in order to maintain a lower 
salinity lake that is supported largely by summer precipitation within the modern warm 
evaporation regime. Summer rain and associated cloud cover would tend to lower evaporation 
relative to today. Historic records of MAP from Haiwee Reservoir 11 km south of Owens Lake 
show that summer rain dominated the annual precipitation during the years 1963, 1976, and 
1977, with MAP levels amounting to 270 mm, 251 mm, and 208 mm respectively (U.S. 
Department of Commerce 1964; 1977; 1978). During those years flow in the Owens River was 
minimal, (CRWMS M&O 1998, Figure 4.2-15). So those levels of MAP were not sufficient to 
create the deeper and slightly saline lake that the ostracode and diatom proxies imply existed 
during the monsoon climate. 
Considering the above climate conditions, the available meteorological data, and the region in 
which Limnocythere bradburyi occurs now, the station closest to the occurrence of the taxon in 
the U.S. is the one at Lordsburg, New Mexico with an MAP of 284 mm (DTN: 
GS000100001221.001). An MAP value of only 284 mm per year at Lordsburg is sufficient only 
to support an ephemeral playa and from the Haiwee Reservoir meteorological data above is less 
than values that resulted in limited flow in the Owens River. Sites in central Mexico where the 
taxon lives commonly have MAP values above 500 mm and as high as 2,000 mm (Forester 
1985). Remarkably, despite the latter very high levels of MAP, the Mexican lakes in which the 
taxon lives are typically shallow, if not ephemeral, and slightly saline, reflecting the very high 
levels of evaporation. Presumably the L. bradburyi regions in central Mexico would be poor 
analogs for Owens Lake, because these lower latitude sites have a much higher solar input, thus

 
72  
creating a different climate-lake-evaporation regime than would have existed at Owens Lake in 
the past. 
Selection of a monsoon climate analog site(s) must then come from the southern U.S. An upperbound 
value for the monsoon climate presumably must be a higher value than any of the values 
from Haiwee Reservoir, and MAT must remain as high or higher than Owens Lake today. 
Within the region in the U.S. that experiences a strong summer monsoon and where 
Limnocythere bradburyi lives, there are two meteorological stations with long, complete records 
that have consistently higher levels of MAP than Haiwee Reservoir: the station at Hobbs, New 
Mexico and the station at Nogales, Arizona, with MAP levels of 418 mm and 414 mm, 
respectively (DTN: GS000100001221.001). Two stations are selected to minimize the influence 
of local meteorological phenomena on the input to the infiltration model (USGS 2000) (Figure 
15, Table 2). The MAP at these sites may not be high enough to generate the appropriate lake in 
the Owens Basin, but within the available modern meteorological data, these are the best choices 
available. Because Limnocythere sappaensis exists throughout the climate interval and at some 
horizons is the only ostracode (DTN: GS970708315121.002, GS991008315121.001), the 
conditions at YM today are representative of the dry lower bound for the monsoon climate. The 
meteorological stations selected for the lower bound for the monsoon climate are those from the 
YM region today (USGS 2000). 
The monsoon climate, from the analogs, is a climate where winter precipitation exists, but does 
not dominate MAP. The lesser importance of winter precipitation means that winter air masses 
are also of less importance, and thus the winter season is likely warmer than today and hence 
more evaporative. The annual transition from the winter season to the wet summer season would 
be hot and dry as is true of most seasonal transitions to a monsoon climate. Summer rain would 
then expand northward either due to a monsoon land-to-ocean circulation or to the northward 
migration of the subtropical easterlies, that is, the trades. Intense summer rain, unlike today, 
would be sufficient to sustain flow into Owens Lake to maintain a moderate-sized and slightly 
saline lake at least on a seasonal basis. Climate during this period would vary from episodes of 
intense summer rain to modern-like climates with relatively more winter and less summer 
precipitation. The intense summer rain periods would necessarily be periods with extensive 
cloud cover whereas summers with lesser rain and winter seasons would have limited cloud 
cover. 
An expansion of the summer rain regime to the Owens Basin region also would have expanded 
well north of YM (Figure 13). Because YM would be more centrally located within such a 
summer rain regime it may experience upper-bound levels of MAP that are higher than those 
identified above from the analog meteorological stations. 
The third climate, the glacial-transition climate, is characterized by the appearance of Candona 
caudata (DTN: GS970708315121.002, GS991008315121.001) as well as by the diatom 
Stephanodiscus asteroides, and diatom species belonging to Campylodiscus spp. and 
Anomoeneis spp. (DTN: GS970708315121.001, GS991008315121.002). The change from the 
monsoon climate to the glacial-transition climate is rapid, assuming no unconformities in the 
Owens Lake record, occurring within 100 to 200 years (Smith and Bischoff 1997). The 
magnitude of the climate change was as large as it was fast, shifting from a strong monsoon 
system dominated by summer precipitation to a winter regime with sufficient effective moisture 
to sustain a fresh and spilling Owens Lake.

 
73  
Candona caudata lives in the Owens Lake area today as well as in many places north of Owens 
Lake including sites within Canada and Alaska. In the Owens Lake area it lives in the Owens 
River as well as in freshwater lakes at higher elevation, and thus is tolerant of the regions 
seasonal temperature variability, but is not tolerant of saline water that would be typical for 
Owens Lake today under natural conditions. Candona caudata only enters Owens Lake when 
the TDS falls and remains below about 3,000 mg/L (Bradbury et al. 1989), and that typically 
implies the lake is full and spilling. The presence of Stephanodiscus asteroides, a cool and 
freshwater planktic diatom (DTN: GS970708315121.001, GS991008315121.002), also implies a 
deep spilling lake. Conversely, the sporadic appearance of Limnocythere sappaensis (DTN: 
GS970708315121.002, GS991008315121.001) as well as the diatoms Campylodiscus spp. and 
Anomoeneis spp. imply there were also episodes during this climate period that were relatively 
warm and dry, thus demonstrating some degree of climate variability. 
As described above (Section 6.5), for the lake to be full and spilling the polar front must be 
resident in the region during much of the winter, both lowering MAT and hence evaporation, and 
increasing snowpack, and hence surface flow to the lake. The genesis of greater snowpack with 
a resident polar air mass must also lower MAT and increase MAP at YM. The cooler climate, 
however, never becomes very cold with a high effective moisture as was true of the last two fullglacial 
periods. The ostracodes and diatoms implying warm dry climates do not persist 
throughout the Owens Lake record thus indicating the warmth is not seasonal summer warmth, 
as is true of the modern climate, but rather represents warm episodes within a generally cool and 
wet period. The climate during the glacial-transition period was typically a cool, usually wet 
winter season with warm (but not hot) to cool summers that were usually dry relative to the 
modern day summers. 
Selecting upper- and lower-bound meteorological stations for the glacial-transition climate must 
identify sites with cool winter wet seasons, and warm to cool and dry summers, so areas north of 
the summer rain regime shown in Figure 13. Further, if possible, the analog sites should lie on 
the east side of large mountain ranges, and hence in the rain shadow of those ranges. The 
absence of Cytherissa lacustris, (DTN: GS970708315121.002, GS991008315121.001) the 
ostracode implying cold Canadian-like climate, implies the upper-bound analog lies within the 
contiguous U.S. 
The analog station(s) presumably should be areas with some or all of the common ostracodes and 
diatoms found in Owens Lake (DTN: GS970708315121.002, GS991008315121.001, 
GS970708315121.001, GS991008315121.002), thus potentially integrating the biology, 
hydrology, and climate linkages that were expressed in the past at Owens Lake. The study by 
Thompson et al. (1999c) suggests the MAT at YM during the last full-glacial period was about 
8oC and during that period Cytherissa lacustris was common in Owens Lake. Thus the MAT for 
the glacial-transition climate should be no colder than and preferably warmer than 8oC. Finally, 
the analog station(s) should be in the semi-arid west, because, although the glacial-transition 
climate is wetter and cooler than the interglacial climates, effective moisture is still negative, as 
is true for all of the glacial and glacial-transition climates at Owens Lake and YM. 
The meteorological station(s) representing the glacial transition upper bound should be in a place 
with a higher MAP than periods of high Owens Lake discharge derived from winter precipitation 
during the historic period. One of the highest discharge years for the Owens River (CRWMS

 
74  
M&O 1998, Figure 4.2-15) was in 1969 and the MAP at Haiwee, just south of Owens Lake, was 
309 mm (U.S. Department of Commerce 1970). Surface flow in the Owens River is primarily 
influenced by snowpack in the Sierra Mountains, not by high winter MAP near Owens Lake, 
unlike times of high summer MAP when surface flow is dominated by summer rain. 
Nonetheless, high snowpack years also correspond to high MAP from winter precipitation at 
Owens Lake (Forester et al. 1999; CRWMS M&O 1998, p. 4.2-16 to 4.2-18). Accordingly, the 
upper-bound meteorological site(s) should have higher MAP than 309 mm, because even the 
high historic discharge levels are not sufficient to fill and spill the lake as implied by the diatoms 
and ostracodes. Because the fill and spill of Owens Lake is believed to be related to the 
seasonal, if not the annual, residence of the polar front (see Section 6.2), then the upper-bound 
meteorological station should logically be selected in an area where in today's climate the polar 
front resides through most or all of the winter season and where its average position resides most 
of the year. 
Given all of the above qualifying conditions, the upper-bound glacial-transition meteorological 
site is selected in the northwestern U.S. east of the Cascades for several reasons. The region lies 
east of a high mountain range, and thus falls within a rain shadow as does YM. The regional 
MAP is winter-precipitation dominated, and is under the influence of the polar front during the 
winter as well as being situated near the average position of the polar front throughout the year. 
Furthermore, unlike localities farther north in Canada, the region does not experience extended 
dominance by the very cold Arctic high-pressure air, typical of the cold, full-glacial periods. A 
number of meteorological stations in the region have MAP values well above 300 mm (U.S. 
Department of Commerce 1970), which in todays temperature regime in the Owens Basin only 
supports a saline lake. The regional values of MAT are on the cool side, but several stations are 
above the 8oC values considered to be a lower limit for the glacial-transition climate (Thompson 
et al. 1999c). The diatoms and ostracodes common to the glacial-transition interval in Owens 
Lake are known to live in lakes in the region such as Sprague Lake, Washington. Thus lakes in 
the region contain a common biology, hydrology, and climate linkage with the paleolake in the 
Owens Basin. 
Examination of the meteorological station data from eastern Washington (DTN: 
GS000100001221.001) both in the context of the above considerations and in terms of length 
and completeness of record provides three stations that fit all of the criteria for the upper-bound 
glacial-transition climate (see Figure 15, and Table 2). The stations, Spokane, Rosalia, and St. 
John, are all close to each other, but do not have identical records, presumably reflecting local 
differences in MAP and MAT. As in other cases, selecting multiple meteorological stations is 
intended to minimize local effects on the climate parameters used as input to the infiltration 
model (USGS 2000). 
The meteorological stations representing the lower-bound glacial-transition climate should be in 
a place where MAT is higher than for the upper bound and thus most will be south of the upperbound 
localities. The MAT should, however, be lower than that for the Owens Lake Basin today 
so that effective moisture levels are higher consistent with a fill and spill lake. The stations 
should have a lower MAP than the upper-bound sites, because the record from the Owens Lake 
Basin shows episodes when either saline diatoms or ostracodes or both are present implying less 
surface flow in the Owens River. The absence, however, of abundant saline taxa implies 
effective moisture is higher than modern day and that likely reflects cooler than modern-day 
MAT values rather than high MAP values. So the lower-bound meteorological sites may have

 
75  
MAP values that are similar to or even lower than modern-day Owens Lake Basin. As with the 
upper-bound meteorological sites, the region should be winter precipitation dominated, should be 
north of the summer rain regime (Figure 13), and have some or all of the ostracode or diatom 
species found in the fossil record at Owens Lake. 
Inspection of meteorological sites that fit these conditions reveals that there are few choices 
available. The one set of meteorological data that fits all of these criteria and also has a long and 
complete record is found at Delta, Utah (DTN: GS000100001221.001), and thus that site is 
selected as one of the lower-bound sites (Figure 15, Table 2). The site at Beowawe, Nevada 
(DTN: GS000100001221.001), was added as a lower-bound meteorological station, again to 
avoid the potential of using a single site for input into the infiltration model (USGS 2000) 
(Figure 15, Table 2), because its meteorological data meet most of the requirements noted above. 
The upper-bound MAP values for the monsoon and the glacial-transition climates are only 
slightly higher than the modern high values from the region. Thompson et al. (1999c) show the 
NOAA data for region 3, generally north of YM, and region 4, generally south of YM. The latter 
data show upper-bound values in the mid-300's of mm and numerous values in the low 300's of 
mm. Thus selection of meteorological stations having upper-bound values in the low 400's of 
mm implies that the future climate states are only somewhat wetter than the modern climate. 
The lower-bound MAP value, selected as a future climate analog for the glacial-transition 
climate, is much higher than the modern lower-bound values reported for regions 3 and 4 (see 
Thompson et al. 1999c). Similar to the lower-bound glacial-transition value for MAP, the values 
of MAT for the glacial-transition analog climate are much lower than the MAT values in the YM 
and Owens Lake region today (Thompson et al. 1999c and DTN: GS000100001221.001). Thus 
the apparent principal differences between the modern-day climate and the glacial-transition 
climate upper and lower bounds are that the latter climates are not as dry nor as warm as modern 
day, that is, the biggest differences from today are in the lower-bound values, not the upperbound 
values. MAT and its impact on evaporation and hence on effective moisture would seem 
to affect the future climate analog more than gains in MAP.

 
76  
7. CONCLUSIONS 
The analysis of future climate change in this AMR consists of examining the paleoclimate record 
in order to find a past climate sequence on which to base extrapolation of future climatic 
conditions in the Yucca Mountain region. Four key assumptions are discussed: 
1. Climate is cyclical over 400,000-year periods and the earth is at the beginning of the 
next 400,000-year cycle. Climate cyclicity is important for forecasting future climate 
because it implies some past climate or aspects of past climate will recur in the future. 
2. Climate change can be timed with an earth-orbital clock of precession and 
eccentricity, so the timing of future climate change can be estimated from the orbital 
clock. Timing climate change with a clock that can be set accurately in the future is 
important for forecasting climate, because it allows for an accurate assessment of 
future climate durations used as input by TSPA and infiltration (USGS 2000) models. 
Cycles of glacial and interglacial climates occur about every 100,000 years. 
3. Past glacial/interglacial climates differ from each other, and the nature of particular 
past climates should repeat themselves in a predetermined order. Thus the analysis 
can focus on one particular climate sequence rather than all past climates and need 
not take the conservative approach of using the climates that generate the highest 
infiltration as being those expected in the next 10,000 years. 
4. Long-term earth-based climate-forcing functions, such as tectonic change, have 
remained relatively constant over the past 500,000 years or so and will remain 
constant for the next 10,000 or more years. This is important to climate forecasting 
because such forcing functions change climate in non-cyclic ways, so if they were not 
constant the first three assumptions would be invalid. 
From the discussion of the above four assumptions, which are intended to establish a defensible 
means for climate forecasting, the Owens Lake climate record is used to describe the climate 
conditions of the interval selected as the past/future climate analog. The past/future climate 
analog shows three distinct climates each of which are described in terms of an upper-bound and 
a lower-bound climate value. The upper and lower bounds of each climate are described from 
what are believed to be representative analog meteorological stations (Figure 15, Table 2) and 
the data at those stations then serve as input to the infiltration model (USGS 2000). Although 
other stations might have been selected as more representative of the upper and lower-bound 
climate conditions, it is more likely that the way the climate interpretations are used by the 
infiltration model impacts the amount of infiltration more than differences between particular 
meteorological stations would impact the amount of infiltration. 
The past/future climate analog forecasts that during the next 10,000 years at YM the modern-day 
climate should persist for 400 to 600 years, followed by a warmer and much wetter monsoon 
climate for 900 to 1,400 years, followed by a cooler and wetter glacial-transition climate for the 
remaining 8,000 to 8,700 years. The range of ages represents uncertainty in the sediment 
accumulation rates in Owens Lake during the climate analog period. 
The upper-bound precipitation values for the monsoon and glacial-transition climates exceed the 
upper bounds of the regions modern-day climate (see Thompson et al. 1999c, Figures 16 and 
17) by about 100 mm. The glacial-transition climate's lower bound exceeds the modern lowerbound 
values by about 150 mm (see discussion Section 6.6.2). Thus the future climate based on

 
77  
this method of analysis is wetter, but not substantially wetter than the modern climate. 
Temperature, however, defines an important difference between the modern climate and the 
glacial-transition climate. The glacial-transition climate is cooler than the modern climate, so 
evaporation is substantially lower than during modern times. A lower level of evaporation 
means that precipitation will be more readily stored, and hence available for infiltration, than in 
today's climate. 
Forecasting future climate was selected rather than modeling future climate because climate 
modeling, among many complications, requires that the future climate boundary conditions be 
known for input to the model. If the future climate boundary conditions were known with 
confidence, then there would no longer be the need to model climate or the need would be 
diminished. Because future boundary conditions are not known, a climate model must either use 
the modern-day values or estimates of the future values and in either case, the value of the output 
from such a model would have limited value in terms of defensibility. 
Forecasting the future by using a past climate sequence to bound the future also has many 
uncertainties, such as 1) differences in the selection of a particular past sequence to forecast the 
future, 2) the chaotic nature of climate (Stanhill 1999), and 3) the possibility that human activity 
may change the climate system in a way that will change the cyclical patterns. Therefore, in this 
analysis, the rationale for a particular past climate is described, and the method is then applied to 
acquire possible future climate values. Nonetheless, other arguments can be made for using other 
past climate sequences as an analog for the next 10,000 years. Like the one presented in this 
AMR, these other arguments would have evidence to support them. Uncertainties associated 
with the potential for forecasting future climates with different past climates is a consequence of 
the uncertainty of future climate itself, and of the uncertainty associated with depicting future 
climate by extrapolation of particular past climates into the future. Because there are many past 
climates that may or may not repeat in the future, and because forecasting is extrapolation, the 
future climate forecasts given in this AMR, or any other forecast, must by their very nature have 
some substantial, but indeterminate, level of uncertainty associated with them. Similarly, if 
climate is wholly chaotic, then it might not be cyclic and so the past might not provide a basis to 
understand the future. Human activity might enhance chaotic behavior within the climate 
system. Despite all of the uncertainties, it is contended that the analysis in this AMR is 
reasonable, that it is based on a consistent interpretation of available data, and so is defensible. 
That is, defensible in the sense that the analysis is based on a body of data and a reasonable 
possibility rather than that the climate forecast by this analysis is much more likely to occur 
relative to other possible methods. There are no other uncertainties than those discussed, and 
there are no limitations on the use of the analysis. 
Although the data sets used in this analysis are listed currently as TBV, no impacts on the 
analysis are expected after the TBV status is revised. Five of the data sets were developed by 
USGS (DTN: GS970708315121.001, GS970708315121.002, GS991008315121.001, 
GS991008315121.002) and are expected to have full Q status following reverification. The four 
remaining data sets (DTN: GS000100001221.001, GS000200005121.001, 
GS000200005121.002, GS000200005121.003) have been designated Accepted Data per APSIII.
2Q. No impacts of TBVs on the analysis are expected.

 
78  
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8.3 SOURCE DATA, LISTED BY DATA TRACKING NUMBER 
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Future. 
GS000200005121.001. Earth Orbital Parameter Data for the Last 10 Million Years. 
GS000200005121.003. Radiometric Dating and d18O Data from Devils Hole, Nevada.