direct correlation of millennial scale changes in western north american vegetation and climate with changes in the california current system over the past 60 kyr terrestrial pollen and marine climate proxies from seven sediment cores taken on the continental margin of western north america between 32 and 43 n show systematically related short term changes superposed on milankovitch scale oscillations of the past 60 kyr during oxygen isotope stage 3 brief warming events in california and oregon appear correlative with interstadial events in waters offshore as do the rapid climate oscillations of the last glacial transition 14 10 ka estimated temperature depression of the coastal lowlands ranges from 10 c in southern california to 5 c in oregon during the last glacial the absence of long distance migration of pacific coastal plant assemblages concurs with marine evidence that southward movement of the polar front during the last glacial maximum was limited correlative changes in terrestrial and marine ecosystems imply that broad reorganizations of circulation in the northeast pacific ocean were synchronous with reorganizations of atmospheric circulation over western north america

late quaternary pollen record from the central california continental margin abstract a pollen record obtained from a deep sea core from the continental margin off central california contains evidence of the terrestrial floral adaptation to changing climatic conditions over the last ca 20 000 cal bp the pollen record is divided into three pollen zones two of which are late pleistocene in age glacial and transitional and the third is holocene interglacial the glacial pollen zone ca 20 000 17 000 cal bp is characterized by pinus and abies pollen reflecting environmental conditions during the last glacial maximum overlying this ca 17 000 11 600 cal bp is the transitional pollen zone containing a pollen assemblage indicative of a transitional climatic regime with species that reflect more arid environmental conditions pinus and artemisia decreasing in abundance and those reflecting moister conditions sequoia and alnus rising in abundance pediastrum and dinoflagellates are common and are attributable to increased nutrient rich coastal runoff the bolling allerod 295 256 cm ca 14 600 12 900 bp and younger dryas 256 243 cm ca 12 900 11 600 bp events occur within the transitional pollen zone as well the interglacial pollen zone ca 11 600 cal bp to present is characterized by decreasing pinus and increasing sequoia quercus and asteraceae reflecting changes in vegetation during the climatic warming of the holocene two brief dry periods are represented in this pollen zone one from 150 to 125 cm ca 8000 6400 cal bp and the other at 22 20 cm ca 800 700 cal bp they are correlated with the middle holocene dry period and the medieval climate anomaly respectively

late pleistocene and holocene paleoenvironments of the north pacific coast abstract unlike the north atlantic the north pacific ocean probably remained free of sea ice during the last glacial maximum lgm 22 000 to 17 000 bp following a eustatic low in sea level of ca 120 m at 19 000 bp a marine transgression had flooded the bering and chukchi shelves by 10 000 bp post glacial sea level history varied widely in other parts of the north pacific coastline according to the magnitude and timing of local tectonism and glacio isostatic rebound glaciers covered much of the continental shelf between the alaska peninsula and british columbia during the lgm maximum glacier extent during the lgm was out of phase between southern alaska and southern british columbia with northern glaciers reaching their outer limits earlier between 23 000 and 16 000 bp compared to 15 000 14 000 bp in the south glacier retreat was also time transgressive with glaciers retreating from the continental shelf of southern alaska before 16 000 bp but not until 14 000 13 000 bp in southwestern british columbia major climatic transitions occurred in the north pacific at 24 000 22 000 15 000 13 000 and 11 000 9000 bp rapid climate changes occurred within these intervals including a possible younger dryas episode an interval of climate warmer and drier than today occurred in the early holocene cooler and wetter conditions accompanied widespread neoglaciation beginning in some mountain ranges as early as the middle holocene but reaching full development after 3000 bp

climate and vegetation history from a 14 000 year peatland record kenai peninsula alaska abstract analysis of pollen spores macrofossils and lithology of an ams 14c dated core from a subarctic fen on the kenai peninsula alaska reveals changes in vegetation and climate beginning 14 200 cal yr bp betula expansion and contraction of herb tundra vegetation characterize the younger dryas on the kenai suggesting increased winter snowfall concurrent with cool sunny summers remarkable polypodiaceae fern abundance between 11 500 and 8500 cal yr bp implies a significant change in climate enhanced peat preservation and the occurrence of wet meadow species suggest high moisture from 11 500 to 10 700 cal yr bp in contrast to drier conditions in southeastern alaska this pattern may indicate an intensification and repositioning of the aleutian low al drier conditions on the kenai peninsula from 10 700 to 8500 cal yr bp may signify a weaker al but elevated fern abundance may have been sustained by high seasonality with substantial snowfall and enhanced glacial melt decreased insolation induced seasonality resulted in climatic cooling after 8500 cal yr bp with increased humidity from 8000 to 5000 cal yr bp a dry interval punctuated by volcanic activity occurred between 5000 and 3500 cal yr bp followed by cool moist climate coincident with neoglaciation tsuga mertensiana expanded after 1500 cal yr bp in response to the shift to cooler conditions

tephrochronology of late wisconsin deglaciation and holocene glacier fluctuations near glacier peak north cascade range washington abstract tephra layers near glacier peak in the north cascade range provide limiting dates for four periods of alpine glacier advance field relations suggest that late wisconsin alpine glaciers last advanced prior to the eruption of tephra layers from glacier peak about 11 250 yr b p late wisconsin deglaciation in the central north cascades was complete prior to the glacier peak tephra eruptions glaciers again expanded in the early holocene about 8400 8300 yr b p soil formed in alpine meadows during an episode of mild climate in the middle holocene prior to at least two intervals of glacier expansion an older episode between 5100 and 3400 yr b p and a younger episode within the last 1000 yr

latest pleistocene and holocene behaviour of franklin glacier mt waddington area british columbia coast mountains canada franklin glacier is an 18 km long valley glacier that originates in a broad icefield below the west face of mt waddington in the central british columbia coast mountains canada radiocarbon dated

postglacial vegetation and climate dynamics in the seymour belize inlet complex central coastal british columbia canada palynological evidence from tiny lake a pollen based study from tiny lake in the seymour belize inlet complex of central coastal british columbia canada permits an evaluation of the dynamic response of coastal temperate rainforests to postglacial climate change open pinus parklands grew at the site during the early lateglacial when the climate was cool and dry but more humid conditions in the later phases of the lateglacial permitted mesophytic conifers to colonise the region early holocene conditions were warmer than present and a successional mosaic oftsugaheterophylla andalnus occurred at tiny lake climate cooling and moistening at 8740 70 14 c a bp initiated the development of closed late successional t heterophylla cupressaceae forests which achieved modern character after 6860 50 14 c a bp when a temperate and very wet climate became established the onset of early holocene climate cooling and moistening at tiny lake may have preceded change at more southern locations including within the seymour belize inlet complex on a meso to synoptic scale this would suggest that an early holocene intensification of the aleutian low pressure system was an important influence on forest dynamics in the seymour belize inlet complex and that the study region was located near the southern extent of immediate influence of this semi permanent air mass copyright 2008 john wiley sons ltd

human responses to middle holocene climate change on california s channel islands abstract high resolution archaeological and paleoenvironmental records from california s channel islands provide a unique opportunity to examine potential relationships between climatically induced environmental changes and prehistoric human behavioral responses available climate records in western north america 7 3 8 ka indicate a severe dry interval between 6 3 and 4 8 ka embedded within a generally warm and dry middle holocene very dry conditions in western north america between 6 3 and 4 8 ka correlate with cold to moderate sea surface temperatures sst along the southern california coast evident in ocean drilling program odp core 893a b santa barbara basin an episode of inferred high marine productivity between 6 3 and 5 8 ka corresponds with the coldest estimated ssts of the middle holocene otherwise marked by warm low productivity marine conditions 7 5 3 8 ka the impact of this severe aridity on humans was different between the northern and southern channel islands apparently related to degree of island isolation size and productivity of islands relative to population fresh water availability and on going social relationships between island and continental populations northern channel islanders seem to have been largely unaffected by this severe arid phase in contrast cultural changes on the southern channel islands were likely influenced by the climatically induced environmental changes we suggest that productive marine conditions coupled with a dry terrestrial climate between 6 3 and 5 8 ka stimulated early village development and intensified fishing on the more remote southern islands contact with people on the adjacent southern california coast increased during this time with increased participation in a down the line trade network extending into the western great basin and central oregon genetic similarities between middle holocene burial populations on the southern channel islands and modern california uto aztecan populations suggest middle holocene movement of people at this time from southern california desert environs westward to the southern islands a migration perhaps stimulated by increased continental aridity

post glacial loess deposition in a montane environment south thompson river valley british columbia canada in the late wisconsinan the south thompson river valley british columbia was occupied by an ice dammed lake after the lake drained the exposed lacustrine silt became the source material for a holocene loess the purpose of this paper is to establish the stratigraphic depositional and geomorphic framework of loess occurring along the south thompson river valley immediately east of kamloops british columbia this montane environment of loess deposition was characterised by active slope and fluvial processes depositing sediments contemporaneously with the accumulation of loess the loess reaches an average of 4 m in thickness in the central part of the valley and thins towards the valley sides two tephras mount st helens y 3 4 ka and mount mazama 6 8 ka occur in the loess and are invaluable stratigraphic markers most of the loess was probably deposited between 8 2 ka and 3 4 ka a period coinciding with mid holocene increased summer temperatures and decreased precipitation in south central british columbia debris flows and small streams originating on the valley sides flowed out on to the loess depositing sand and gravel beds these deposits form a definite proximal distal relation across valley with the slope derived sediments decreasing and the loess increasing in thickness towards the centre of the valley the lactustrine silt particles were mobilised by diurnal mountain and valley gravity and canalised winds flowing within the south thompson valley an analysis of contemporary wind flow data was undertaken to provide a possible analogue for valley wind flows in the mid holocene

development history and carbon accumulation of a slope bog in oceanic british columbia canada palaeoecological techniques and radiocarbon datings were used to reconstruct the initiation and development of a sloping bog system near prince rupert british columbia canada peat initiation began around 12 000 cal bp possibly as a result of a cool wet climate prior to the insolation maximum a picea sitchensis tsuga heterophylla alnus minerotrophic wet fern forest occupied the study site from 9300 to 8300 cal bp between 8300 and 7500 cal bp cooler and wetter climatic conditions promoted increased organic matter accumulation and paludification by sphagnum species subsequent lateral expansion has been very slow in the later holocene paludification resulted in a shift to a scrubby less productive pinus contorta t heterophylla cupressaceae cyperaceae bog woodland around approximately 7500 3000 cal bp the modern cupressaceae pinus contorta t heterophylla ericaceae cyperaceae mire was well established by 2000 cal bp and a modern oceanic climate was predominant the initiation and development

postglacial wetland succession carbon accumulation and forest dynamics on the east coast of vancouver island british columbia canada peatland development and carbon accumulation on the pacific coast of canada have received little attention in paleoecological studies despite wetlands being common landscape features here we present a multi proxy paleoenvironmental study of an ombrotrophic bog in coastal british columbia following decreases in relative sea level the wetland was isolated from marine waters by 13 300 cal yr bp peat composition non pollen palynomorph and c and n analyses demonstrate terrestrialization from an oligotrophic lake to a marsh by 11 600 cal yr bp followed by development of a poor fen and then a drier ombrotrophic bog by 8700 cal yr bp maximum carbon accumulation occurred during the early holocene fen stage when seasonal differences in insolation were amplified this highlights the importance of seasonality in constraining peatland carbon sequestration by enhancing productivity during summer and reducing decomposition during winter pollen analysis shows that pinus contorta dominated regional forests by 14 000 cal yr bp warm and relatively dry summers in the early holocene allowed pseudotsuga menziesii to dominate lowland forests 11 200 7000 cal yr bp tsuga heterophylla and p menziesii formed coniferous forest in the mid and late holocene tephra matching the mid holocene glacier peak dusty creek assemblage provides evidence of its most northwesterly occurrence to date

late glacial to holocene changes in winds upwelling and seasonal production of the northern california current system abstract a core 120 km off the coast of southern oregon was examined for changes in lithology diatoms and pollen over the past 30 000 yr primary production during the late pleistocene was about half that of the holocene evidence from diatoms and pollen indicates that summer upwelling was much weaker implying an absence of strong northerly winds early pliocene diatoms found throughout the late pleistocene section were probably derived from diatomites east of the cascades and provide evidence for strong easterly winds over a dry continental interior the findings verify predictions of a climate model based on glacial maximum conditions there is no compelling evidence for a climatic reversal corresponding to the european younger dryas chron during the early holocene 9000 7000 yr b p there may have been years when winds were insufficiently strong to support upwelling so that warm stratified waters lay closer to the coast

recent and holocene climate change controls on vegetation and carbon accumulation in alaskan coastal muskegs abstract pollen spore macrofossil and carbon data from a peatland near cordova alaska reveal insights into the climate vegetation carbon interactions from the initiation of the holocene c the last 11 5 ka to the present 1 ka 1000 calibrated years before present where 0 1950 ce the holocene period is characterized by early deposition of gyttja in a pond environment with aquatics such as nuphar polysepalum and potamogeton and a significant regional presence of alnus crispa subsp sinuata carbon accumulation 50 g m 2 a was high for a short interval in the early holocene when sphagnum peat accumulated but was followed by a major decline to 13 g m 2 a from 7 to 3 7 ka when cyperaceae and ericads such as rhododendron formerly ledum groenlandicum expanded this shift to sedge growth is representative of many peatlands throughout the south central region of alaska and indicates a drier more evaporative environment with a large decline in carbon storage the subsequent return to sphagnum peat after 4 ka in the neoglacial represents a widespread shift to moister cooler conditions which favored a resurgence of ericads such as andromeda polifolia and increased carbon accumulation rate the sustained alnus expansion visible in the top 10 cm of the peat profile is correlative with glacial retreat and warming of the region in the last century and suggests this colonization will continue as temperature increases and ice melts

evidence for temporal fluctuations in marine radiocarbon reservoir ages in the santa barbara channel southern california abstract differences in the 14 c ages of closely associated marine shell and carbonized plant material from stratified archaeological deposits on san miguel island california suggest holocene 10 000 present fluctuations in marine 14 c reservoir ages these fluctuations coincide with 18 o and 13 c shifts measured in mytilus californianus shells from the same stratigraphic contexts and general atmospheric oceanic circulation models for the region based on these data we make three primary observations 1 significant changes appear to have occurred in the radiocarbon reservoir during the holocene 2 these fluctuations appear to correlate with regional oceanographic changes and 3 high resolution 14 c dating of marine shells may require different r values for different periods of time

high resolution climatic evolution of coastal northern california during the past 16 000 years holocene and latest pleistocene oceanographic conditions and the coastal climate of northern california have varied greatly based upon high resolution studies ca every 100 years of diatoms alkenones pollen caco 3 and total organic carbon at ocean drilling program odp site 1019 41 682 n 124 930 w 980 m water depth marine climate proxies alkenone sea surface temperatures ssts and caco 3 behaved remarkably like the greenland ice sheet project gisp 2 oxygen isotope record during the balling allerod younger dryas yd and early part of the holocene during the yd alkenone ssts decreased by 3 c below mean bolling allerod and holocene ssts the early holocene ca 11 6 to 8 2 ka was a time of generally warm conditions and moderate caco 3 content generally 4 the middle part of the holocene ca 8 2 to 3 2 ka was marked by alkenone ssts that were consistently 1 2 c cooler than either the earlier or later parts of the holocene by greatly reduced numbers of the gyre diatom pseudoeunotia doliolus 10 and by a permanent drop in caco 3 to 3 starting at ca 5 2 ka coastal redwood and alder began a steady rise arguing for increasing effective moisture and the development of the north coast temperate rain forest at ca 3 2 ka a permanent ca 1 c increase in alkenone sst and a threefold increase in p doliolus signaled a warming of fall and winter ssts intensified higher amplitude and more frequent cycles of pine pollen alternating with increased alder and redwood pollen are evidence that rapid changes in effective moisture and seasonal temperature enhanced el nino southern oscillation enso cycles have characterized the site 1019 record since about 3 5 ka

a deglacial and holocene record of climate variability in south central alaska from stable oxygen isotopes and plant macrofossils in peat we used stable oxygen isotopes derived from bulk peat d 18 otom in conjunction with plant macrofossils and previously published carbon accumulation records in a w14 500 cal yr bp peat core ht fen from the kenai lowlands in south central alaska to reconstruct the climate history of the area we find that patterns are broadly consistent with those from lacustrine records across the region and agree with the interpretation that major shifts in d 18 otom values indicate changes in strength and position of the aleutian low al a semi permanent low pressure cell that delivers winter moisture to the region we find decreased strength or a more westerly position of the al relatively higher d 18 otom values during the bolling allerod holocene thermal maximum htm and late holocene which also correspond to warmer climate regimes these intervals coincide with greater peat preservation and enhanced carbon c accumulation rates at the ht fen and with peatland expansion across alaska the htm in particular may have experienced greater summer precipitation as a result of an enhanced pacific subtropical high a pattern consistent with modern d 18 o values for summer precipitation the combined warm summer temperatures and greater summer precipitation helped promote the observed rapid peat accumulation a strengthened al relatively lower d 18 otom values is most evident during the younger dryas neoglaciation and the little ice age consistent with lower peat preservation and c accumulation at the ht fen suggesting less precipitation reaches the leeward side of the kenai mountains during periods of enhanced al strength the peatlands on the kenai peninsula thrive when the al is weak and the contribution of summer precipitation is higher highlighting the importance of precipitation seasonality in promoting peat accumulation this study demonstrates that d 18 otom values in peat can be applied

a holocene record of marine fish remains from the northeastern pacific abstract ocean drilling program leg 169s retrieved a complete holocene sequence from saanich inlet british columbia canada fish and diatom remains were extracted from sediments at site 1034 very small fish bones teeth and scales were ubiquitous except in the lowermost glaciomarine clays scales degraded with depth in the identifiable fraction pacific herring were the most abundant with pacific hake and cartilaginous fish yielding significant fractions fish remains appear just before 12 000 bp but greatest diversity does not occur until about 6500 bp a smoothed abundance curve highlights two periods of maximal abundance at about 1500 and 6500 bp abundances in the last 1000 years are lower than the rest of the record a correlation with abundances of seven phytoplankton taxa is significant diatoms explain about a third of the variance this study demonstrates the use of fish and diatoms from the same paleosedimentary matrix to examine millennia scale correlations between primary and tertiary production

late quaternary sea level change in southern beringia postglacial emergence of the western alaska peninsula abstract postglacial sea level trends have varied dramatically across the bering platform because of differences in coastal and shelf geologic settings emergent shorelines and basal peats along the western alaska peninsula indicate that relative sea level has fallen since regional deglaciation occurred ca 13 000 cal yr bp age elevation determinations on four shorelines 25 m 10 ka 16 m 9 6 6 ka 6 m 2 1 ka and 2 3 m 1 8 0 6 ka in the vicinity of cold and morzhovoi bays provide an estimate of the pace and timing of of sea level change since the last glacial maximum lgm 22 17 ka isostatic recovery and shoreline regression following the disintegration of continental and alpine ice has been interrupted by transgressive conditions at least twice since deglaciation changes in the balance between eustatic sea level rise and isostatic uplift resulted in the reactivation of marine scarps during the early to middle holocene but terrace cutting and a gap in the archaeological record about 2 1 ka suggest that sudden tectonic displacements also influence the record reconstructions of coastal paleogeography constrain the timing and distribution of regional archaeological settlement periods of shoreline erosion during stillstands or transgressions and the episodic reorganization of intertidal environments that accompanies tectonic displacements have conditioned site preservation potential and long term adaptive strategies

vegetation history of pleasant island southeastern alaska since 13 000 yr b p abstract a 13 000 year history of late quaternary vegetational and climatic change has been derived from lacustrine sediments from pleasant island in the glacier bay region of southeastern alaska early arrival of lodgepole pine and mountain hemlock indicated by the presence of pollen and conifer stomata suggests expansion from refugia in the alexander archipelago a short term climatic reversal possibly correlated with the european younger dryas is inferred from the expansion of tundra elements and deposition of inorganic sediments between 10 600 and 9900 14 c yr b p two peat cores from the lake catchment verify holocene vegetation changes and aid in the separation of biogenic from climatic forces affecting vegetation history differences in pollen representation among the three cores illustrate the variation among pollen collecting substrates as well as the spatial heterogeneity of peatland development and its dependence on local hydrology initial peat accumulation and soil paludification occasioned by increases in temperature and precipitation in the early holocene allowed western and mountain hemlock to replace sitka spruce 8500 8000 yr b p open muskeg became widespread about 7000 yr b p and allowed lodgepole pine to reinvade the region after a 2000 yr absence the extensive replacement of fen elements by bog taxa at 3400 yr b p suggests increased paludification due to changing hydrologic conditions its correlation with the upland expansion of tsuga heterophylla suggests the onset of a cooler wetter neoglacial climate in southeastern alaska

late glacial vegetation dynamics of the queen charlotte islands and adjacent continental shelf british columbia canada abstract ams radiocarbon dates and paleoecological analyses of sediments from the continental shelf between the queen charlotte islands and the british columbia mainland confirm that portions of the shelf were subaerially exposed and ice free between at least 14 330 and 12 860 14c years bp 17 370 14 570 cal years bp pollen analysis suggests that cyperaceae likely formed the dominant plant cover on the exposed shelf at dogfish bank and fossil pediastrum algae confirm the presence of freshwater pollen accumulation rates suggest low plant density on the exposed shelf although this is uncertain due to over and under representation of some pollen types in relation to vegetation abundance on the landscape paleoecological analyses of late glacial sediments at west side pond on the southern queen charlotte islands demonstrate succession from herb tundra dominated by cyperaceae at 13 750 14c years bp 16 830 cal years bp to dwarf shrub tundra with salix and empetrum nigrum after 13 500 14c years bp 16 400 cal years bp pteridophytes increased in abundance during the transition to pinus contorta woodland ca 13 000 14c years bp 15 600 cal years bp fossil conifer stomata suggest that p contorta grew locally as early as 13 040 305 14c years bp alnus crispa was co dominant by 11 500 14c years bp 13 500 cal years bp and picea sitchensis or its hybrids were present as early as 11 400 14c years bp 13 400 cal years bp in the south moresby area

late holocene fluctuations of the bear river glacier northern coast ranges of british columbia canada during holocene advances of the bear river glacier in northwestern british columbia ice pushed against a bedrock slope on the north side of bear river pass as it was being diverted eastward and westward along the pass the result is a series of till sheets plastered against the rock slope and separated by wood mats this sequence of tills provides an unusually detailed record of early neoglacial history and shows that neoglacial expansion in the northern coast mountains began earlier than previously known moraines show the extent of little ice age expansion and documents related to the long mining history of the area provide records of post lia recession the oldest deposits in the area are a small lateral moraine outside of a prominent lia moraine and a till in the pass older than c 3500 14c yr bp the small moraine is undated it may be equivalent to the latest pleistocene crowfoot advance which produced similar moraines in the southern coast mountains and eastern cordillera wood mats in the pa

regional significance of an early holocene moraine in enchantment lakes basin north cascade range washington abstract the upper enchantment lakes basin in the north cascade range of washington displays two moraine belts each recording an episode of glacier advance after the end of the last glaciation the inner belt the brynhild 0 1 to 0 5 km beyond existing glaciers postdates mount st helens wn tephra 450 yr old which lies only beyond the moraines the morainal surface is only slightly weathered is almost barren of lichens and is devoid of soil evidence suggesting that the brynhild moraines are no more than a century old the outer moraine the brisingamen 0 3 to 0 7 km beyond existing glaciers is weathered and is covered with large lichens on and behind the brisingamen moraine the mazama ash 6900 yr old is present beneath the mount st helens yn and wn tephras despite more than 7 millennia of weathering the rock surface behind the brisingamen moraine is measurably less weathered than the surface beyond which was last glaciated during the rat creek advance about 13 000 yr ago the age of the brisingamen moraine therefore is probably early holocene the brisingamen moraine evidently correlates with moraines near glacier peak near mount rainier in northeastern and central oregon in the southern canadian rockies and in the northern u s rocky mountains these regional effects suggest that a climatic episode of cooling or increased snowfall affected the entire region some time during the early holocene

lag of the fraser glacial maximum in the pacific northwest pollen and macrofossil evidence from western fraser lowland british columbia pollen and macrofossil evidence from two sites in northwestern fraser lowland reveals that abies lasiocarpa picea cf engelmannii forest and parkland grew there about 18 000 years ago under cold humid continental conditions taxus brevifolia was also a significant constituent of this forest this plant assemblage resembles the essf biogeoclimatic zone of subalpine elevations in the northern interior of british columbia 900 2250 m climate was probably cold with low to moderate rainfall and characterized by long cold wet winters and very short probably dry frost free summers mean annual temperature was depressed about 8 c and the tree line was probably 1200 1500 m lower than today fraser lowland was probably removed from pacific oceanic influence because the land sea interface was located on the continental shelf to the west of vancouver island and washington about the time of the last global glacial maximum global depression of sea level and quadra sand aggradation in the pacific northwest lo

holocene soil geomorphic surfaces influence the role of salmon derived nutrients in the coastal temperate rainforest of southeast alaska abstract the influence of salmon derived nutrients sdn is widely accepted as a potential factor in the maintenance of aquatic and terrestrial productivity in north american coastal rainforests holocene alluvial landforms are intimately connected with the return of anadromous salmon but the influence of the soils that occupy these landforms and support this important terrestrial aquatic ecological coupling have not been examined in sdn studies we used paleo ecologic information soil resource inventories and measurements of soil morphology to construct a soil geomorphic model for alluvial landforms along salmon spawning channels on prince of wales island southeast alaska usa post glacial sea level rise crustal uplift and subsidence combined with holocene sediment deposition have formed alluvial terraces and floodplains along rivers on prince of wales island these alluvial landforms have soils that are mapped as entisols tonowek soil series and spodosols tuxekan soil series we propose a soil geomorphic model where the spodosols located on terraces are estimated to derive from sediments deposited after the stabilization of landscape approximately 8 kybp to 6 kybp the stability of these soils is reflected through mature soil development with organic matter accumulation and podzolization our model identifies entisols on floodplains developed from alluvial deposition in the latter holocene that have soil morphologic features consistent with recent deposition and limited soil development we used this soil geomorphic model to test the hypothesis that the terrestrial end member value commonly used to quantify nitrogen n loading on soils through stable isotope analysis differs by soil type and found that the two soil types had significantly different n isotopic 15n values more consistent with soil development than sdn loading the use of a soil geomorphic model provides a means to stratify alluvial landforms and constrain the natural variability encountered in studies of riparian nutrient cycles associated with the feedbacks between sdn and terrestrial ecosystems to improve estimates of the fate of sdn in soils and vegetation

impacts of climate and vegetation change on carbon accumulation in a south central alaskan peatland assessed with novel organic geochemical techniques to constrain the effect of climate and peatland type on carbon accumulation we reconstructed these parameters from a holocene length core of a sphagnum dominated peatland near cordova ak usa we determined peat type using a combination of peat texture and density macrofossils distributions of leaf wax biomarkers and soil ph reconstructions based on distributions of branched glycerol dialkyl glycerol tetraether lipids brgdgts we produced an independent record of hydroclimate and temperature change using hydrogen isotope ratios of leaf wax biomarkers and distributions of brgdgts carbon accumulation rates were constrained with 14 ams 14c dates from identified macrofossils and ash free bulk density in the early holocene the site was a shallow pond with evidence for emergent macrophytes sphagnum and algae growing in a warm moist climate at 9 2 kyr 1 kyr 1000 cal yr bp the site became a sphagnum dominated bog under mid holocene warm evaporative climate conditions the site became sedge dominated as climate cooled and effective precipitation increased sphagnum was able to gain dominance abruptly at 3 5 kyr large changes in the vegetation assemblage and hydrology and climate are contemporaneous with significant changes in the rate of carbon accumulation carbon accumulated most rapidly when sphagnum dominated and effective moisture was high and most slowly when sedges were dominant and conditions were warmer and drier estimates of future climate change indicate warmer more evaporative conditions that in the past favored a sedge dominated environment suggesting that this peatland and those similar can contribute to a positive feedback to warming by transitioning to less efficient carbon sinks

polar perspective of late quaternary climates in the southern hemisphere abstract late quaternary paleoecological and glacial evidence from the higher latitudes of the southern hemisphere implies overall uniformity of large scale glacial and interglacial climatic fluctuations for the past 40 000 yr climate of the last glacial maximum variously dated between 30 000 and 11 000 yr b p was relatively cold and dry compared with the warmer more humid climate of the holocene and the interstade preceding the last glacial maximum conditions were apparently coldest during millennia centered around 20 000 yr b p and warmest in the early holocene recorded small scale fluctuations frequently variable for any given time interval are less consistent a cold late glacial episode estimated as occurring between ca 13 000 and 11 000 yr b p in antarctica possibly was coeval with the younger dryas stade in northwestern europe and may be correlative with a climatic episode in southern south america and perhaps in new zealand and south georgia however there is no evidence for the event in tasmania general atmospheric circulation models for the polar latitudes at the time of the last glacial maximum show an intensification of the southern westerlies apparently a result of the expansion of ice cover in antarctica and of sea ice in the southern ocean

a 14 000 year vegetation history of a hypermaritime island on the outer pacific coast of canada based on fossil pollen spores and conifer stomata abstract pollen and conifer stomata analyses of lake sediments from hippa island on the north coast of british columbia were used to reconstruct the vegetation history of this small hypermaritime island between 14 000 and 13 230 cal yr bp the island supported diverse herb shrub communities dominated by cyperaceae artemisia and salix pinus contorta and picea sitchensis stomata indicate that these conifers were present among the herb shrub communities likely as scattered individuals transition to open p contorta woodland by 13 000 cal yr bp was followed by increases in alnus viridis alnus rubra and p sitchensis after 12 000 cal yr bp pinus dominated communities were replaced by dense p sitchensis and tsuga heterophylla forest with lysichiton americanus and fern understory thuja plicata stomata indicate that this species was present by 8700 cal yr bp but the pollen record suggests that its populations did not expand to dominate regional rainforests along with tsuga and picea until after 6600 cal yr bp conifer stomata indicate that species may be locally present for hundreds to thousands of years before pollen exceed thresholds routinely used to infer local species arrival when combined pollen and conifer stomata can provide a more accurate record of paleovegetation than either when used alone

late pleistocene bison antiquus from orcas island washington and the biogeographic importance of an early postglacial land mammal dispersal corridor from the mainland to vancouver island abstract a bison antiquus cranium and partial skeleton from ayer pond wetland on orcas island san juan islands washington date to 11 760 70 14 c yr bp they lay in lacustrine sediments below peat unconformably above emergent everson glaciomarine drift 12 000 14 c yr bp several bison finds in similar contexts on orcas and vancouver islands dating between 11 750 and 10 800 14 c yr bp indicate an early postglacial land mammal dispersal corridor with reduced water barriers between mainland and islands new bison dates and published shell dates allow estimation of early postglacial relative sea level trends for the san juans with a drop below modern datum 12 000 14 c yr bp and assist in evaluation of marine reservoir corrections emergence by 60 m is suggested by data from nearby areas a tundra like or meadow community and succeeding open pine parkland before 11 000 14 c yr bp supported bison but horn core reduction suggests suboptimal forage or restricted habitat expanding mixed conifer forests after 11 000 14 c yr bp contributed to bison extirpation dispersing ungulates such as bison must have influenced island vegetation establishment and early succession possible evidence for butchering by early coastal people adds significance to the ayer pond discovery given its pre clovis age

holocene development of boreal forests and fire regimes on the kenai lowlands of alaska several studies have noted a relationship between vegetation type and fire frequency yet despite the importance of ecosystem processes such as fire the long term relationships between disturbance climate and vegetation type are incompletely understood we analysed pollen plant macrofossils and sedimentary charcoal from three lakes within the kenai lowlands to determine postglacial relationships between disturbance climate and vegetation for the boreal forest of southwest alaska an herb tundra was established in the lowlands following deglaciation by 13 000 cal bp salix alnus and probably betula kenaica expanded in the area after 10 700 cal bp followed by picea glauca by 8500 cal bp picea mariana became established by 4600 cal bp the early holocene was probably the driest time during the postglacial as determined by aquatic plant macrofossils and climate models lake levels reached near modern conditions by at least 8000 cal bp mean fire intervals mfi were longest during the shrubherb tundra phase 1389 65 yr decreased after expansion of b kenaica salix and populus 779 49 yr and picea glauca 819 41 yr and increased again with the arrival of p mariana 1309 66 yr unlike previous studies our data demonstrate the highest fire frequencies during the early to mid holocene and less frequent fire during the late holocene when p mariana forests dominated the lowlands early holocene forests of p glauca and b kenaica existed in summers that were longer and drier than today while the increasingly wetter and cooler climates of the late holocene probably hindered forest fire around paradox lake perhaps because of less frequent summer drought

ecosystem development in the girdwood area south central alaska following late wisconsin glaciation pollen analysis of two cores with discontinuous records from a peat bog near girdwood in south central alaska provides the basis for reconstructing the first radiocarbon dated outline of postglac

holocene climate changes in eastern beringia nw north america a systematic review of multi proxy evidence abstract reconstructing climates of the past relies on a variety of evidence from a large number of sites to capture the varied features of climate and the spatial heterogeneity of climate change this review summarizes available information from diverse holocene paleoenvironmental records across eastern beringia alaska westernmost canada and adjacent seas and it quantifies the primary trends of temperature and moisture sensitive records based in part on midges pollen and biogeochemical indicators compiled in the recently published arctic holocene database and updated here to v2 1 the composite time series from these proxy records are compared with new summaries of mountain glacier and lake level fluctuations terrestrial water isotope records sea ice and sea surface temperature analyses and peatland and thaw lake initiation frequencies to clarify multi centennial to millennial scale trends in holocene climate change to focus the synthesis the paleo data are used to frame specific questions that can be addressed with simulations by earth system models to investigate the causes and dynamics of past and future climate change this systematic review shows that during the early holocene 11 7 8 2 ka 1 ka 1000 cal yr bp rather than a prominent thermal maximum as suggested previously temperatures were highly variable at times both higher and lower than present approximate mid 20th century average with no clear spatial pattern composited pollen midge and other proxy records average out the variability and show the overall lowest summer and mean annual temperatures across the study region during the earliest holocene followed by warming over the early holocene the sparse data available on early holocene glaciation show that glaciers in southern alaska were as extensive then as they were during the late holocene early holocene lake levels were low in interior alaska but moisture indicators show pronounced differences across the region the highest frequency of both peatland and thaw lake initiation ages also occurred during the early holocene during the middle holocene 8 2 4 2 ka glaciers retreated as the regional average temperature increased to a maximum between 7 and 5 ka as reflected in most proxy types following the middle holocene thermal maximum temperatures decreased starting between 4 and 3 ka signaling the onset of neoglacial cooling glaciers in the brooks and alaska ranges advanced to their maximum holocene extent as lakes generally rose to modern levels temperature differences for averaged 500 year time steps typically ranged by 1 2 c for individual records in the arctic holocene database with a transition to a cooler late holocene that was neither abrupt nor spatially coherent the longest and highest resolution terrestrial water isotope records previously interpreted to represent changes in the aleutian low pressure system around this time are here shown to be largely contradictory furthermore there are too few records with sufficient resolution to identify sub centennial scale climate anomalies such as the 8 2 ka event the review concludes by suggesting some priorities for future paleoclimate research in the region

timing and climatic controls over neoglacial expansion in the northern coast mountains british columbia canada holocene sedimentary records from two lakes in white pass british columbia show that the onset of neoglacial sedimentation began c 2 ka cal bp prior to this time the lakes accumulated organicrich sediments with properties and sedimentation rates similar to adjacent lakes that have not had glacial influences during the holocene neoglaciation at white pass was coincident with the increased delivery of exotic tsuga heterophylla western hemlock pollen these results together with regional indications for increased delivery of hemlock pollen at 2 ka bp by a deepened low pressure in the northeastern pacific ocean suggest that increased moisture was important for the expansion of glaciers in the region in addition to longer term late holocene cooling

holocene glacier fluctuations in alaska abstract this review summarizes forefield and lacustrine records of glacier fluctuations in alaska during the holocene following retreat from latest pleistocene advances valley glaciers with land based termini were in retracted positions during the early to middle holocene neoglaciation began in some areas by 4 0 ka and major advances were underway by 3 0 ka with perhaps two distinct early neoglacial expansions centered respectively on 3 3 2 9 and 2 2 2 0 ka tree ring cross dates of glacially killed trees at two termini in southern alaska show a major advance in the ad 550s 720s the subsequent little ice age lia expansion was underway in the ad 1180s 1320s and culminated with two advance phases respectively in the 1540s 1710s and in the 1810s 1880s the lia advance was the largest holocene expansion in southern alaska although older late holocene moraines are preserved on many forefields in northern and interior alaska tidewater glaciers around the rim of the gulf of alaska have made major advances throughout the holocene expansions were often asynchronous with neighboring termini and spanned both warm and cool intervals suggesting that non climatic factors were important in forcing these advances however climatic warming appears to have initiated most rapid iceberg calving retreats large glaciers terminating on the forelands around the gulf of alaska may have had tidewater termini early in the holocene but have progressively become isolated from the adjacent ocean by the accumulation and subaerial exposure of their own sediments

holocene precipitation in the coastal temperate rainforest complex of southern british columbia canada abstract pollen data from 69 surface samples from vancouver island canada were used to develop a ratio index of precipitation douglas fir western hemlock index dwhi dwhi ratios were combined with interpolated estimates of mean annual precipitation to develop pollen based precipitation transfer functions the optimal regression model with a predictive range of 960 2600 mm was applied to 10 holocene lake sediment records distributed across a 150 km long coastal inland precipitation gradient predicted precipitation was spatially modelled in a geographic information system to examine the spatio temporal history of precipitation from this representative portion of the coastal temperate rainforest ctr complex of western north america the reconstructions show widespread early holocene dry conditions coupled with a steep east west precipitation gradient thereafter the modern precipitation gradient established 7000 years ago illustrating that the ctr complex has experienced marked short distance east west changes in precipitation in the past changes in the abundance of arboreal and non arboreal vegetation as well as fire disturbance are often concomitant with changes in holocene precipitation given the precipitation and vegetation history of the region conservation initiatives should focus on the moist outer coastal zone since it appears to have the greatest amount of resilience to perturbations in precipitation whereas monitoring programs for signs of climate change should be initiated in central and eastern areas as they appear sensitive to changes in the moisture regime

early and late holocene glacial fluctuations and tephrostratigraphy cabin lake alaska marked changes in sediment types deposited in cabin lake near cordova alaska represent environmental shifts during the early and late holocene including fluctuations in the terminal position of sheridan glacier cabin lake is situated to receive meltwater during periods when the outwash plain of the advancing sheridan glacier had aggraded a brief early holocene advance from 11 2 to 11 0 cal ka is represented by glacial rock flour near the base of the sediment core non glacial lake conditions were restored for about 1000 years before the water level in cabin lake lowered and the core site became a fen the fen indicates drier than present conditions leading up to the holocene thermal maximum an unconformity spanning 5400 years during the mid holocene is overlain by peat until 1110 ce when meltwater from sheridan glacier returned to the basin three intervals of an advanced sheridan glacier are recorded in the cabin lake sediments during the late holocene 1110 1180 1260 1540 and 1610 1780 ce the sedimentary sequence also contains the first five reported tephra deposits from the copper river delta region and their geochemical signatures suggest that the sources are the cook inlet volcanoes redoubt augustine and crater peak and possibly mt churchill in the wrangell volcanic field copyright 2013 john wiley sons ltd

multi millennial streamflow dynamics in two forested watersheds on vancouver island canada abstract holocene streamflow was reconstructed for two rivers on vancouver island british columbia canada in 500 yr intervals the san juan river watershed is located on the wetter western side of the island whereas the koksilah river watershed is positioned on the drier eastern side both watersheds are forested to reconstruct streamflow temporal changes in precipitation estimated using a pollen based transfer function and evapotranspiration were established for each watershed and integrated into a water balance model calibrated using modern data while seasonal streamflow variability was maintained throughout the holocene with greater flow in the winter relative to the summer the amount of discharge has changed markedly through time lowest simulated flow occurred in the earliest holocene with low flow conditions beginning earlier in the year and extending later into the fall such conditions may have inhibited salmon from using many of the smaller rivers in the region streamflow steadily increased throughout the early holocene so that by ca 6500 cal yr before present near modern flow regimes were established as climate changes in the future the san juan and koksilah watersheds are expected to remain as pluvial hydroclimatic regimes though with an extended season of low flow similar to conditions during the early holocene

semi determinate hydraulic geometry of river channels south island new zealand data to describe the morphologic hydrologic and sedimentologic characteristics of 72 south island new zealand rivers were collected and analysed nearly 70 per cent of variation in channel morphology is accounted for by differences in cross sectional area slope and cross section shape only 53 per cent of the morphologic variability could be statistically explained by the hydrologic and sediment variables used the level of explanation varied for different morphologic variables nearly 90 per cent of the variability in cross sectional area could be explained but aspect ratio maximum depth divided by hydraulic radius was completely independent apart from the inadequacy of the measured variables as indices of the true underlying controlling factors and the imperfect measurement and sampling procedures the low level of explanation is probably due to the influence of factors such as floodplain vegetation high quasi random variability in bark sediment character boundary effects imposed by bedrock bluffs and the precise sequence of flood events none of which are easily quantified in addition observations indicate that there is a large random variation in channel form which cannot be related to any factor an attempt to relate channel morphology to flow variability using simple indices of the latter was unsuccessful

early holocene glacier advance in the north cascade range washington moraines and glacial drift of the white chuck advance were deposited in early holocene time in cirques near glacier peak washington these sediments overlie glacier peak tephra including layers g n f c m t and b which were erupted between about 12 500 and 11 250 yr b p white chuck drift is overlain by mazama tephra layer o deposited about 6 700 yr b p charcoal collected from till deposited during the white chuck advance is about 8 300 to 8 400 radiocarbon years old indicating that the glacial advance that deposited the till occurred about this time and that a previously unrecognized period of cooling and or increased precipitation of sufficient intensity to produce glacial advances comparable to or greater than those of the recent little ice age occurred in early holocene time in the north cascade range other pre altithermal moraines from the cascades the rocky mountains laurentide canada and baffin island may have been produced during this cool period

regional atmospheric circulation change in the north pacific during the holocene inferred from lacustrine carbonate oxygen isotopes yukon territory canada analyses of sediment cores from jellybean lake a small evaporation insensitive groundwater fed lake provide a record of changes in north pacific atmospheric circulation for the last 7500 yr at 5 to 30 yr resolution isotope hydrology data from the southern yukon indicate that the oxygen isotope composition of water from jellybean lake reflects the composition of mean annual precipitation 18op recent changes in the 18o of jellybean sedimentary calcite 18oca correspond to changes in the north pacific index npi a measure of the intensity and position of the aleutian low al pressure system this suggests that 18op variability was related to the degree of fractionation during moisture transport from the gulf of alaska across the st elias mountains and that holocene shifts were controlled by the intensity and position of the al following this model between 7500 and 4500 cal yr b p long term trends suggest a predominantly weaker and or westward al between 4500 and 3000 cal yr b p the al shifted eastward or intensified before shifting westward or weakening between 3000 and 2000 cal yr b p rapid shifts eastward and or intensification occurred 1200 and 300 cal yr b p holocene changes in north pacific atmospheric circulation inferred from jellybean lake oxygen isotopes correspond with late holocene glacial advances in the st elias mountains changes in north pacific salmon abundance and shifts in atmospheric circulation over the beaufort sea

humptulips revisited a revised interpretation of quaternary vegetation and climate of western washington usa abstract new pollen data from a 770 cm core of a mire at humptulips on the southwestern olympic peninsula 47 17 00 n 123 54 40 w and from a nearby deposit regarded as interglacial in age on the west fork of the humptulips river provide evidence for a reinterpretation of previous accounts of the quaternary vegetation and climate using a new age model the highly variable record at humptulips is here correlated with marine oxygen isotope stages ois 1 5a vegetation during ois 5a was pine dominated mixed woodland and tundra in ois 4 3 and 2 oscillations in pollen assemblages imply repeated intervals of mountain hemlock parkland and tundra pine as an indicator of openness is also abundant in these stages interstadial fluctuations in ois 3 reflect episodes of lowland western hemlock communities the earliest of the episodes is of infinite radiocarbon age and the latest dates to approximately 30 000 14 c yr b p parkland in ois 2 occurring after 24 600 until at least 18 440 14 c yr b p was replaced by transitional pine alder in ois 1 holocene which unlike any of the earlier stages conveys the development of modern lowland forest dominated by western hemlock pollen assemblages over the length of record imply that temperature and humidity at no time were as high as at present only in ois 3 do conditions approach those occurring in ois 1 during ois 2 3 and 4 when tree line apparently stood at the location of the site climate was colder and drier temperatures were depressed an estimated 5 c with precipitation close to 1000 mm compared with 2000 3000 mm at present atmospheric circulation during ois 2 appears to have been much controlled by the location of the laurentide ice sheet in the continental interior whereas under the current climatic regime beginning in the early holocene westerly air flow has dominated regulated by interplay between the north pacific high in summer and the wintertime aleutian low

monsoon climate of the early holocene climate experiment with the earth s orbital parameters for 9000 years ago values for the precession and obliquity of the earth 9000 years ago indicate that the global average solar radiation for july 9000 years ago was 7 percent greater than at present when the estimated solar radiation values are used in a low resulation climate model the model simulates an intensified continent scale monsoon circulation this result agrees with paleoclimatic evidence from africa arabia and india that monsoon rains were stronger between 10 000 and 5000 years ago than they are today

the practical application of 2d inversion to marine controlled source electromagnetic data an algorithm is presented for the inversion of marine controlled source electromagnetic csem data that uses a 2d finite difference fd forward driver this code is demonstrated by inverting a csem data set collected at hydrate ridge oregon consisting of 25 seafloor sites recording a 5 hz transmission frequency the sites are located across a bathymetric high with variations in water depth of 300 m along the 16 km profile to model this complex seafloor bathymetry accurately the fd grid was designed by careful benchmarking using a different 2d finite element fe forward code a comparison of the fe and fd forward model solutions verifies that no features in the inversion are due to inaccuracies of the fd grid the inversion includes the local seawater conductivity depth profile as recorded by the transmitter s conductivity temperature depth gauge because seawater conductivity is known to have a significant effect on the csem responses an apparent resistivity pseudosection of the csem data resemb

holocene glaciation of alaska and adjoining yukon territory canada abstract holocene glacial fluctuations between arctic central interior and southern maritime alaska are broadly synchronous this synchrony is evident from a review of work in 11 study areas with varying numbers of glaciers 3 100 glacier types subpolar cirque temperate valley tidewater surging and dating methodologies the pattern is temporally and spatially consistent with vegetation data and generally with climatic deteriorations culminating in the little ice age early holocene glacial advances are confirmed for 7 6 5 8 lichen ka bp at 4 of 97 glaciers in the brooks range advances also occurred by 5 85 and 5 7 ka bp at separate glacier tongues in the northern alaska range at least by 6 5 ka bp in lituya bay and possibly also in the malaspina and aleutian islands areas a sharp increase in glacier activity began by 4 4 ka bp in the arctic and glacier bay areas and by about 3 ka bp major glacier advances probably were initiated or well underway throughout alaska during holocene glacial maxima ice filled glacier and lituya bays as well as fjords of prince william sound and massive moraines buried forests in the northeastern st elias mountains area minor recession is recorded directly or implied in most of alaska about 2 ka bp or locally through the following millennium subsequently distinct but locally weak advances occurred by about 1 2 ka bp in most areas again followed by intervals of glacier recession most pervasive and ubiquitous were the little ice age advances initiated about 700 bp these generally culminated in two major advances between about 400 and 50 bp in the arctic those of a d 1600 dominated those of the late 1800s in the gulf of alaska those of the middle 1700s or late 1800s dominated large scale asynchronous advances and retreats of calving tidewater glaciers have been recorded during the twentieth century but most such movements are only indirectly related to climate

evidence from north west canada for an early holocene milankovitch thermal maximum according to the milankovitch theory of global climatic change maximum summer solar radiation at high latitudes of the northern hemisphere occurred at 10 000 yr bp refs 1 2 in particular it predicts summer solstice radiation greater by 9 10 preliminary climate simulation experiments with these increased values of radiation confirm that high latitude land surfaces received maximal insolation at 10 000 yr refs 3 4 paradoxically however the large volume of fossil pollen and other evidence from north america indicates a maximum of holocene warmth at 7 000 6 000 yr ref 5 and a recent review of the evidence from new england suggests that the warming began at 9 000 and ended at 5 000 yr but also stresses the difficulties of interpretation in terms of climate change6 we summarize here data from sites in the north west corner of mainland canada fig 1 that directly support the milankovitch hypothesis

a multi proxy peat study of holocene vegetation history bog development and carbon accumulation on northern vancouver island pacific coast of canada we present a multi proxy paleoenvironmental study on a 10 400 cal yr peat sequence from an ombrotrophic bog in coastal british columbia canada pollen non pollen palynomorph plant macrofossil and physicochemical analyses bulk density c n 13c and 15n isotopes were used to document changes in vegetation bog development and carbon and nitrogen accumulation pollen assemblages indicate that regional vegetation in the warm relatively dry early holocene was mixed coniferous forest with scattered pseudotsuga menziesii herbaceous peat with a c n of 28 combined with nuphar microfossils and relatively high n suggests the presence of a herb dominated peatland with standing water and or bog pools carbon and nitrogen accumulation were at their highest during this early holocene period at mean rates of 30 6 and 1 2 g m2 cal yr respectively by 8000 cal yr bp and under a cooler wetter climate northern vancouver island supported tsuga heterophylla rainforest similar to today decreasing relat

postglacial vegetation history of mitkof island alexander archipelago southeastern alaska abstract an ams radiocarbon dated pollen record from a peat deposit on mitkof island southeastern alaska provides a vegetation history spanning 12 900 cal yr bp to the present late wisconsin glaciers covered the entire island deglaciation occurred 15 400 cal yr bp the earliest known vegetation to develop on the island 12 900 cal yr bp was pine woodland pinus contorta with alder alnus sedges cyperaceae and ferns polypodiaceae type by 12 240 cal yr bp sitka spruce picea sitchensis began to colonize the island while pine woodland declined by 11 200 cal yr bp mountain hemlock tsuga mertensiana began to spread across the island sitka spruce mountain hemlock forests dominated the lowland landscapes of the island until 10 180 cal yr bp when western hemlock tsuga heterophylla began to colonize and soon became the dominant tree species rising percentages of pine sedge and sphagnum after 7100 cal yr bp may reflect an expansion of peat bog habitats as regional climate began to shift to cooler wetter conditions a decline in alders at that time suggests that coastal forests had spread into the island s uplands replacing large areas of alder thickets cedars chamaecyparis nootkatensis thuja plicata appeared on mitkof island during the late holocene

stratigraphy of the colorado creek mammoth locality alaska abstract the colorado creek mammoth locality in west central alaska contains the remains of two mammoths that were scavenged by carnivores sedimentologic interpretations of the reworked eolian deposits surrounding the bones supplemented by 10 radiocarbon dates indicate that the lower and upper mammoths died and were buried within separate but superimposed thaw gullies about 23 000 and 16 000 yr ago respectively from our results we propose a polycyclic taphonomic model for thaw gullies governed largely by slope aspect rather than regional climate and in which mixing between faunal horizons is more likely than not variations in the rate of silt influx and the position of the permafrost table provide a paleoclimatic proxy record that can be correlated to other records in eastern beringia

holocene thermal maximum in the western arctic 0 180 w the spatio temporal pattern of peak holocene warmth holocene thermal maximum htm is traced over 140 sites across the western hemisphere of the arctic 0 180 w north of 60 n paleoclimate inferences based on a wide variety of proxy indicators provide clear evidence for warmer than present conditions at 120 of these sites at the 16 terrestrial sites where quantitative estimates have been obtained local htm temperatures primarily summer estimates were on average 1 6 0 8 c higher than present approximate average of the 20th century but the warming was time transgressive across the western arctic as the precession driven summer insolation anomaly peaked 12 10 ka thousands of calendar years ago warming was concentrated in northwest north america while cool conditions lingered in the northeast alaska and northwest canada experienced the htm between ca 11 and 9 ka about 4000 yr prior to the htm in northeast canada the delayed warming in quebec and labrador was linked to the residual laurentide ice sheet which chilled the region through its impact on surface energy balance and ocean circulation the lingering ice also attests to the inherent asymmetry of atmospheric and oceanic circulation that predisposes the region to glaciation and modulates the pattern of climatic change the spatial asymmetry of warming during the htm resembles the pattern of warming observed in the arctic over the last several decades although the two warmings are described at different temporal scales and the htm was additionally affected by the residual laurentide ice the similarities suggest there might be a preferred mode of variability in the atmospheric circulation that generates a recurrent pattern of warming under positive radiative forcing unlike the htm however future warming will not be counterbalanced by the cooling effect of a residual north american ice sheet

holocene glacier activity in the british columbia coast mountains canada abstract the coast mountains flank the pacific ocean in western british columbia canada subdivided into the southern pacific ranges central kitimat ranges and northern boundary ranges the majority of large glaciers and icefields are located in the boundary and pacific ranges prior descriptions of the holocene glacial history of this region indicate the holocene was characterized by repeated episodes of ice expansion and retreat recent site specific investigations augment our understanding of the regional character and duration of these events in this paper previously reported and new radiocarbon evidence is integrated to provide an updated regional assessment the earliest evidence of glacier expansion in the coast mountains comes from the boundary ranges at 8 9 and 7 8 ka and in the pacific ranges at 8 5 8 2 ka with the latter advance corresponding to an interval of rapid global climate deterioration although generally warm and dry climates from 7 3 to 5 3 ka likely limited the size of glaciers in the region there is radiocarbon evidence for advances over the interval from 7 3 to 6 0 and at 5 4 5 3 ka in the pacific ranges following these advances glaciers in the pacific ranges expanded down valley at 4 8 4 6 4 4 4 0 3 5 2 6 1 4 1 2 and 0 8 0 4 ka while glaciers in boundary ranges were advancing at 4 1 4 0 3 7 3 4 3 1 2 8 2 3 1 7 1 1 and 0 8 0 4 ka after 0 4 ka it appears that most glaciers in the coast mountains continued to expand to attain their maximum holocene extents by the early 18th to late 19th centuries this enhanced record of holocene glacier activity highlights the temporal synchrony in the coast mountains individual expansion events in the mid to late holocene broadly correspond to intervals of regional glacier activity reported in the canadian rocky mountains in alaska and on high elevation volcanic peaks in washington state

late holocene moisture balance variability in the southwest yukon territory canada abstract analyses of sediment cores from marcella lake a small hydrologically closed lake in the semi arid southwest yukon provides effective moisture information for the last 4500 years at century scale resolution water chemistry and oxygen isotope analyses from lakes and precipitation in the region indicate that marcella lake is currently enriched in 18 o by summer evaporation past lake water values are inferred from oxygen isotope analyses of sedimentary endogenic carbonate in the form of algal charophyte stem encrustations a record of the 18 o composition of mean annual precipitation at jellybean lake a nearby evaporation insensitive system provides data of simultaneous 18 o variations related to decade to century scale shifts in aleutian low intensity position the difference between the two isotope records represents 18 o enrichment in marcella lake water caused by summer effective moisture conditions results indicate increased effective moisture between 3000 and 1200 cal bp and two marked shifts toward increased aridity at 1200 and between 300 and 200 cal bp these prominent late holocene changes in effective moisture occurred simultaneously with changes in aleutian low circulation patterns over the gulf of alaska indicated by jellybean lake the reconstructed climate patterns are consistent with the topographically controlled climatic heterogeneity observed in the coastal mountains and interior valleys of the region today

enhanced late holocene enso pdo expression along the margins of the eastern north pacific abstract pacific climate is known to have varied during the holocene but spatial patterns remain poorly defined this paper compiles terrestrial and marine proxy data from sites along the northeastern pacific margins and proposes that they indicate 1 suppressed enso conditions during the middle holocene between 8000 and 4000 cal bp with a north pacific that generally resembled a la nina like or more negative pdo phase and 2 a climate transition between 4200 and 3000 cal bp that appears to be the teleconnected expression to a more modern like enso pacific compared to modern day conditions the compiled data suggest that during the middle holocene the aleutian low was generally weaker during the winter and or located more to the west while the north pacific high was stronger during the summer and located more to the north coastal upwelling off california was more enhanced during the summer and fall but suppressed during the spring oregon and california sea surface temperatures ssts were cooler the santa barbara basin had an anomalous record suggesting warmer ssts late holocene records indicate a more variable el nino like and more positive pdo pacific the aleutian low became more intensified during the winter and or located more to the east the north pacific high became weaker and or displaced more to the south coastal upwelling off california intensified during the spring but decreased during the fall oregon and california ssts became warmer recording the shoreward migration of sub tropical gyre waters during the fall while spring upwelling cooler sst increased in the santa barbara basin the high resolution proxy records indicate enhanced enso and pdo variability after 4000 cal bp off southern california 3400 cal bp off northern california and by 2000 cal bp in southwestern yukon a progressively northward migration of the enso teleconnection during the late holocene is proposed

holocene fluctuations of a meromictic lake in southern british columbia abstract holocene deposits of mahoney lake a meromictic saline lake located in a closed basin in the semi arid okanagan valley contain evidence of frequent and marked changes in lake depth up to 12 m 10014c yr probably caused by short term changes in effective precipitation we studied a 5 45 m long core comprising a basal layer of inorganic mud overlain by a succession of layers of calcareous laminated and nonlaminated organic mud marl and sand we used mazama tephra to adjust nine radiocarbon ages for the hardwater effect meromixis developed ca 900014c yr b p and the lake has been episodically meromictic for about half the time since because of close linkages between sediments and depositional environments in meromictic and saline lakes we infer that laminated sediments indicate meromictic conditions and high lake levels ca 12 m water depth whereas thick marl layers and nonlaminated sediments indicate nonmeromictic conditions and thus low lake levels

late quaternary climatic change on the american north pacific coast temporal changes in solar radiation caused by variations in the earth s orbit figure prominently in current quaternary climate theory1 4 experimental design of atmospheric circulation models emphasizes the importance of solar radiation in the heating of interglacial land and ocean surfaces at different seasons of the year whereby monsoon type circulation seasonal shifting of regional cyclonic and anticyclonic centres develops while during glacial ages seasonality is greatly modified by the influence of ice sheets5 7 we investigated the late quaternary climate of the north pacific where according to modelling solar radiation in the early holocene at the time of the summer solstice is high and in the late holocene is relatively low we compared quantitative temperature and precipitation estimates from southern alaska obtained by application of transfer functions to fossil pollen records with estimates from western washington8 and southern british columbia9 data extending over 10 000 years show a broadly consistent pattern of climatic change in general agreement with predicted variations in solar radiation and their effect on atmospheric circulation and seasonal duration of pressure systems over the north pacific ocean in the early holocene as monsoon type circulation became established with melting of glaciers the subtropical north pacific anticyclone annually regulated climate for a longer period at higher latitudes than at present so that warmth and dryness high summer radiation increased in southern alaska the aleutian low pressure centre locus of cyclonic storm activity intensified during the late holocene resulting in colder and more humid coastal climate low summer radiation over much of the year and increased frequency of glacier growth in the cordillera

late quaternary vegetation and climate history near little lake central coast range oregon pollen and plant macrofossils recovered from little lake oregon provide the first record of late quaternary climate and vegetation changes in oregon9s central coast range the pollen data suggest that the period from ca 42 000 to 24 770 yr b p featured an open forest of western white pine western hemlock and fir the inferred climate was cooler and wetter than today the full glacial period was characterized by a parkland of spruce lodgepole pine and mountain hemlock which suggests that the climate was colder and possibly drier than today the oregon coast range was not a glacial refugium for temperate conifers as has been proposed by 16 000 yr b p the pollen and plant macrofossil data suggest the development of a montane forest composed of pine fir western hemlock and mountain hemlock temperate taxa were present in the vegetation at 13 500 yr b p during a period of climatic amelioration a reversal in this warming trend may have occurred between 11 000 and 10 500 yr b p when pine western and mountain hemlock and spruce were slightly more abundant early holocene forests featured douglas fir red alder and bracken fern implying more severe summer drought and more frequent fires after 5600 yr b p douglas fir western hemlock and western red cedar dominated the record marking the introduction of the present day cool moist climate however during the past 2800 yr increased douglas fir and decreased cedar suggest the possibility of reduced effective moisture at little lake

early holocene limnological and climatic variability in the northern great plains information on the timing and direction of climatic and environmental change on a millennial scale exists for many regions of north america whereas little is known about decadal to centennial scale variability here we present a high resolution analysis of diatom inferred salinity from a site in the northern great plains to reconstruct multidecadal and centennial scale climatic patterns during the early holocene the diatominferred salinity indicates a transition from fresh to highly saline conditions between c 13 400 and 7700 cal yr bp which suggests a major shift in climate from wet to dry conditions the overall trend toward increasing salinity is interrupted by several freshwater intervals between c 9800 and 7950 cal yr bp which may be the result of an increase in the frequency of monsoonal flow from the gulf of mexico the early holocene is considered to be a time of rapid change in climate and vegetation within the holocene although rates of change in the moon lake diatom assemblages were hi

a 14 300 year long record of fire vegetation climate linkages at battle ground lake southwestern washington high resolution macroscopic charcoal analysis was used to reconstruct a 14 300 year long fire history record from the lower columbia river valley in southwestern washington which was compared to a previous vegetation reconstruction for the site in the late glacial period ca 14 300 13 100 cal yr bp pinus picea dominated parkland supported little to no fire activity from the late glacial to the early holocene ca 13 100 10 800 cal yr bp pseudotsuga abies dominated forest featured more frequent fire episodes that burned mostly woody vegetation in the early to middle holocene ca 10 800 5200 cal yr bp quercus dominated savanna was associated with frequent fire episodes of low to moderate severity with an increased herbaceous i e grass charcoal content from the middle to late holocene ca 5200 cal yr bp to present forest dominated by pseudotsuga thuja type and tsuga heterophylla supported less frequent but mostly large or high severity fire episodes fire episodes were least frequent but were largest or most severe after ca 2500 cal yr bp the fire history at battle ground lake was apparently driven by climate directly through the length and severity of the fire season and indirectly through climate driven vegetation shifts which affected available fuel biomass

nomenclature and resolution in holocene glacial chronologies most quaternary research in canada during the first half of the twentieth century focused on pleistocene glaciation given the dramatic shifts in climate during the pleistocene it is not surprising that the holocene was viewed as a time of benign climate holocene climate variability was first recognized around the middle of the century when paleoecologists found evidence that the early part of the epoch was warmer and drier than the later part in 1970s and 1980s another generation of geologists geographers and botanists began to recognize more complexity in holocene climate and vegetation in western canada several millennial scale glacier advances postdating the early holocene warm interval were defined including the garibaldi phase 6 9 5 6 ka the tiedemann peyto advance 3 5 1 9 ka and the little ice age ad 1200 1900 subsequently application of dendrochronological techniques and stratigraphic studies in glacier forefields showed that the little ice age was itself more complex than previously thought during that 700 year period glaciers repeatedly advanced and retreated in response to climatic variability on time scales ranging from centuries to decades recent work shows that the glacier record of the garibaldi phase and the tiedemann and peyto advances are similar in complexity to the little ice age with multiple advances of glaciers separated by intervals of more restricted ice cover researchers have also identified other times in the holocene when glaciers expanded from restricted positions 8 20 4 90 3 80 and 1 70 1 40 ka continued research undoubtedly will reveal additional complexities but with what is currently known the appropriateness of terms such as tiedemann advance peyto advance and little ice age can be questioned only short periods of time separate these episodes as currently defined and it seems likely that intervals of restricted glacier cover within each of these millennial length intervals are just as long as the intervals separating them

late quaternary dynamics of forest vegetation on northern vancouver island british columbia canada abstract pollen analysis of radiocarbon dated lake sediment from northern vancouver island southwest british columbia reveals regional changes in forest vegetation over the last 12 200 14c yr 14 900 cal yr between at least 12 200 and 11 700 14c yr bp 14 900 13 930 cal yr bp open woodlands were dominated by pinus contorta alnus crispa and various ferns as p contorta decreased in abundance alnus rubra and more shade tolerant conifers i e picea and tsuga mertensiana increased increases in t mertensiana p contorta and a crispa pollen accumulation rates pars between 10 600 and 10 400 14c yr bp 11 660 11 480 cal yr bp reflect a cool and moist climate during the younger dryas chronozone orbitally induced warming around 10 000 14c yr bp 11 090 cal yr bp allowed the northward extension of pseudotsuga menziesii although picea tsuga heterophylla and a rubra dominated early holocene forests by 7500 14c yr bp 8215 cal yr bp shade tolerant t heterophylla was the dominant forest tree cupressaceae thuja plicata and chamaecyparis nootkatensis was present by 7500 14c yr bp but reached its maximum after 3500 14c yr bp 3600 cal yr bp when a cooler and wetter regional climate facilitated the development of temperate rainforest the highest rates of vegetation change are associated with lateglacial climate change and species with rapid growth rates and short life spans

sensitivity of late glacial and holocene climates to the combined effects of orbital parameter changes and lower boundary condition changes snapshot simulations with a general circulation model for 18 9 and 6 ka bp

holocene tree line and climate change on the queen charlotte islands canada palynological study of two subalpine ponds on the queen charlotte islands reveals changes in tree line and climate during the holocene the findings agree with previous reconstructions from nearby louise pond on the queen charlotte islands that suggest a warmer than present climate and higher than present tree lines in the early holocene ca 9600 660014c yr b p basal ages at sc1 pond and shangri la bog indicate that the basins did not hold permanent water before 720014c yr b p consistent with a warmer and drier early holocene previously inferred from louise pond pollen and plant macrofossils indicate the initial establishment of subalpine conditions by 6090 9014c yr b p similar to the 5790 13014c yr b p age for cooling inferred from louise pond conditions similar to present were established at sc1 pond by 3460 10014c yr b p confirming the previous estimate of 340014c yr b p at louise pond this 340014c yr b p vegetation shift on the queen charlotte islands corresponds with the beginning of the tiedemann glacial advance in the south coastal mountains of british columbia ca 330014c yr b p the peyto and robson glacial advances between 3300 and 280014c yr b p in the rocky mountains and climatic cooling inferred from palynological studies throughout southern british columbia northern washington and southeast alaska these findings confirm that changes in regional climate influenced changes in vegetation in coastal british columbia