bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lake-Level Reconstruction and Paleohydrology of Birch Lake, Central Alaska, Based on Seismic Reflection Profiles and Core Transects
Authors: Abbott Mark B. , Finney Bruce P. , Edwards Mary E. , Kelts Kerry R. 
Published: September 2002

AbstractLake-level history for Birch Lake, Alaska, was reconstructed using seismic profiles and multiproxy sedimentary analyses including sedimentology, geochemistry, magnetic susceptibility, and palynology. Twenty-two seismic profiles (18 km total) and eight sediment cores taken from the lake margin to its depocenter at 13.5 m provide evidence for low lake stands during the late Pleistocene and Holocene. Thirty-one AMS radiocarbon dates of macrofossils and pollen provide a century-scale chronology. Prior to 12,70014C yr B.P., the lake, which now overflows, was either seasonally dry or desiccated for prolonged periods, indicating a severe period of aridity. Lake level rose more than 18 m between 12,700 and 12,20014C yr B.P. before falling to 17 m below the level of overflow. Between 11,600 and 10,60014C yr B.P. the water remained between 14 and 17 m below the overflow level. Onlap sedimentary sequences were formed during a transgression phase between 10,600 and 10,00014C yr B.P. Between 10,000 and about 880014C yr B.P. the lake was between 6 and 9 m below the overflow level. Lake level again rose, approaching the overflow level, between 8800 and 800014C yr B.P. Seismic and core evidence of minor erosional events suggest lowstands of 2–6 m until 480014C yr B.P. There have been no prolonged periods of lake-level depression since that time. The major restructuring of the climate system during deglaciation evidently generated a complex set of fluctuations in effective moisture in interior Alaska, which likely affected eolian processes and vegetation development, as well as lake levels.
Holocene Environmental Changes from the Rio Curuá Record in the Caxiuanã Region, Eastern Amazon Basin
Authors: Behling Hermann , da Costa Marcondes Lima 
Published: September 2002

AbstractHolocene environments have been reconstructed by multiproxy studies of an 850-cm-long core from Rio Curuá dating to >800014C yr B.P. The low-energy river lies in the eastern Amazon rain forest in the Caxiuanã National Forest Reserve, 350 km west of Belem in northern Brazil. Sedimentological, mineralogical, and geochemical dates demonstrate that the deposits correspond to two different environments, sediments of an active river before 800014C yr B.P. and later a passive river system. The pollen analytical results indicate four different local and regional Holocene paleoenvironmental periods: (1) a transition to a passive fluvial system and a well-drained terra firme (unflooded upland) Amazon rain forest with very limited development of inundated forests (várzea and igapó) (>7990–703014C yr B.P.); (2) a sluggish river with a localMauritiapalm-swamp and similar regional vegetation, as before (7030–597014C yr B.P.); (3) a passive river, forming shallow lake conditions and with still-abundant terra firme forest in the study region (5970–247014C yr B.P.); and (4) a blocked river with high water levels and marked increase of inundated forests during the last 247014C yr B.P. Increased charcoal during this last period suggests the first strong presence of humans in this region. The Atlantic sea level rise was probably the major factor in paleoenvironmental changes, but high water stands might also be due to greater annual rainfall during the late Holocene.
Holocene Treeline History and Climate Change Across Northern Eurasia
Authors: MacDonald Glen M. , Velichko Andrei A. , Kremenetski Constantine V. , Borisova Olga K. , Goleva Aleksandra A. , Andreev Andrei A. , Cwynar Les C. , Riding Richard T. , Forman Steven L. , Edwards Tom W.D. , Aravena Ramon , Hammarlund Dan , Szeicz Julian M. , Gattaulin Valery N. 
Published: September 2002

AbstractRadiocarbon-dated macrofossils are used to document Holocene treeline history across northern Russia (including Siberia). Boreal forest development in this region commenced by 10,000 yr B.P. Over most of Russia, forest advanced to or near the current arctic coastline between 9000 and 7000 yr B.P. and retreated to its present position by between 4000 and 3000 yr B.P. Forest establishment and retreat was roughly synchronous across most of northern Russia. Treeline advance on the Kola Peninsula, however, appears to have occurred later than in other regions. During the period of maximum forest extension, the mean July temperatures along the northern coastline of Russia may have been 2.5° to 7.0°C warmer than modern. The development of forest and expansion of treeline likely reflects a number of complimentary environmental conditions, including heightened summer insolation, the demise of Eurasian ice sheets, reduced sea-ice cover, greater continentality with eustatically lower sea level, and extreme Arctic penetration of warm North Atlantic waters. The late Holocene retreat of Eurasian treeline coincides with declining summer insolation, cooling arctic waters, and neoglaciation.
Holocene Paleohydrology and Paleoclimate at Treeline, North-Central Russia, Inferred from Oxygen Isotope Records in Lake Sediment Cellulose
Authors: Wolfe Brent B. , Edwards Thomas W. D. , Aravena Ramon , Forman Steven L. , Warner Barry G. , Velichko Andrei A. , MacDonald Glen M. 
Published: September 2002

AbstractLake-water oxygen-isotope histories for three lakes in northern Russia, derived from the cellulose oxygen-isotope stratigraphies of sediment cores, provide the basis for preliminary reconstruction of Holocene paleohydrology in two regions along the boreal treeline. Deconvolution of shifting precipitation δ18O from secondary evaporative isotopic enrichment is aided by knowledge of the distribution of isotopes in modern precipitation, the isotopic composition of paleo-waters preserved in frozen peat deposits, as well as other supporting paleoclimatic information. These data indicate that during the early Holocene, when the boreal treeline advanced to the current arctic coastline, conditions in the lower Yenisey River region were moist compared to the present, whereas greater aridity prevailed to the east near the lower Lena River. This longitudinal moisture gradient is consistent with the suggestion that oceanic forcing (increased sea-surface temperatures in the Nordic Seas and reduced sea-ice cover) was a major contributor to the development of a more maritime climate in western Eurasia, in addition to increased summer insolation. East of the Taimyr Peninsula, large tracts of the continental shelf exposed by glacial sea-level drawdown may have suppressed maritime climatic influence in what are now coastal areas. In contrast, during the late Holocene the two regions have apparently experienced coherent shifts in effective moisture. The similarity of the records may primarily reflect reduced North Atlantic influence in the Nordic Seas and southward retreat of coastline in eastern Siberia, coupled with declining summer insolation.
GISP2 Oxygen Isotope Ratios
Authors: Stuiver Minze , Grootes Pieter M. 
Published: September 2002

AbstractThe GISP2 oxygen isotope record, with its high-resolution detail, yields crucial information on past climate change. The glacial δ18O oscillations of the GISP2 core, with their very fast onsets, are templates of a prototype oscillation of variable duration with an amplitude of 3.9‰. The halfway mark of the cold–warm transition is reached in 2 years; the top is reached in 50 years. The δ18O–time gradient of the leading front is about 7.8‰ per 100 yr. After reaching the top, δ18O slowly declines by −0.14‰ per 100 yr. The duration of δ18O decline varies from a couple of centuries for fast oscillations to about 4000 yr for slower ones. The subsequent δ18O downturn during the warm–cold transition has a δ18O–time gradient of −3.2‰ per 100 yr and lasts about 80 yr.
Late-Glacial and Early Holocene Vegetation and Climate Change near Owens Lake, Eastern California
Authors: Mensing Scott A. 
Published: September 2002

AbstractPollen and algae from Owens Lake in eastern California provide evidence for a series of climatic oscillations late in the last glaciation. Juniper woodland, which dominated the Owens Valley from 16,200 to 15,500 cal yr B.P., suggests much wetter conditions than today. Although still wetter and cooler than today, the area then became fairly warm and dry, with woodland being replaced by shrubs (mainly sagebrush) from 15,500 to 13,100 cal yr B.P. Next, Chenopodiaceae (shadscale) increased, woody species declined, and lake levels fell—all evidence for a brief (ca. 100–200 yr) drought about 13,000 cal yr B.P. The climate continued to oscillate between wet and dry from 13,000 to 11,000 cal yr B.P. After 11,000 cal yr B.P., low lake levels and the increased dominance of desert shrubs indicate the beginning of warm, dry Holocene conditions. The region's climate was unstable during the Younger Dryas but uncertainities in dating prevent identification of the Younger Dryas interval in the Owens Lake record. Comparison of the Owens Lake record with studies in the Sierra Nevada and Great Basin suggest that the climate was generally wetter between 13,000 and 11,000 cal yr B.P., with warmer summers, although no consistent pattern of climate change emerges.
Pacific Sea Surface Temperature Forcing Dominates Orbital Forcing of the Early Holocene Monsoon
Authors: Bush Andrew Basil George 
Published: September 2002

AbstractOrbital forcing is known to play a primary role in regulating the strength of the south Asian monsoon circulation. In this study, a comparison is made between orbital forcing and Pacific sea surface temperature (SST) forcing of the monsoon through a sequence of atmospheric general circulation model experiments configured for 6,000 and 9,000 yr B.P. Early–mid Holocene orbital parameters are shown to increase continental seasonality as well as the meridional mean, the zonal mean, and the summer monsoon circulations. Winds in the southeast Asian monsoon are weakened by warm Pacific SST to such an extent that the increase in strength caused by early Holocene orbital parameters is offset. These results imply that SSTs are potentially as important as orbital parameters in governing the monsoon and that more data—particularly from the equatorial Pacific—are crucial to deciphering Holocene climate.
Multiproxy Record of Late Pleistocene–Holocene Climate and Vegetation Changes from a Peat Bog in Patagonia
Authors: Pendall Elise , Markgraf Vera , White James W. C. , Dreier Mark , Kenny Ray 
Published: September 2002

AbstractPollen assemblage changes and stable hydrogen isotope analysis of mosses (Sphagnum magellanicum and Drepanocladus s.l.) from a bog in Tierra del Fuego, Argentina, provided independent proxies for reconstructing changes in effective moisture and temperature over the past 16,000 cal yr B.P. A deterministic model was used to reconstruct the stable hydrogen isotope composition of meteoric water from the D/H ratios of bog mosses over the last 16,000 years. Abrupt changes in temperature, as recorded in D/H ratios of moss cellulose, were accompanied by synchronous changes in vegetation composition during the late Pleistocene and early and middle Holocene, when moisture levels were lower than today. In contrast, temperature variability during the late Holocene was not accompanied by comparable vegetation changes. In particular, grass pollen (Poaceae) increased during periodic cold spells between 15,000 and 11,000 cal yr B.P., but a cold spell of similar magnitude ca. 2000 cal yr B.P. did not appear to affect vegetation. During the late Pleistocene, the isotopic record from the peat core shows variations similar to the D/H ratios in the Antarctic Taylor Dome ice core. However, the timing of the changes in the Harberton record is more in line with the timing of other Southern Hemisphere records.
Rates of Sediment Supply to Arroyos from Upland Erosion Determined Usingin SituProduced Cosmogenic10Be and26Al
Authors: Clapp Erik M. , Bierman Paul R. , Nichols Kyle K. , Pavich Milan , Caffee Marc 
Published: September 2002

AbstractUsing10Be and26Al measured in sediment and bedrock, we quantify rates of upland erosion and sediment supply to a small basin in northwestern New Mexico. This and many other similar basins in the southwestern United States have been affected by cycles of arroyo incision and backfilling several times in the past few millennia. The sediment generation (275 ± 65 g m−2yr−1) and bedrock equivalent lowering rates (102 ± 24 m myr−1) we determine are sufficient to support at least three arroyo cycles in the past 3,000 years, consistent with rates calculated from a physical sediment budget within the basin and regional rates determined using other techniques. Nuclide concentrations measured in different sediment sources and reservoirs suggest that the arroyo is a good spatial and temporal integrator of sediment and associated nuclide concentrations from throughout the basin, that the basin is in steady-state, and that nuclide concentration is independent of sediment grain size. Differences between nuclide concentrations measured in sediment sources and reservoirs reflect sediment residence times and indicate that subcolluvial bedrock weathering on hillslopes supplies more sediment to the basin than erosion of exposed bedrock.
Late Quaternary Paleoclimate in Semiarid Northeastern Brazil from U-Series Dating of Travertine and Water-Table Speleothems
Authors: Auler Augusto S. , Smart Peter L. 
Published: September 2002

AbstractFossil travertine and subaqueous speleothems in presently dry caves suggest periods of enhanced ground-water recharge during the Quaternary Period in semiarid northeastern Brazil. Travertine deposits and water-table speleothems were dated by the 230Th/234U technique, yielding new evidence for the timing of past periods of increased rainfall. The travertine was deposited in two distinct phases, extensive in situ deposits during marine isotope stage 2 and fragmentary, indurated deposits dating to ca. 400,000 yr B.P. (possibly marine isotope stage 10 or 12). Dating of water-table speleothems showed that the regional water table was 13±1 m above the present level at the last glacial maximum. A second site yielded ages suggesting a still higher water table during marine isotope stage 6. These new data demonstrate that northeastern Brazil did not follow the general pattern of a dry last glacial maximum, as suggested by other continental records in Amazonia and southeastern Brazil, and as depicted in recent General Circulation Model (GCM) simulations. Our results thus indicate that significant variability in regional rainfall patterns occurred in the area during glaciations and caution against overgeneralization of paleoclimate patterns.
Extensive Early and Middle Wisconsin Glaciation on the Western Olympic Peninsula, Washington, and the Variability of Pacific Moisture Delivery to the Northwestern United States
Authors: Thackray Glenn D. 
Published: September 2002

AbstractLarge glaciers descended western valleys of the Olympic Mountains six times during the last (Wisconsin) glaciation, terminating in the Pacific coastal lowlands. The glaciers constructed extensive landforms and thick stratigraphic sequences, which commonly contain wood and other organic detritus. The organic material, coupled with stratigraphic data, provides a detailed radiocarbon chronology of late Pleistocene ice-margin fluctuations. The early Wisconsin Lyman Rapids advance, which terminated prior to ca. 54,000 14C yr B.P., represented the most extensive ice cover. Subsequent glacier expansions included the Hoh Oxbow 1 advance, which commenced between ca. 42,000 and 35,000 14C yr B.P.; the Hoh Oxbow 2 advance, ca. 30,800 to 26,300 14C yr B.P.; the Hoh Oxbow 3 advance, ca. 22,000–19,300 14C yr B.P.; the Twin Creeks 1 advance, 19,100–18,300 14C yr B.P.; and the subsequent, undated Twin Creeks 2 advance. The Hoh Oxbow 2 advance represents the greatest ice extent of the last 50,000 yr, with the glacier extending 22 km further downvalley than during the Twin Creeks 1 advance, which is correlative with the global last glacial maximum. Local pollen data indicate intensified summer cooling during successive stadial events. Because ice extent was diminished during colder stadial events, precipitation—not summer temperature—influenced the magnitude of glaciation most strongly. Regional aridity, independently documented by extensive pollen evidence, limited ice extent during the last glacial maximum. The timing of glacier advances suggests causal links with North Atlantic Bond cycles and Heinrich events.
A High-Resolution Sea-Surface Temperature Record from the Tropical South China Sea (16,500–3000 yr B.P.)
Authors: Steinke Stephan , Kienast Markus , Pflaumann Uwe , Weinelt Mara , Stattegger Karl 
Published: September 2002

AbstractThe timing and magnitude of sea-surface temperature (SST) changes in the tropical southern South China Sea (SCS) during the last 16,500 years have been reconstructed on a high-resolution,14C-dated sediment core using three different foraminiferal transfer functions (SIMMAX28, RAM, FP-12E) and geochemical (Uk′37) SST estimates. In agreement with CLIMAP reconstructions, both the FP-12E and the Uk′37SST estimates show an average late glacial–interglacial SST difference of 2.0°C, whereas the RAM and SIMMAX28 foraminiferal transfer functions show only a minor (0.6°C) or no consistent late glacial–interglacial SST change, respectively. Both the Uk′37and the FP-12E SST estimates, as well as the planktonic foraminiferal δ18O values, indicate an abrupt warming (ca. 1°C in <200 yr) at the end of the last glaciation, synchronous (within dating uncertainties) with the Bølling transition as recorded in the Greenland Ice Sheet Project 2 (GISP2) ice core, whereas the RAM-derived deglacial SST increase appears to lag during this event by ca. 500 yr. The similarity in abruptness and timing of the warming associated with the Bølling transition in Greenland and the southern SCS suggest a true synchrony of the Northern Hemisphere warming at the end of the last glaciation. In contrast to the foraminiferal transfer function estimates that do not indicate any consistent cooling associated with the Younger Dryas (YD) climate event in the tropical SCS, the Uk′37SST estimates show a cooling of ca. 0.2–0.6°C compared to the Bølling–Allerød period. These Uk′37SST estimates from the southern SCS argue in favor of a Northern Hemisphere-wide, synchronous cooling during the YD period.
Late Quaternary Sea-Level Change in South Africa
Authors: Ramsay Peter J. , Cooper J. Andrew G. 
Published: September 2002

AbstractA Late Quaternary sea-level curve for South Africa is presented on the basis of new and published data from a range of sea level indicators and a variety of locations. Available evidence suggests that sea level in South Africa broadly follows that described from the Caribbean but that deviations occur during sea-level highstands. During the last interglaciation (oxygen isotope stage 5) and the late Holocene, coastal emergence produced higher sea levels in South Africa than those identified in the Caribbean during the same time intervals. This is tentatively ascribed to predicted lithospheric deformation in continental margin settings.
Cyclo‐oxygenase‐2 inhibition increases blood pressure in rats
Authors: Höcherl Klaus , Endemann Dierk , Kammerl Martin C , Grobecker Horst F , Kurtz Armin 
Published: September 2002

It is known that nonselective cyclo‐oxygenase (COX) inhibitors have small but significant effects on blood pressure (BP), most notably in hypertensive patients on antihypertensive medication. Whether selective COX‐2 inhibitors also interfere with BP regulation is not well understood. Therefore, we aimed to examine the effect of chronic treatment with a selective COX‐2 inhibitor (rofecoxib) on systolic blood pressure (sBP) in normotensive Wistar‐Kyoto rats (WKY) and on the developmental changes of sBP in young spontaneously hypertensive rats (SHR). In addition, we investigated a possible influence of salt intake on the effects of COX‐2 inhibition on BP in these two rat strains.
Rofecoxib dose dependently increased sBP and decreased plasma levels of 6‐keto prostaglandin (PG)F1α in WKY rats fed a normal salt diet (0.6% NaCl, wt wt−1), without affecting serum thromboxane (TX)B2 levels.
Rofecoxib significantly elevated sBP in both rat strains fed normal salt or high salt diet (8% NaCl, wt wt−1), but not in rats on low salt intake (0.02% NaCl, wt wt−1).
Rofecoxib significantly decreased plasma levels of 6‐keto PGF1α in both rat strains fed normal or high salt diet, but not in rats during low salt intake.
Rofecoxib exerted no influence on the changes of body weight nor on water intake. Plasma renin activity (PRA) and renocortical renin mRNA abundance were not changed by rofecoxib, but plasma aldosterone concentration (PAC) was significantly reduced.
These results suggest that chronic inhibition of COX‐2 causes an increase of blood pressure that depends on prostacyclin synthesis. Furthermore, this increase is independent on genetic predisposition and can be prevented by salt deprivation. Since water intake and body weight gain were not changed by rofecoxib, fluid retention appears not to be a major reason for the development of hypertension. Similarly, an activation of the renin‐angiotensin‐aldosterone axis appears to be an unlikely candidate mechanism.

British Journal of Pharmacology (2002) 136, 1117–1126. doi:10.1038/sj.bjp.0704821
Characterization of GABAA receptor ligands in the rat cortical wedge preparation: evidence for action at extrasynaptic receptors?
Authors: Ebert B , I Storustovu S , Mortensen M , Frølund B 
Published: September 2002

GABAA receptor agonists have previously been characterized at human GABAA receptors expressed in Xenopus oocytes. The correlation between these data and functional in vivo data of 4,5,6,7‐tetrahydroisoxazolo[5,4‐c]pyridin‐3‐ol (THIP) has shown that THIP is 100 fold more potent in clinical studies than in oocytes.
THIP and a series of agonists (GABA, Isoguvacine), partial agonists (Imidazole acetic acid; P4S, 4‐PIOL, thio‐4‐PIOL) and one antagonist (SR95531) were characterized in the rat cortical wedge preparation using inhibition of spontaneous activity in Mg++ free medium as the measurable parameter.
Agonists were in general 40 times more potent in the wedge preparation than at α1β3γ2s containing receptors expressed in Xenopus oocytes, whereas the antagonist was equipotent under these two conditions.
Partial agonists with responses above 6% at α1β3γ2s containing receptors were full agonists in the rat cortical wedge preparation, whereas partial agonists with maximum responses below 6% behaved as partial agonists in the rat cortical wedge preparation.
These data suggest that only a small fraction of the GABAA receptors in the rat cortical wedge needs to be activated by GABAA agonists in order to obtain a maximum response. Results therefore indicate a significant contribution of extrasynaptic receptors to pharmacological activity of exogenous applied GABAA agonists in this system.

British Journal of Pharmacology (2002) 137, 1–8. doi:10.1038/sj.bjp.0704846