Paleo-climate of the Boise area, Idaho from the last glacial maximum to the present based on groundwater δ2H and δ18O compositions

2009 ◽  
Vol 71 (2) ◽  
pp. 172-180 ◽  
Author(s):  
Melissa E. Schlegel ◽  
Alan L. Mayo ◽  
Steve Nelson ◽  
Dave Tingey ◽  
Rachel Henderson ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Deuterium Excess ◽  
Moisture Source ◽  
Last Glacial ◽  
Stable Isotopic Composition ◽  
Stable Isotopic ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractA 30 ka paleo-climate record of the Boise area, Idaho, USA has been delineated using groundwater stable isotopic compositions. Groundwater ages are modern (cold batholith), 5–15 ka (thermal batholith), 10–20 ka (frontal fault), and 20–30 ka (Snake River plain thermal). The stable isotopic composition of groundwaters have been used as a surrogate for the stable isotopic composition of precipitation. Using δ2H and δ18O compositions, local groundwater lines (LGWL's) were defined for each system. Each LGWL has been evaluated with defined slopes of 6.94 and 8, respectively, and resulting deuterium excess values (d) were found for each groundwater system for each slope. Time dependent changes in moisture source humidity and temperature, and Boise area recharge temperatures, calculated from stable isotopic data and the deuterium excess factors, agree with previous paleo-climate studies. Results indicate that from the last glacial maximum to the present time the humidity over the ocean moisture source increased by 9%, sea surface temperature at the moisture source increased 6–7°C, and local Boise temperature increased by 4–5°C. A greater increase of temperature at the moisture source as compared to the Boise area may impart be due to a shift in the moisture source area.

The oxygen isotopic composition of seawater during the Last Glacial Maximum

2002 ◽  
Vol 21 (1-3) ◽  
pp. 331-342 ◽  
Author(s):  
Daniel P. Schrag ◽  
Jess F. Adkins ◽  
Katherine McIntyre ◽  
Jane L. Alexander ◽  
David A. Hodell ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Last Glacial Maximum ◽  
Oxygen Isotopic Composition ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Oxygen Isotopic ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals A modeling sensitivity study of the influence of the Atlantic meridional overturning circulation on neodymium isotopic composition at the Last Glacial Maximum

2008 ◽  
Vol 4 (3) ◽  
pp. 191-203 ◽  
Author(s):  
T. Arsouze ◽  
J.-C. Dutay ◽  
M. Kageyama ◽  
F. Lacan ◽  
R. Alkama ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Last Glacial Maximum ◽  
Ocean Circulation ◽  
Glacial Maximum ◽  
Meridional Overturning Circulation ◽  
Oceanic Circulation ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial ◽  
Modern Control

Abstract. Using a simple parameterisation that resolves the first order global Nd isotopic composition (hereafter expressed as εNd in an Ocean Global Circulation Model, we have tested the impact of different circulation scenarios on the εNd in the Atlantic for the Last Glacial Maximum (LGM), relative to a modern control run. Three different LGM freshwater forcing experiments are performed to test for variability in the εNd oceanic distribution as a function of ocean circulation. Highly distinct representations of the ocean circulation are generated in the three simulations, which drive significant differences in εNd, particularly in deep waters of the western part of the basin. However, at the LGM, the Atlantic is more radiogenic than in the modern control run, particularly in the Labrador basin and in the Southern Ocean. A fourth experiment shows that changes in Nd sources and bathymetry drive a shift in the εNd signature of the basin that is sufficient to explain the changes in the εNd signature of the northern end-member (NADW or GNAIW glacial equivalent) in our LGM simulations. All three of our LGM circulation scenarios show good agreement with the existing intermediate depth εNd paleo-data. This study cannot indicate the likelihood of a given LGM oceanic circulation scenario, even if simulations with a prominent water mass of southern origin provide the most conclusive results. Instead, our modeling results highlight the need for more data from deep and bottom waters from western Atlantic, where the εNd change in the three LGM scenarios is the most important (up to 3 εNd. This would also aid more precise conclusions concerning the evolution of the northern end-member εNd signature, and thus the potential use of εNd as a tracer of past oceanic circulation.

scholarly journals Influence of the Atlantic thermohaline circulation on neodymium isotopic composition at the Last Glacial Maximum – a modelling sensitivity study

2008 ◽  
Vol 4 (2) ◽  
pp. 309-333 ◽  
Author(s):  
T. Arsouze ◽  
J.-C. Dutay ◽  
M. Kageyama ◽  
F. Lacan ◽  
R. Alkama ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Last Glacial Maximum ◽  
Ocean Circulation ◽  
Glacial Maximum ◽  
Oceanic Circulation ◽  
Last Glacial ◽  
Deep Waters ◽  
The Impact ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. The oceanic neodymium isotopic composition (hereafter expressed as ε Nd) is modeled for the Last Glacial Maximum (LGM) using the coarse resolution Ocean Global Circulation Model NEMO–ORCA2°. This study focuses on the impact of changes in the overturning cell and circulation patterns between LGM and Holocene on ε Nd in the Atlantic basin. Three different LGM freshwater forcing experiments are performed to test the variability in ε Nd oceanic distribution as a function of ocean circulation. Highly distinct representations of ocean circulation are generated in the three simulations, which drive significant differences in ε Nd, particularly in deep waters of the western part of the basin. However, mean Atlantic LGM ε Nd values are remain half a unit more radiogenic than for the modern control run. A fourth experiment shows that changes in Nd sources and bathymetry drive a shift in the ε Nd signature of Northern end-members (NADW or GNAIW glacial equivalent) that is sufficient to explain the shift in mean ε Nd during our LGM simulations. None of our three LGM circulation scenarios gives a better agreement with the existing ε Nd paleo-data, as the model fails in reproducing the dynamical features of the area. Therefore, this study cannot indicate the likelihood of a given LGM oceanic circulation scenario. Rather, our modeling results highlight the need for data from western Atlantic deep waters, where the ε Nd gradient in the three LGM scenarios is the most important (up to 3 ε Nd). This would also aid more precise conclusions concerning the north end-member ε Nd signature evolution, and thus the potential use of ε Nd as a tracer of past oceanic circulation.

Reconstructions of the past distribution of Testudo graeca mitochondrial lineages in the Middle East and Transcaucasia support multiple refugia since the Last Glacial Maximum

2021 ◽  
pp. 10-17
Author(s):  
Oguz Turkozan
Keyword(s):  
Middle East ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Testudo Graeca ◽  
Last Glacial ◽  
The Past ◽  
Precipitation Seasonality ◽  
Multiple Refugia ◽  
The Last Glacial Maximum ◽  
The Last Glacial

A cycle of glacial and interglacial periods in the Quaternary caused species’ ranges to expand and contract in response to climatic and environmental changes. During interglacial periods, many species expanded their distribution ranges from refugia into higher elevations and latitudes. In the present work, we projected the responses of the five lineages of Testudo graeca in the Middle East and Transcaucasia as the climate shifted from the Last Glacial Maximum (LGM, Mid – Holocene), to the present. Under the past LGM and Mid-Holocene bioclimatic conditions, models predicted relatively more suitable habitats for some of the lineages. The most significant bioclimatic variables in predicting the present and past potential distribution of clades are the precipitation of the warmest quarter for T. g. armeniaca (95.8 %), precipitation seasonality for T. g. buxtoni (85.0 %), minimum temperature of the coldest month for T. g. ibera (75.4 %), precipitation of the coldest quarter for T. g. terrestris (34.1 %), and the mean temperature of the driest quarter for T. g. zarudyni (88.8 %). Since the LGM, we hypothesise that the ranges of lineages have either expanded (T. g. ibera), contracted (T. g. zarudnyi) or remained stable (T. g. terrestris), and for other two taxa (T. g. armeniaca and T. g. buxtoni) the pattern remains unclear. Our analysis predicts multiple refugia for Testudo during the LGM and supports previous hypotheses about high lineage richness in Anatolia resulting from secondary contact.

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