Temperature Last Glacial Maximum

Figure 6.2. (A) Variations in %N (which is proportional to C density) with precipitation along the 11 °C isotherm in the Great Plains of the United States. The humidity factor (NSQ, Niederschlag-Sattigungsdefizit from the German, or Meyer s quotient) is the total annual precipitation (mm) divided by the absolute saturation deficit of air (mm mercury). All soils were developed on loess deposits from the last glacial maximum. (B) Change in %N with precipitation along the 19 °C isotherm. Note that relative C density (estimated by assuming that the C/N ratio of SOM is fairly constant) is lower at higher mean annual temperature. Reprinted with permission from Jenny, H. (1941). Factors of Soil Formation, Dover Publications, New York.

Effects of this nature should be borne in mind when addressing an inconsistency between reconstructed oceanic and continental temperatures, as pointed out by Stute et al. (1995a). The authors reported a temperature decrease of about 5°C during the last glacial maximum, as recorded by noble gases in groundwaters at several locations in temperate countries, whereas the corresponding temperature decrease of the ocean surface was... 

Trend-Staid M. and Prell W. E. (2002) Sea surface temperature at the Last Glacial Maximum a reconstruction using the modern analog technique. Paleoceanography 17(4) 10.1029/ 2000PA000506. 

Adkins J. F. and Schrag D. P. (2001) Pore fluid constraints on deep ocean temperature and salinity during the Last Glacial Maximum. Geophys. Res. Lett. 28, 771—775. 

Biospheric carbon stocks reconstructed at the last glacial maximum comparison between general circulation models using prescribed and computed sea surface temperatures. Global Planet. Change 33, 117-138. 

More specific palaeotemperature data for individual halite crystals may be gleaned from fluid inclusion homogenisation temperatures, a technique which has been substantially refined since the 1990s (Roberts and Spencer, 1995 Lowenstein and Brennan, 2001). From a core spanning lOOka of saline deposition in Death Valley, Lowenstein et al. (1998) were able to reconstruct depositional temperatures for several intervals (with an expected lower value, at the Last Glacial Maximum), and to faithfully recover the known seasonal temperature range for a modern salt crust. 

The response to the Last Glacial Maximum in Eurasia (21,000 years ago) was lowering of the summer temperatures in Central Asia by 2-4°C compared to the... 

During the last glacial maximum (c. 18 ka) the mean surface temperature was some 5 °C lower than at present, but cooling of this extent cannot have been the result of C02 drawdown alone, because all the C02 would have had to be removed from the atmosphere. The c.30% reduction in atmospheric C02 concentration during the last glacial maximum compared to the Holocene preindustrial level (Archer Maier-Reimer... 

Fig. 1. The CLIMAP reconstruction of Last Glacial Maximum (LGM) August sea surface temperatures (SSTs) for the global ocean based on planktonic foraminiferal assemblage data. Modified after CLIMAP (1984 http // iridl.ldeo.columbia.edu).

Barker, S., Cacho, I., Benway, H. Tachikawa, K. 2005. Planktonic foraminiferal Mg/Ca as a proxy for past oceanic temperatures a methodological overview and data compilation for the Last Glacial Maximum. Quaternary Science Reviews, 24,821—834. 

Birchfield, G.E., 1987. Changes in deep-ocean water 5 0 and temperature from last glacial maximum to the present. Paleoceanography 2 431-442. 

Figure 21. Noble gas temperature record from the Aquia aquifer, Maryland (USA), modified from Aeschbach-Hertig et al. (2002b). The chronology for this record could be established by " He accumulation ages based on the assumption of pure in-situ production. Only data from Aquia aquifer wells that could consistently be interpreted are shown. Mean noble gas temperatures for selected groups of samples, thought to best represent the Holocene, last glacial maximum (LGM), and preceding last glacial period are indicated, as well as the derived Holocene-LGM temperature difference.

Figure 21.5 Estimate of surface temp>erature for the last 800,000 years, inferred from measurements of the ratio of O to 0 in fossil plankton that settled to the sea floor. The use of oxygen isotope ratios is based on the assumption that changes in global temperature approximately track changes in the global ice volume. Detailed studies for the last glacial maximum provide the temperature scale. Shown are changes in temperature (in C) from the modern value. Based on data from Imbrie et al. (1984) and presented by Crowley (1996).

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