Last glacial maximum

Fluxes of continental dust preserved in ice cores of Greenland and Antarctica suggest a 30-fold increase in dust flux during the last Glacial Maximum. Dramatic increases in new biological production in the HNLC regions may have resulted, resulting in the draw-down of atmospheric CO2 (Martin, 1990). 

Jouzel, J., Merlivat, L., and Lorius, C. (1982). Deuterium excess in an East Antarctic ice core suggests higher relative humidity at the oceanic surface during the last glacial maximum. Nature 299, 688-691. 

Stute, M., Schlosser, P., Talma, A. S. et al. (1995). Uniform cooling of the low latitude continents during the last glacial maximum. EOS 76, F296. 

Sealy, J.C. 1996 Seasonality of rainfall around the Last Glacial Maximum as reconstructed from carbon isotope analyses of animal bones from Nelson Bay Cave. South African Journal of Science 92 441 144. 

In addition to these variables, the interpretation of 0-values in carbonate shells is complicated by the sea water carbonate chemistry. In culture experiments with living foraminifera Spero et al. (1997) demonstrated that higher pH-values or increasing COj" concentrations result in isotopically lighter shells, which is due to changing sea water chemistry. As shown by Zeebe (1999) an increase of sea water pH by 0.2-0.3 units causes a decrease in of about 0.2-0.3%c in the shell. This effect has to be considered for instance when samples from the last glacial maximum are analyzed. 

Thompson P, Schwarcz HP, Ford DE (1974) Continental Pleistocene climatic variationa from speleothem age and isotopic data. Science 184 893-895 Thompson LG, Mosley-Thompson E, Henderson KA (2000) Ice-core palaeoclimate records in tropical South America since the last glacial maximum, J Quaternary Sci 15 377-394 Thompson LG, et al, (2006) Abrupt tropical climate change past and present, Proc Nat Acad Sci 103 10536-10543... 

Bush, A. B. G., and S. G. H. Philander, The Role of Ocean-Atmosphere Interactions in Tropical Cooling during the Last Glacial Maximum, Science, 279, 1341-1344 (1998). 

Figure 6.1. Ecosystem area and soil carbon content to 3-m depth. Lower Panel Global areal extent of major ecosystems, transformed by land use in yellow, untransformed in purple. Data from Hassan et al. (2005) except for Mediterranean-climate ecosystems transformation impact is from Myers et al. (2000) and ocean surface area is from Hassan et al. (2005). Upper Panel Total C stores in plant biomass, soil, yedoma/permafrost. D, deserts G S(tr), tropical grasslands and savannas G(te), temperate grasslands ME, Mediterranean ecosystems F(tr), tropical forests F(te), temperate forests F(b), boreal forests T, tundra FW, freshwater lakes and wetlands C, croplands O, oceans. Data are from Sabine et al. (2004), except C content of yedoma permafrost and permafrost (hght blue columns, left and right, respectively Zimov et al., 2006), and ocean organic C content (dissolved plus particulate organic Denman et al., 2007). This figure considers soil C to 3-m depth (Jobbagy and Jackson, 2000). Approximate carbon content of the atmosphere is indicated by the dotted lines for last glacial maximum (LGM), pre-industrial (P-IND) and current (about 2000). Reprinted from Fischlin et al. (2007) in IPCC (2007). See color insert.

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.

Figure 4.8 shows an example of the estimation of paleotemperature based on noble gas measurements in the groundwater of some aquifers in Texas (State et al., 1992). Paleotemperatures estimated from the noble gas concentration shows a large drop (about 5.2°C) at the distance 30km away from the recharge area [Figure 4.8(c)], which corresponds to an age between 12,000 and 17,000 years, close to the last glacial maximum (about 18,000 years ago). 

Paleotemperatures During the Last Glacial Maximum Real or Apparent Differences Between Terrestrial and Oceanic Evidence... 

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... 

Answer 15.5 Yes, it seems ideal, as it provides an unmixed sample of an established age, coinciding with the last glacial maximum (i.e., a phase of an extreme climate). A higher concentration of the heavier atmospheric noble gases is expected, and if found, it will support the colder climate reconstruction. 

Keywords Photocatalysis Photo splitting Solar energy utilization H2O, CO2, CO, N2 Last Glacial Maximum. 

Mahowald, N., et al. (1999). Dust sources and deposition during the last glacial maximum and current climate A comparison of model results with paleodata from ice cores and marine sediments. 

Moore, J. K., Abbott, M. R., Richman, J. G., Nelson, D. M. (2000). The Southern Ocean at the last glacial maximum A strong sink for atmospheric carbon dioxide. Global Biogeochem. Cycles 14, 455-475. 

Figure 34.8 Plots of c5 Nbuik versus sediment age over the past 50,000 years for cores from the Mexican margin (Ganeshram et af, 1995), the Somali margin of the Arabian Sea (Ivanochko etal., 2005) and the South China Sea (Kienast, 2000). The Last Glacial Maximum (LGM) and Younger Dryas (YD) cold intervals are indicated hy the hlue shading. The offsets among the records...

Loubere, P., Mekik, F., Francois, R., and Pichat, S. (2004). Export fluxes of calcite in the eastern equatorial Pacific from the last glacial maximum to present. Paleoceanography 19(2), doi 10.1029/ 2003PA000986. 

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