Final Report for DOE contract DE-FG02-98ER62609

• Main Author: Webb, Thompson, III
• Language: unknown
• Published: 2016
• Subjects: 54 ENVIRONMENTAL SCIENCES; Pacific; Ice Sheet; North Atlantic; Sea ice
• Online Access: http://www.osti.gov/servlets/purl/1048699; https://www.osti.gov/biblio/1048699; https://doi.org/10.2172/1048699

Several publications document, analyze, and map the paleoclimatic data available for the last glacial maximum (LGM) 21,000 years ago. Data coverage is fairly extensive for North America, Eurasia, and Africa. The data show much lower temperatures for that time in earth history. These data were used to check climate model simulations for the LGM. Simulations forced by the CLIMAP SST for the LGM, where the west/east SST gradient across the Pacific is reduced compared to present, produce a reduction in the strength of the trade winds and a decrease in the west/east slope of the equatorial thermocline that is incompatible with thermocline depths newly inferred from foraminiferal assemblages. Stronger than-present trade winds, and a more realistic simulation of the thermocline slope, are produced when eastern Pacific SSTs are 2oC cooler than western Pacific SSTs. Sensitivity experiments for the model simulations of the LGM were also used to show which aspects of the climate boundary conditions produced various changes in model simulations for the LGM. An experiment which has the LGM ice sheets for the Northern Hemisphere but no Eurasian ice sheet shows that the downstream cooling in Asia is largely dependent on sea-ice growth in the North Atlantic, which is a product of the Laurentide ice sheet. Weaker Asian monsoons develop as a result of this downstream cooling, which is largest for low Laurentide ice sheets of large areal extent.