Bromwich (2004), Atmospheric response to modified CLIMAP ocean boundary conditions during the Last Glacial Maximum

• Main Authors: E. Richard Toracinta, Robert J. Oglesby, David H. Bromwich
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Pacific; North Atlantic; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.594.3071; http://ruby.fgcu.edu/courses/twimberley/EnviroPhilo/CLIMAP.pdf

Global climate simulations are conducted to examine the sensitivity of the Last Glacial Maximum (LGM) climate to prescribed sea surface temperatures (SSTs) that are modified from the Climate: Long-range Investi-gation, Mapping, and Prediction (CLIMAP) study. Based on the consensus from various LGM proxy data, the SSTs are cooled by 48C uniformly in the Tropics (308N–308S) relative to CLIMAP, and the high-latitude sea ice extent is reduced. Compared to results from a simulation with CLIMAP SSTs, the modified LGM SSTs cause significant opposing changes in the hemispheric and regional-scale atmospheric circulation, which are most pronounced in the winter hemisphere. For instance, there is significant weakening of the midlatitude circulation and reduction of 500-hPa eddy kinetic energy and midlatitude precipitation resulting from the decreased me-ridional temperature gradient in the modified SST simulation. In contrast, reduced sea ice extent during the boreal winter causes increased regional baroclinicity and intensified atmospheric circulation in the western North Pacific and the North Atlantic. Cooled tropical SSTs also increase the land–ocean temperature contrast, which strengthens the Asian summer monsoon circulation. Both LGM simulations produce enhanced low-level con-vergence and increased precipitation along the South Pacific convergence zone (SPCZ) relative to present day, despite the cooler LGM climate. The SPCZ orientation and intensity are closely linked to the distribution of