HR: 11:35h
AN: GC12A-06    [Abstracts]
TI: Role of Ice Sheets in Thermohaline Circulation Changes Under High Atmospheric Carbon Dioxide Concentration
AU: * Yih, H
EM: hyungyih@yahoo.com
AF: Research Institute of Oceanography, 19-316B School of Earth and Environmental Sciences Seoul National University, San-56-1, Sillim-dong, Kwanak-gu, Seoul, 151-742, Korea, Republic of
AU: Oh, I S
EM: ois@storm.snu.ac.kr
AF: Research Institute of Oceanography, 19-316B School of Earth and Environmental Sciences Seoul National University, San-56-1, Sillim-dong, Kwanak-gu, Seoul, 151-742, Korea, Republic of
AU: Chan, W
EM: wlchan@jamstec.go.jp
AF: Frontier Research Center for Global Change, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, 236-0001, Japan
AU: Motoi, T
EM: tmotoi@mri-jma.go.jp
AF: Meteorological Research Institute, 1-1 Chang-Bong, Tsukuba, 305-0052, Japan
AB: Thermohaline circulation (THC) changes are considered for two experimental settings of Antarctic and Greenland ice sheets with the atmospheric carbon dioxide of 1200 ppm in GFDL atmosphere-ocean coupled model. The experimental settings are to figure out the role of the ice sheets in global climate system, in which they are present and completely removed. The coupled model consists of the atmosphere and oceans, as well as simple models of land surfaces and sea ice. Atmospheric distribution of predicted variables is represented by Rhomboidal 15 configuration and nine vertical levels. Oceanic variables in 12 vertical levels have horizontal resolution of 4.5 degree latitude and 3.75 degree longitude. Streamfunctions of zonal mean meridional circulation in model oceans are used as representing fields of the THC, which are constructed after reaching statistical equilibrium state at 3000 model years. Same restart file is used for the two runs, which is at approximately 10000 model years of integration with atmospheric carbon dioxide concentration of 300 ppm provided from GFDL/NOAA. The THC appears again, after weakening, strengthening, and rapid-increasing during the first 3000 model years. Analysis periods of the equilibrium state are from 3000 to 10000 model years. Streamfunctions of the two runs show in general similar pattern of circulation cells of North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW). The cell of NADW occupies upper 2000 m mainly in north of 10 degree South, but the cell of AABW extends up to 50 degree North from the Antarctic continent in the layer below the deeper part of the NADW, while covering up to the surface in the south of 60 degree South. Difference-field of streamfunction between the two runs shows two core-regions. One core is located in the deeper part of Southern Ocean (i.e., the depth range of 2500-4000 m), and the other in the upper part, 500-2000 m depths, in the Northern Hemisphere. Latitudinal ranges of the two cores are mainly from 30 to 60 degrees. For the present it is conjectured that the two cores in the Northern and Southern Hemispheres of the streamfunction-difference field would represent regional responses to ice sheet removals of Greenland and the Antarctica, respectively. That is, the NADW cell becomes strong, but the AABW cell becomes weak, when the ice sheets are removed. Though the state of oceanic stratification could be the main reason for the deeper presence of AABW cell, the physical mechanism and processes related to the difference field are still under investigation.
DE: 1626 Global climate models (3337, 4928)
DE: 4283 Water masses
DE: 4515 Deep recirculations
DE: 4928 Global climate models (1626, 3337)
DE: 4962 Thermohaline
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting