Climate: Long-Range Investigation, 

 Mapping, and Prediction (CLIMAP) Study 



CLIMAP research focuses on defining, describing, and 

 explaining climate changes over the last 700,000 years. An 

 accurate definition of climatic change over this time scale is 

 needed to better understand the transition between what are 

 considered the two stable states of global climate — the ice 

 age and the temperate age. Knowledge about the mechanisms 

 of climatic change can be gained by comparing an accurate 

 description of this climatic transition with that predicted by 

 models of global climate. 



CLIMAP seeks answers to such basic questions as whether 

 changes in climate are caused by fluctuations in solar radiation 

 or by changes in the Earth's hydrosphere. Deep-sea sediments 

 provide the necessary chronological record for the study. The 

 sediment cores preserved in marine geological archives and 

 recent advances in age-dating techniques, automated analyses 

 of individual sediment cores, and computer correlation of the 

 many features in sediment strata make it possible to summarize 

 past sea surface conditions quantitatively. 



During the past year, the major accomplishment of the 

 CLIMAP Project was a first estimate of the sea surface tem- 

 perature for the world ocean during the last ice age (fig. 16). 

 This map provides the input needed to reconstruct the climate 

 of the world during the last ice age (18,000 years ago), using 

 two numerical models. 



The thermal response of the sea surface 18,000 years ago, 

 as compared with today's seasonal range, is similar in both 

 magnitude and geographic pattern. Seasonal changes in some 

 mid-latitude regions reach and sometimes exceed 10°C. Except 

 where upwelling occurs, low-latitude changes are about 2°C, 

 and some subtropical areas show no change. Other anomalous 

 features are: 



1) Marked equatorward displacement of polar fronts 

 in North Atlantic and Southern Ocean, but not in 

 North Pacific; 



2) Areal expansion of subpolar waters in all oceans; 



3) Stable geometry of subtropical gyres in all oceans; 



4) Steepened thermal gradients across polar fronts, 

 apparently marking the axis of ice-age westerlies 

 in both hemispheres; and 



5) Increase in extent of sea ice — during all seasons 

 in North Atlantic, and especially during austral 

 summer in Southern Ocean. 



Maps have been completed showing the distribution of 

 carbonate, organic carbon, opal, and quartz concentrations 

 in surface sediments of the North Pacific for 600,000 and 

 700,000 years ago. A zonal band of high quartz values was 

 found to shift southward during glacial times. Also completed 

 are time series analyses of carbonate and opal accumulation 



Figure 16. — World sea surface temperature (°C) 18,000 years ago. 



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