Patterson, S. L., and H. A. Sievers. 



1976. Contributions of AGS Yelcho to FDRAKE, 1976. 

 Antarc. J. U.S. X: 158-159. 



Treshnikov, A. F., R. D. Pillsbury, W. D. Nowlin, Jr., E. I. 

 Sarukhanyan, and N. P. Smirnov. 



1977. A comparison of summer current measurements in the 

 Drake Passage. J. Phys. Oceanogr. 7:610-614. 



Climate: Long-Range Investigation, Mapping, 

 and Prediction (CLIMAP) Study 



CLIMAP research is designed to describe and explain the 

 major changes in global climate that have occurred in the past 

 million years. These changes involve transitions between two 

 partly stable states of global climate — ice ages and temperate 

 (interglacial) periods. The fundamental objective is to improve 

 our understanding of the causes of long-term climatic change. 

 Previous CLIMAP work has firmly established a concept sug- 

 gested by earlier workers that variation in the Earth-Sun orbital 

 geometry is the pacemaker of long-term climatic change. Much 

 of current CLIMAP work is directed toward studies of the 

 interaction of the various parts of the global climate system. 

 Ocean sediment cores are multichannel recorders of changes in 

 the ocean circulation, variation in the size of ice sheets, and 

 changes in terrestrial climate. Knowledge of how these parts 

 of the global system have interacted in the past provides in- 

 sight into some of the causal relationships that will determine 

 the climate of the future. These long-range trends are the 

 fundamental, large-amplitude rhythms that underlie the higher 

 frequency and smaller scale variations of recent centuries. 



NSF's Climate Dynamics Research Section and the IDOE 

 Section jointly fund CLIMAP studies. CLIMAP scientists are 

 listed in table 8, and CLIMAP task groups in table 9. 



Investigation of the Last Interglacial Period 



The year 1977 has been one of transition for CLIMAP. With 

 the data-gathering and synthesizing effort for the 18,000 before 

 present (B.P.) ice-age maximum experiment ended, CLIMAP 

 has begun a major new project to reconstruct the climate of the 

 last interglacial period. Its purpose is to make a global study of 

 the sequence of climatic events that occur when climate changes 

 from a time of maximum global ice volume through an ice- 

 volume minimum (the interglacial) and back to conditions of 

 re-expanded global ice. Because we live today in an interglacial 

 climate, this experiment should increase our understanding of 

 the changes toward glacial climates expected in the future. 



The project has two major parts. First, CLIMAP scientists 

 will construct a map of the Earth's surface at the time of mini- 

 mum global ice extent, 125,000 years ago, for comparison with 



the Earth's surface today. The second part focuses on leads and 

 lags between various parts of the climate system as the Earth 

 goes into and comes out of an interglacial period. Two pre- 

 liminary examples of these lead/lag relationships shown in 

 figure 30 indicate that in certain parts of the world (notably the 

 subantarctic) sea-surface temperatures warmed before land ice 

 began to melt and cooled before land ice again began to grow. 

 In other areas (the subpolar North Atlantic), the opposite is 

 true. Thus changes in the ocean temperatures of the high- 

 latitude oceans of the Southern Hemisphere lead the ice-volume 

 variations and significantly lead the changes in high-latitude 

 Northern Hemisphere oceans. 



Spectral Investigations of Long Periods 



One major advance in CLIMAP research this year was the 

 publication of additional documentation of the influence of the 

 Earth's orbital geometry on climate. Adding to earlier work 

 from Indian Ocean subantarctic cores, CLIMAP researchers 

 found in both the Atlantic and Pacific Oceans clear evidence 

 of a concentration of spectral power at the three orbital fre- 

 quencies (100,000 years, 43,000 years, and 22,000 years). (See 

 fig. 31.) In addition, cross-spectral analysis of isotopic and 

 chemical data indicates that changes in global ice volume led 

 variations in carbonate preservation in the equatorial Pacific 

 cores by several thousand years (fig. 32). 



Spectral Analysis of Short Periods 



The varved sediments of the Santa Barbara Basin offer a 

 unique opportunity to study the changes in oceanographic 

 conditions there during the last 8,000 years. Analysis of the 

 radiolaria found in a varved sediment core from the Santa 

 Barbara Basin yields an 8,000-year continuous record sampled 

 every 25 years. 



Past sea-surface temperatures were calculated from the radio- 

 larian fauna (fig. 33). Results indicate that intervals from 800 

 to 1,800, 3,600 to 3,800, and 5,400 to 8,000 years B.P. were 

 warmer than today. The warm interval from 5,400 to 8,000 

 B.P. is a time when pollen analysis indicates a more humid 

 environment for southern California, a condition consistent with 

 warmer sea-surface temperatures. The spectra of the sea-surface 

 temperature record for the Santa Barbara Basin shows that the 

 fluctuations are not random, with much of the variance in the 

 record explained by low-frequency components (fig. 34). 



The 18,000 B.P. Experiment 



The global map of the ice-age world has been completed. 

 The analytical and stratigraphic error of each transfer-function 

 estimate of sea-surface temperature was categorized and docu- 

 mented for all 245 cores used in the ice-age reconstruction. 

 Digitized maps of the final reconstruction were delivered to sev- 

 eral general circulation modelers for simulation experiments 

 during the next year. 



Changes in the Antarctic Ocean 



The Antarctic Task Group has investigated changes in sea ice 

 cover around the Antarctic Continent between the last glacial 

 period and today. The results indicate that ice in the Antarctic 

 Sea was then much more extensive in the winter than today 

 (40 million km 2 vs. 20 million km 2 today). (See fig. 35.) 



45 



