Quaternary North Atlantic Surface Paleoceanography in Regions of Potential Deep-Water Formation 
William F. Ruddiman 
Lamont-Doherty Geological Observatory 
Palisades, New York 10964 
At the time scale of the Quaternary climatic cycles, the sites of formation of North 
Atlantic Deep Water are not known. The interglacial extreme is presumably exemplified by the 
modern regions: the Norwegian, Greenland and Labrador Seas. During the major glacial-age 
coolings in the North Atlantic, the sites may have shifted well to the south, perhaps as far as 
the limit of the polar front at 40° to 50°N. Still other sites may have been important during 
intermediate climatic conditions. Because of the close coupling of high-latitude surface waters 
to North Atlantic Deep Water in the modern ocean (Swift, this volume), the history of sea- 
surface temperature (SST) oscillations across the high-latitude North Atlantic is relevant to an 
understanding of deep-water formation on the longer time scales. 
The history of the North Atlantic SST changes has been summarized by Ruddiman and 
McIntyre (1984) and is portrayed schematically in Figure 1. At these time scales, the SST 
records in all areas are dominated by fluctuations at the orbital periodicities of 100,000 to 
41,000 and 23,000 years. North of 55°N, in the regions of modern deep-water formation, extre- 
mely cold temperatures persist for very long intervals that are broken only by the minor war- 
mings associated with brief (10,000-year) interglaciations roughly every 100,000 years (Kellogg, 
1976). Between 55°N and 45°N, the dominant 100,000-year periodicity is joined by a strong 
41,000-year rhythm, and the combined signal from both periods marks the advances and retreats 
of the polar front. Between 45°N and 35°N, the 41,000-year periodicity disappears, and the 
still-strong 100,000-year cycle is slightly eclipsed by a remarkably strong signal at the 
23,000-year period. South of 35°N, the SST changes are much smaller near the stable center of 
the subtropical gyre (Crowley, 1981). 
Several lines of evidence suggest that these surface signals from the North Atlantic appear 
in geochemical tracers of Quaternary deep-water change. Mix and Fairbanks (this volume) show 
that the 41,000-year SST signal prominent in the polar front migrations also appears in the 13¢ 
record of benthic foraminifera. Boyle (1984) found a 41,000-year signal in cadmium gradients 
measured in benthic foraminifera from the South Atlantic. Mix and Fairbanks (in press) also 
have evidence of the 23,000-year signal in other isotopic tracers. In all cases, these signals 
are in phase with the North Atlantic SST signals at the comparable regions. The mechanism 
linking these deep-water responses to the long-term surface-water changes in not yet clear. 
Total IOO,000 YR 
ics-fae so Sian 
SSTw 23,000 YRB41,000 YR 
oa SST Signo! SS], Signal 
0 10 20 30 40 50 60 70 80 90 
Lat °N 
Figure 1. Maximum observed glacial-interglacial difference in estimated summer sea surface tem- 
perature versus latitude in the North Atlantic. Dashed portion of curve south of 40°N based on 
cores reported in Crowley (1981); portion north of 62°N based on cores from Kellogg (1976). 
Regions of greatest strength of SST changes at the three orbital periods also indicated. 
