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Images: Ground-Truthing the Paleoclimate Record

Research Associate Dorinda Ostermann removes sample cups from a sediment trap recovered aboard the Icelandic Research Vessel Bjarni S?mundsson.

Distribution maps and scanning electron microscope images for three foraminifers. The height of each bar indicates the relative abundance of the species as a percent of the total foraminifer assemblege. N. pachyderma (left coiling) on the top prefers water colder than 8 degrees centigrade. G. bulloides in the middle prefers waters that are influenced by the Gulf Stream. G. ruber at the bottom figure prefers warm central North Atlantic water.

All biogenic particles arriving on the ocean floor carry a memory imprint of their growth environment. Fossil shells of foraminifera contain many clues to the past oceanic environment, including temperature and salinity information. The chart above shows the range of sea surface temperatures sampled by WHOI time-series sediment traps around the world from less than 2°C to greater than 32°C.The world map below indicates the locations of these sediment traps.

Distribution of G. ruber (percent of total foraminifer population) based upon temperature of surface water obtained by Satellite data. The open circles are from the JGOFS 47 N sediment trap; closed circles are from the JGOFS 34 N sediment.

Distribution of G. bulloides (percent of total foraminifer population) based upon temperature of surface water obtained by satellite data. The open circles are from the JGOFS 47°N sediment trap; closed circles are from the JGOFS 34°N sediment.

The top panel shows distribution of Neogloboquadrina pachyderma (left coiling) as a percent of total foraminifer population based on surface water temperature obtained from satellite data. Abundances of this species increase in water below 8°C. The lower panel shows an abrupt change in N. pachyderma coiling direction from left to right when the surface water warms above 8°C.

Air temperature over Greenland (based on ice core isotopic measurements) and sea surface variability in the North Atlantic (based on left-coiling N. pachyderma percentages). The covariation of the records implies that variations in the circulation of the North Atlantic are strongly linked to temperatures in the region.