Images: Sedimentary Record Yields Several Centuries of Data
Average summertime temperature over six centuries in the northern hemisphere. Note generally cooler temperatures between 1550 and 1900, the period known as the Little Ice Age (Data courtesy of Raymond S. Bradley, University of Massachusetts)
Shells of planktonic animals called formainifera record climatic conditions as they are formed. This one, Globigerinoides ruber, lives year-round at the surface of the Sargasso Sea. The form of the live animal is shown at right, and its shell, which is actually about the size of a fine grain of sand, at left.
Bermuda Station S hydrography shows the oxygen isotope ratio that a foram would have if it deposited its shell in equilibrium with the annual average sea surface temperature and salinity observed since 1954 at Station S near Bermuda. The large decrease in sea surface temperature and increase in salinity in the late 1960s was caused by unusually unpleasant weather those years. (Temperature and salinity data provided by Terry Joyce)
Since 1978, Scientist Emeritus Werner Deuser has collected a nearly continuous suite of deep sediment trap samples at the Ocean Flux Program site near Station S. The Ocean Flux Program traps are shown following recovery aboard the Bermuda Biological Station vessel Weatherbird II. The traps were deployed along a bottom tethered mooring at 500, 1,500 and 3,200 meters depths to intercept particles sinking through the water column. Deuser recently passed the leadership of the Bermuda time-series program on to Assistant Scientist Maureen Conte.
Estimated sea surface temperature from Station S annual averages and from Globigerinoides ruber shell oxygen isotopes averaged at 50-year intervals. Note that the range of sea surface temperature variability on longer time scales is much larger than what has been observed since 1954 at Station S.