9416735 Fisher This project involves researchers from Woods Hole Oceanographic Institution and Indiana University. They will analyse temperature and thermal conductivity measurements of sediments at two sites drilled on the eastern U.S. continental slope by the Ocean Drilling Program (ODP). The will also carry out instrument calibrations which will allow future collection of such data at drilling sites of opportunity. The objective of the research is to examine ocean temperature change, particularly in "intermediate" water depths, which is important in understanding global climate change over the past few thousand years. The data in hand was collected at two ODP sites located only 4.4 kilometers apart near the edge of the Gulf Stream off New Jersey. The two temperature profiles show a dramatic difference in the upper sediment temperature gradient, and the investigators have modelled the data, suggesting that a plausible interpretation is that the position of the Gulf Stream has changed measurably over the past 100 to 130 years, affecting the shallower site but not the deeper one. Their observations are consistent with a 5-7 degree (Celsius) temperature change over that time period at the shallower site, in about 440 meters water depth. Such large temperature change is not commonly observed at these depths. The research carried out under this award will allow them to extend their modelling to examine both the hypothesis they propose (changes in Gulf Stream location) as well as other possible causes (subsurface aquifer flow, sediment slumping are examples) for the observed temperature and conductivity profiles. Data will be compared with historical measurements of water column temperature in the region, as well as with published "proxy" measurements of longer-term temperature which are obtained through analysis of isotopes of oxygen preserved in planktonic foraminifera skeletons. This award also provides funds to carry out a precise calibration of the instrumentation for measuring subs urface temperatures to remove uncertainties associated with instrument error in the future. ***
