North Atlantic Holocene Paleoceanography and Millennial Climate Cycles., North Atlantic climate has varied on centennial to millennial time scales throughout the Holocene. To assess the magnitude and spatial pattern of sea surface temperature (SST) changes during the Holocene, I will calibrate planktonic foraminiferal Mg/Ca and generate down-core records at 40-60 year time resolution from 0-14000 BP., I. Measuring Mg/Ca in G. bulloides in down-core records, The open-chamber morphology and abundant ice-rafted detritus in the North Atlantic presents problems for effective cleaning of foraminifera for trace metal analysis. Using a combination of published cleaning procedures including reductive cleaning and manual silicate removal, picked sample reproducibility of <3% may be obtained.

II. Local calibration of Mg/Ca in G. bulloides and N. pachyderma (dextral), Seven core tops from the sub-polar North Atlantic were obtained with calibrated 14C ages indicating post 1950 (modern) core top ages. Mg/Ca and d18O will be measured in two common planktonic species to calibrate the Mg/Ca paleothermometer. This will represent the first core top Mg/Ca calibration from the North Atlantic to use verified modern tops.

III. Measuring Mg/Ca in G. bulloides in down-core records, Mg/Ca is sensitive to post-depositional dissolution from regeneration of organic matter in sediment cores. I will examine the sensitivity of Mg/Ca to dissolution on the long-term (Holocene) and on the millennial scale in two cores closely located but with different dissolution histories. Additionally, Mg/Ca will be measured in a high resolution (40-60 years) core from the eastern North Atlantic. This record will be compared with existing proxies for Holocene paleoclimate, such as ice-rafted petrologic tracers and foraminiferal assemblages.