Postglacial marine diatom record of the Palmer Deep, Antarctic Peninsula (ODP Leg 178, Site 1098) 1. Total diatom abundance

Late Pleistocene to Holocene climate variability in the Antarctic Peninsula is described from Ocean Drilling Program (ODP) Leg 178 Site 1098 (Palmer Deep) using total diatom abundance (valves per gram dry sediment) as a paleoproductivity proxy. Diatom frustules are absent in the diamicton at the base of the core, which was deposited prior to age calibrated circa 13.2 ka. Immediately above, the diamicton frustules are in low abundance as rare fragments and become increasingly more abundant and well preserved up core. A rapid and major increase in productivity after circa 12.8 ka is evident from distinctly laminated sediments that overlie the diamicton. The strongly laminated section was deposited during a “deglaciation phase” that followed the retreat of grounded ice after the Last Glacial Maximum. Diatom productivity decreased during a climatic cooling and/or change in meltwater supply, until circa 9.0 ka. Between 9.0 and 4.4 ka, productivity increased steadily again, with diatom abundance maxima reached during a mid‐Holocene “climatic optimum.” The optimum is interrupted by a brief cold event of ∼1000 years duration 6.0–5.0 ka. After 4.4 ka, productivity generally decreased, and the last 500 years have experienced the lowest diatom productivity of the postglacial period. The Palmer Deep sediment is compared to ice core and lake sediment records from other regions around the Antarctic Peninsula. These diverse data sets confirm that the Antarctic Peninsula has been a region of rapid and variable climate fluctuation since the Last Glacial Maximum.