PRODUCTIVITY CYCLES OF 200-300 YEARS IN THE ANTARCTIC PENINSULA REGION - UNDERSTANDING LINKAGES AMONG THE SUN, ATMOSPHERE, OCEANS, SEA-ICE,AND BIOTA

Compared to the rest of the world's oceans, high-resolution late Holoc ene paleoclimatic data from the Southern Ocean are still rare. We pres ent a multiproxy record from a sediment core retrieved from a deep bas in on the western side of the Antarctic Peninsula that reveals a drama tic perspective on paleoclimatic changes over the past 3700 yr. Analys es completed include measurement of magnetic susceptibility and granul ometry, bed thickness, particle size, percent organic carbon, bulk den sity, and microscopic evaluation of diatom and benthic foraminiferal a ssemblages and abundances. Downcore variability of these parameters de monstrates the significance of both short-term cycles, which recur app roximately every 200 yr, and longer term events (approximate to 2500 y r cycles) that are most likely related to global climatic fluctuations . In the upper 600 cm of the core, lower values of magnetic susceptibi lity (MS) are correlated with lower bulk density, the presence of thin ly laminated units, specific diatom assemblages, and generally higher total organic carbon content. Below 600 cm, magnetic susceptibility is uniformly ion; though variability in other parameters continues, The magnetic susceptibility signal is controlled primarily by dilution of ferromagnetic phases with biosiliceous material. This signal may be en hanced further by dissolution of magnetite in the magnetic susceptibil ity lows (high total organic carbon). The role of variable primary pro ductivity and its relationship to paleoclimate is assessed through the diatom data,In particular, magnetic susceptibility lows are character ized by higher than normal abundances of Chaetoceros resting spores. C orethron criophilum and/or Rhizosolenia spp, also are found, as is a h igher ratio of the most common species of Fragilariopsis versus specie s of Thalassiosira., These assemblages are indicative of periods of hi gh primary productivity driven by the presence of a meltwater stabiliz ed water column, The 200 yr cyclicity noted in other paleoclimatic rec ords around the world suggests a global forcing mechanism, possibly so lar variability, In addition to the cyclic changes in productivity, ov erall elevated productivity is noted below 600 cm, or prior to ca, 250 0 yr B.P. This increased productivity may represent the tail end of a Holocene climatic optimum, which is widely recognized in other parts o f the world, but as yet is poorly documented in Antarctica.