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abstracts
Glacial seasonal-resolution sea surface temperature records from paired δ18O and Mg/Ca in limpet shells from Gibraltar
Julie Ferguson, Gideon Henderson, Darren Fa, Clive Finlayson
Seasonal resolution climate records from higher latitudes are important to allow investigation of the role of seasonality in controlling mean climate on diverse timescales, and of the evolution of climate systems such as the North Atlantic Oscillation. However, outside the range of tropical corals, very few seasonal-resolution sea surface temperature (SST) records exist for the Holocene and none for the last glacial. Paired δ18O and Mg/Ca analyses of micromilled samples of modern limpet (Patella) shells from Gibraltar allow the reconstruction of average seawater δ18O and capture over 80% of the weekly range in SST. Glacial-interglacial sea-level changes make long time-series of intertidal molluscs difficult to find. On Gibraltar, Neanderthals and early humans collected molluscs for food and transported them inland to caves such as Gorham’s Cave at times throughout the last 110 thousand years. Applying Mg/Ca and δ18O to radiocarbon-dated examples of limpet shells from such caves provide the first seasonal-resolution SST and seawater δ18O records for the last glacial outside the tropics. Results show that SST seasonality is variable through the last glacial but is greater than today by an average of 2oC even at the last glacial maximum when seasonal ranges of local insolation were similar to today. This implies that regional climate feedbacks rather than insolation are controlling SST seasonality and suggests that the presence of Northern Hemisphere ice sheets during the last glacial resulted in greater winter cooling and greater SST seasonality. These results contrast with GCM model estimates of SST values and seasonality during the glacial.
Julie Ferguson, Department of Earth System Science, University of California, Irvine,Croul Hall, Irvine, CA, 92697, United States, julie.ferguson@uci.edu
Gideon Henderson, University of Oxford, United Kingdom
Darren Fa, The Gibraltar Museum, Gibraltar
Clive Finlayson, The Gibraltar Museum, Gibraltar
Session: CCT2: Proxy Development, Calibration and Validation
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