RECONSTRUCTION OF TERRESTRIAL AND MARINE CLIMATE FROM SOUTHERN GREENLAND DURING THE PLEISTOCENE

The Arctic region is experiencing ongoing rising temperatures at levels higher than the global average. Increasing atmospheric and ocean temperatures will impact the melting rate of the Greenland Ice Sheet. To better understand future changes in this region we look to sedimentary records with material from the southern Labrador Sea to assess changes in ocean currents, sea surface temperatures, and atmospheric temperatures. Here we compiled both a terrestrial and marine record from a North Atlantic Ocean Drilling Program (ODP) legacy core from Site 647 between Labrador and southwestern Greenland. Site 647 captures the Pleistocene (2.5 Ma to 200 kyr), a time period where the Greenland Ice Sheet underwent partial deglaciation likely during known super interglacials, although pCO₂ was similar to today. Organic compounds including leaf waxes and branched glycerol dialkyl glycerol tetraethers (brGDGTs) were used to assess changes in the terrestrial environment, likely sourced from Nova Scotia, Canada or transported via the St. Lawrence Seaway. Mean annual air temperature was calculated from branched glycerol dialkyl glycerol tetraethers (brGDGTs) using the MBT´_5Me with values ranging from 6° to 12°C. The combination of these proxies with previous pollen work suggests decreasing temperatures and more sparse vegetation from the early to late Pleistocene. Multiple sea surface temperature (SST) records were generated from the isoprenoid GDGTs (isoGDGTs) using the TEX₈₆ index, hydroxylated GDGTs (OH-GDGTs), alkenones using the U^Kˈ₃₇ index, and the long chain diol index to identify a reliable SST reconstruction for the North Atlantic. The TEX₈₆ GDGT reconstructions estimated SSTs from 2° to 12°C. In addition, diol proxies such as the diol index 1 and the FC32 1,15 were utilized to evaluate upwelling and freshwater inputs to the site, respectively. These results were combined with planktic foraminiferal species assemblages to assess glacial-interglacial shifts in currents of the subpolar gyre northwest of the North Atlantic Drift. The combination of proxies identified periods of cooler and warmer temperatures associated with an increase in upwelling and a decrease in freshwater inputs. Both the marine and terrestrial records add new data to a region and time period with sparse records.