Abstract A multicore from Emerald Basin, on the conti-nental margin off Nova Scotia, has a modern 14C age at the top, and other 14C dates indicate a linear sedimenta-tion rate of 30 cm/ka to 1600 calendar years BP. This rate is great enough to record century-to-millennial scale changes in the surfac...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.594.7207 http://faculty.washington.edu/jsachs/lab/www/Keigwin-EB_SST_2ka-ClimDyn03.pdf |
| Summary: | Abstract A multicore from Emerald Basin, on the conti-nental margin off Nova Scotia, has a modern 14C age at the top, and other 14C dates indicate a linear sedimenta-tion rate of 30 cm/ka to 1600 calendar years BP. This rate is great enough to record century-to-millennial scale changes in the surface and deep (250 m) waters in the basin that are influenced by the Labrador Current. We applied five proxies for seawater temperature changes to the sediments of Emerald Basin, including the percent abundance and the oxygen isotope ratio (d18O) of the polar planktonic foraminifer N. pachyderma (s.), the unsaturation ratio of alkenones (Uk¢37) produced by prymnesiophyte phytoplankton, and the d18O andMg/Ca of benthic foraminifera. All five proxies indicate the ocean warmed suddenly sometime in the past 150 years or so. The exact timing of this event is uncertain because 14C dating is inaccurate in recent centuries, but this abrupt warming probably correlates with widespread evidence for warming in the Arctic in the nineteenth century. Because the Canadian Archipelago is one of the twomain sources for the Labrador Current, warming and melting of ice caps in that region may have affected Labrador Current properties. Before this recent warming, sea surface temperature was continually lower by 1–2 C, and bottomwater was colder by about 6 C in Emerald Basin. These results suggest that there was no Medieval Warm Period in the coastal waters off Nova Scotia. Because there is also no evidence of medieval warming in the Canadian archipelago, it seems likely that coastal waters from Baffin Bay to at least as far south as Nova Scotia were continually cold for 1500 of the past 1600 years. 1 |
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