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Radiocarbon andstable isotopeconstraints on LastGlacial Maximum andYounger Dryasventilation in thewestern NorthAtlantic Lloyd D Keigwin2004 год

Radiocarbon and stable isotope constraints on Last Glacial Maximum and Younger Dryas ventilation in the western North Atlantic
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Аннотация: Foraminiferal abundance, 14 C ventilation ages, and stable isotope ratios in cores from high deposition rate locations in the western subtropical North Atlantic are used to infer changes in ocean and climate during the Younger Dryas (YD) and Last Glacial Maximum (LGM). The δ 18 O of the surface dwelling planktonic foram Globigerinoides ruber records the present‐day decrease in surface temperature (SST) of ∼4°C from Gulf Stream waters to the northeastern Bermuda Rise. If during the LGM the modern δ 18 O/salinity relationship was maintained, this SST contrast was reduced to 2°C. With LGM to interglacial δ 18 O changes of at least 2.2‰, SSTs in the western subtropical gyre may have been as much as 5°C colder. Above ∼2.3 km, glacial δ 13 C was higher than today, consistent with nutrient‐depleted (younger) bottom waters, as identified previously. Below that, δ 13 C decreased continually to −0.5‰, about equal to the lowest LGM δ 13 C in the North Pacific Ocean. Seven pairs of benthic and planktonic foraminiferal 14 C dates from cores >2.5 km deep differ by 1100 ± 340 years, with a maximum apparent ventilation age of ∼1500 years at 4250 m and at ∼4700 m. Apparent ventilation ages are presently unavailable for the LGM < 2.5 km because of problems with reworking on the continental slope when sea level was low. Because LGM δ 13 C is about the same in the deep North Atlantic and the deep North Pacific, and because the oldest apparent ventilation ages in the LGM North Atlantic are the same as the North Pacific today, it is possible that the same water mass, probably of southern origin, flowed deep within each basin during the LGM. Very early in the YD, dated here at 11.25 ± 0.25 (n = 10) conventional 14 C kyr BP (equal to 12.9 calendar kyr BP), apparent ventilation ages <2.3 km water depth were about the same as North Atlantic Deep Water today. Below ∼2.3 km, four YD pairs average 1030 ± 400 years. The oldest apparent ventilation age for the YD is 1600 years at 4250 m. This strong contrast in ventilation, which indicates a front between water masses of very different origin, is similar to glacial profiles of nutrient‐like proxies. This suggests that the LGM and YD modes of ocean circulation were the same.
Год издания: 2004
Авторы: Lloyd D Keigwin
Издательство: American Geophysical Union
Источник: Paleoceanography
Ключевые слова: Geology and Paleoclimatology Research, Isotope Analysis in Ecology, Geological formations and processes
Другие ссылки: Paleoceanography (PDF)
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Open Access Server of the Woods Hole Scientific Community (Woods Hole Scientific Community) (PDF)
Open Access Server of the Woods Hole Scientific Community (Woods Hole Scientific Community) (HTML)