Southern Greenland precipitation d2H during interglacials of the past 500,000 years inferred from terrestrial leaf wax biomarkers preserved in Eirik Drift sediments
Abstract
Significant uncertainties remain in projections of future Greenland Ice Sheet (GrIS) behavior, including its likelihood of crossing destabilizing climate/ice-stability thresholds, stemming in part from a lack of constraints on long-term terrestrial climate forcing. Geologic evidence suggests that the GrIS may have transgressed climate/ice-stability thresholds to the point of substantial collapse on multiple occasions through the Quaternary, perhaps most recently during MIS 11 (424-374 thousand years B.P.). While MIS 11 was the most recent of several 'super-interglacials' identified in Siberian lake sediments, whether MIS 11 was a period of anomalous relative interglacial warmth in the western Arctic remains unknown. Here, we analyze the stable hydrogen isotopic composition (δ2H) of long-chain sedimentary n-alkanoic acids as a proxy for southern Greenland precipitation δ2H during previous interglacials, from sediments collected at ODP site 646 (58.21°N, 48.37°W, depth 3460 m) on the Eirik Drift approximately 280 km south of Greenland. Long- and short-chain n-alkanoic acid concentrations generally peak during interglacials, indicating increases in proximal terrestrial and marine primary productivity. Increases in productivity agree with trends in pollen and dinocycst concentrations from the same site. Preliminary results suggest that anomalous 2H-enriched precipitation over southern Greenland did not occur during MIS 11, relative to other interglacials of the last 500,000 years. Rather, the Last Interglacial, MIS 5e, demonstrates the least negative δ2H values, potentially suggesting greatest relative warmth. However, strong variations in δ2H within interglacials (>100‰) exceed the range expected from temperature-controlled fractionation, implicating changes in moisture source area or atmospheric dynamics as important controls on southern Greenland precipitation δ2H. These preliminary results support the notion that long duration rather than exceptional magnitude during MIS 11 may have driven substantial GrIS deglaciation, and suggest that "super interglacial" warmth was not expressed uniformly across the Arctic.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP41B1548C
- Keywords:
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- 0424 Biosignatures and proxies;
- BIOGEOSCIENCES;
- 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCES