Using Cosmogenic Nuclides in Ice-Rafted Debris to Constrain Ice Sheet Dynamics Associated with Heinrich Events
Abstract
Heinrich events - periodic discharges of iceberg armadas expelled from the Laurentide Ice Sheet every 7,000 to 12,000 years during the last glacial period - provide an outstanding opportunity to explore ice sheet dynamics associated with abrupt climate change. Nonetheless, the underlying mechanisms behind Heinrich events remain unclear. We are measuring cosmogenic nuclide (10Be, 26Al, 14C) concentrations in North Atlantic ice-rafted debris deposited before, during, and after the six most recent Heinrich events to better constrain the associated subglacial sediment sourcing and erosional intensity.
Because cosmogenic nuclides accumulate in land surfaces exposed to cosmic rays, but decrease in concentration when surfaces are ice covered due to radioactive decay and erosion, nuclide concentrations in ice-rafted debris reflect an integrated history of exposure and erosion along flow lines discharging icebergs to the ocean. The differential decay rates of these nuclides (10Be t1/2 = 1.4 Myr, 26Al 1/2 = 0.7 Myr, 14C 1/2 = 5.7 kyr) cause their ratios to decrease below production values during burial, providing information about the duration of ice cover in sediment source regions. Comparing nuclide concentrations and ratios between Heinrich and non-Heinrich intervals may help reveal how ice sheet rates and patterns of erosion, as well as exposure, varied across these singular events.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP31C1646L
- Keywords:
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- 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions;
- GEODESY AND GRAVITY;
- 1621 Cryospheric change;
- GLOBAL CHANGE;
- 1641 Sea level change;
- GLOBAL CHANGE