Impact of millennial-scale oceanic variability on the Greenland ice-sheet evolution throughout the last glacial period
<p>Temperature reconstructions from Greenland ice-sheet (GrIS) ice cores indicate the occurrence of more than 20 abrupt warmings during the last glacial period (LGP) known as Dansgaard-Oeschger (D-O) events. Although their ultimate cause is still debated, evidence from both proxy data and mode...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-03-01
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| Series: | Climate of the Past |
| Online Access: | https://www.clim-past.net/15/593/2019/cp-15-593-2019.pdf |
| Summary: | <p>Temperature reconstructions from Greenland ice-sheet (GrIS) ice
cores indicate the occurrence of more than 20 abrupt warmings during the
last glacial period (LGP) known as Dansgaard-Oeschger (D-O) events. Although
their ultimate cause is still debated, evidence from both proxy data and
modelling studies robustly links these to reorganisations of the Atlantic
Meridional Overturning Circulation (AMOC). During the LGP, the GrIS expanded
as far as the continental shelf break and was thus more directly exposed to
oceanic changes than in the present. Therefore oceanic temperature
fluctuations on millennial timescales could have had a non-negligible impact
on the GrIS. Here we assess the effect of millennial-scale oceanic
variability on the GrIS evolution from the last interglacial to the present
day. To do so, we use a three-dimensional hybrid ice-sheet–shelf model forced
by subsurface oceanic temperature fluctuations, assumed to increase during
D-O stadials and decrease during D-O interstadials. Since in our model the
atmospheric forcing follows orbital variations only, the increase in total
melting at millennial timescales is a direct result of an increase in basal
melting. We show that the GrIS evolution during the LGP could have been
strongly influenced by oceanic changes on millennial timescales, leading to
oceanically induced ice-volume contributions above 1 m sea level equivalent (SLE). Also, our results
suggest that the increased flux of GrIS icebergs as inferred from North
Atlantic proxy records could have been triggered, or intensified, by peaks in
melting at the base of the ice shelves resulting from increasing subsurface
oceanic temperatures during D-O stadials. Several regions across the GrIS
could thus have been responsible for ice mass discharge during D-O events,
opening the possibility of a non-negligible role of the GrIS in oceanic
reorganisations throughout the LGP.</p> |
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| ISSN: | 1814-9324 1814-9332 |