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| Titel |
How do icebergs affect the Greenland ice sheet under pre-industrial conditions? – a model study with a fully coupled ice-sheet–climate model |
| VerfasserIn |
M. Bugelmayer, D. M. Roche, H. Renssen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 9, no. 3 ; Nr. 9, no. 3 (2015-05-04), S.821-835 |
| Datensatznummer |
250116787
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| Publikation (Nr.) |
 copernicus.org/tc-9-821-2015.pdf |
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| Zusammenfassung |
| Icebergs have a potential impact on climate since they release freshwater
over a widespread area and cool the ocean due to the take-up of latent
heat. Yet, so far, icebergs have never been modelled using an ice-sheet
model coupled to a global climate model. Thus, in climate models their
impact on climate has been restricted to the ocean. In this study, we
investigate the effect of icebergs on the climate of the mid- to high
latitudes and the Greenland ice sheet itself within a fully coupled ice-sheet
(GRenoble model for Ice Shelves and Land Ice, or GRISLI)–earth-system (iLOVECLIM) model set-up under pre-industrial
climate conditions. This set-up enables us to dynamically compute the
calving sites as well as the ice discharge and to close the water cycle
between the climate and the cryosphere model components. Further, we analyse
the different impact of moving icebergs compared to releasing the ice
discharge at the calving sites directly. We performed a suite of sensitivity
experiments to investigate the individual role of the different factors that
influence the impact of the ice release on the ocean: release of ice
discharge as icebergs versus as freshwater fluxes, and freshening and latent
heat effects. We find that icebergs enhance the sea-ice thickness around
Greenland, thereby cooling the atmosphere and increasing the Greenland ice
sheet's height. Melting the ice discharge directly at the calving sites,
thereby cooling and freshening the ocean locally, results in a similar
ice-sheet configuration and climate as the simulation where icebergs are
explicitly modelled. Yet, the simulation where the ice discharge is released
into the ocean at the calving sites while taking up the latent heat
homogeneously underestimates the cooling effect close to the ice-sheet
margin and overestimates it further away, thereby causing a reduced
ice-sheet thickness in southern Greenland. We conclude that in our fully coupled
atmosphere–ocean–cryosphere model set-up the spatial distribution of
the take-up of latent heat related to iceberg melting has a bigger impact on
the climate than the input of the iceberg's meltwater. Moreover, we find
that icebergs affect the ice sheet's geometry even under pre-industrial
equilibrium conditions due to their enhancing effect on sea ice, which
causes a colder prevailing climate. |
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