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NEMO–ICB (v1.0): interactive icebergs in the NEMO ocean model globally configured at eddy-permitting resolution

NEMO–ICB (v1.0): interactive icebergs in the NEMO ocean model globally configured at eddy-permitting resolution
NEMO–ICB (v1.0): interactive icebergs in the NEMO ocean model globally configured at eddy-permitting resolution
An established iceberg module, ICB, is used interactively with the Nucleus for European Modelling of the Ocean (NEMO) ocean model in a new implementation, NEMO–ICB (v1.0). A 30-year hindcast (1976–2005) simulation with an eddy-permitting (0.25°) global configuration of NEMO–ICB is undertaken to evaluate the influence of icebergs on sea ice, hydrography, mixed layer depths (MLDs), and ocean currents, through comparison with a control simulation in which the equivalent iceberg mass flux is applied as coastal runoff, a common forcing in ocean models. In the Southern Hemisphere (SH), drift and melting of icebergs are in balance after around 5 years, whereas the equilibration timescale for the Northern Hemisphere (NH) is 15–20 years. Iceberg drift patterns, and Southern Ocean iceberg mass, compare favourably with available observations. Freshwater forcing due to iceberg melting is most pronounced very locally, in the coastal zone around much of Antarctica, where it often exceeds in magnitude and opposes the negative freshwater fluxes associated with sea ice freezing. However, at most locations in the polar Southern Ocean, the annual-mean freshwater flux due to icebergs, if present, is typically an order of magnitude smaller than the contribution of sea ice melting and precipitation. A notable exception is the southwest Atlantic sector of the Southern Ocean, where iceberg melting reaches around 50% of net precipitation over a large area. Including icebergs in place of coastal runoff, sea ice concentration and thickness are notably decreased at most locations around Antarctica, by up to ~ 20% in the eastern Weddell Sea, with more limited increases, of up to ~ 10% in the Bellingshausen Sea. Antarctic sea ice mass decreases by 2.9%, overall. As a consequence of changes in net freshwater forcing and sea ice, salinity and temperature distributions are also substantially altered. Surface salinity increases by ~ 0.1 psu around much of Antarctica, due to suppressed coastal runoff, with extensive freshening at depth, extending to the greatest depths in the polar Southern Ocean where discernible effects on both salinity and temperature reach 2500 m in the Weddell Sea by the last pentad of the simulation. Substantial physical and dynamical responses to icebergs, throughout the global ocean, are explained by rapid propagation of density anomalies from high-to-low latitudes. Complementary to the baseline model used here, three prototype modifications to NEMO–ICB are also introduced and discussed.
1991-9603
1547-1562
Marsh, R.
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Ivchenko, V.O.
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Skliris, N.
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Alderson, S.
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Bigg, G.R.
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Madec, G.
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Blaker, A.T.
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Aksenov, Y.
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Sinha, B.
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Coward, A.C.
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Le Sommer, J.
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Merino, N.
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Zalesny, V.B.
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Marsh, R.
702c2e7e-ac19-4019-abd9-a8614ab27717
Ivchenko, V.O.
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Skliris, N.
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Alderson, S.
00ee9859-a11f-4040-a963-d88d4ae2740d
Bigg, G.R.
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Madec, G.
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Blaker, A.T.
94efe8b2-c744-4e90-87d7-db19ffa41200
Aksenov, Y.
1d277047-06f6-4893-8bcf-c2817a9c848e
Sinha, B.
544b5a07-3d74-464b-9470-a68c69bd722e
Coward, A.C.
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Le Sommer, J.
b2f7856c-9030-4d9e-bda6-dbfea753d329
Merino, N.
c79253ef-6920-4b65-87de-d8f9bb6b0821
Zalesny, V.B.
f498beb9-4ac3-410e-b563-0deeeb1f8e9e

Marsh, R., Ivchenko, V.O., Skliris, N., Alderson, S., Bigg, G.R., Madec, G., Blaker, A.T., Aksenov, Y., Sinha, B., Coward, A.C., Le Sommer, J., Merino, N. and Zalesny, V.B. (2015) NEMO–ICB (v1.0): interactive icebergs in the NEMO ocean model globally configured at eddy-permitting resolution. Geoscientific Model Development, 8 (5), 1547-1562. (doi:10.5194/gmd-8-1547-2015).

Record type: Article

Abstract

An established iceberg module, ICB, is used interactively with the Nucleus for European Modelling of the Ocean (NEMO) ocean model in a new implementation, NEMO–ICB (v1.0). A 30-year hindcast (1976–2005) simulation with an eddy-permitting (0.25°) global configuration of NEMO–ICB is undertaken to evaluate the influence of icebergs on sea ice, hydrography, mixed layer depths (MLDs), and ocean currents, through comparison with a control simulation in which the equivalent iceberg mass flux is applied as coastal runoff, a common forcing in ocean models. In the Southern Hemisphere (SH), drift and melting of icebergs are in balance after around 5 years, whereas the equilibration timescale for the Northern Hemisphere (NH) is 15–20 years. Iceberg drift patterns, and Southern Ocean iceberg mass, compare favourably with available observations. Freshwater forcing due to iceberg melting is most pronounced very locally, in the coastal zone around much of Antarctica, where it often exceeds in magnitude and opposes the negative freshwater fluxes associated with sea ice freezing. However, at most locations in the polar Southern Ocean, the annual-mean freshwater flux due to icebergs, if present, is typically an order of magnitude smaller than the contribution of sea ice melting and precipitation. A notable exception is the southwest Atlantic sector of the Southern Ocean, where iceberg melting reaches around 50% of net precipitation over a large area. Including icebergs in place of coastal runoff, sea ice concentration and thickness are notably decreased at most locations around Antarctica, by up to ~ 20% in the eastern Weddell Sea, with more limited increases, of up to ~ 10% in the Bellingshausen Sea. Antarctic sea ice mass decreases by 2.9%, overall. As a consequence of changes in net freshwater forcing and sea ice, salinity and temperature distributions are also substantially altered. Surface salinity increases by ~ 0.1 psu around much of Antarctica, due to suppressed coastal runoff, with extensive freshening at depth, extending to the greatest depths in the polar Southern Ocean where discernible effects on both salinity and temperature reach 2500 m in the Weddell Sea by the last pentad of the simulation. Substantial physical and dynamical responses to icebergs, throughout the global ocean, are explained by rapid propagation of density anomalies from high-to-low latitudes. Complementary to the baseline model used here, three prototype modifications to NEMO–ICB are also introduced and discussed.

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Published date: 27 May 2015
Organisations: Marine Systems Modelling, Physical Oceanography

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Local EPrints ID: 385057
URI: http://eprints.soton.ac.uk/id/eprint/385057
ISSN: 1991-9603
PURE UUID: 41225bf9-6a6b-4436-9423-cf2bfd438329
ORCID for N. Skliris: ORCID iD orcid.org/0000-0002-2473-2586

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Date deposited: 15 Dec 2015 09:53
Last modified: 15 Mar 2024 03:39

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Contributors

Author: R. Marsh
Author: V.O. Ivchenko
Author: N. Skliris ORCID iD
Author: S. Alderson
Author: G.R. Bigg
Author: G. Madec
Author: A.T. Blaker
Author: Y. Aksenov
Author: B. Sinha
Author: A.C. Coward
Author: J. Le Sommer
Author: N. Merino
Author: V.B. Zalesny

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