Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/tc-2017-2
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
31 Jan 2017
Review status
A revision of this discussion paper is under review for the journal The Cryosphere (TC).
Sea Ice Assimilation into a Coupled Ocean-Sea Ice Adjoint Model of the Arctic Ocean
Nikolay V. Koldunov1,2,3, Armin Köhl1, Nuno Serra1, and Detlef Stammer1 1Institut für Meereskunde, Centrum für Erdsystemforschung und Nachhaltigkeit, Universität Hamburg, Germany
2MARUM - Center for Marine Environmental Sciences, Bremen
3AWI - Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
Abstract. High-resolution satellite sea ice concentrations (SIC), together with several ocean parameters, are assimilated into a regional Arctic coupled ocean-sea ice model covering the period 2000–2008 using the adjoint method. There is substantial improvement in the representation of the SIC spatial distribution, in particular with respect to the position of the ice edge and to the concentrations in the central parts of the Arctic Ocean during summer months. Seasonal cycles of total Arctic sea ice area show an overall improvement. During summer months values of sea ice extent become underestimated, however, it is shown that this metric is not suitable to characterize the quality of the sea ice simulation, as the root-mean-square difference to the data is reduced in nearly all months and years. Along with the SIC the sea ice thickness fields also become closer to observations, providing added-value by the assimilation. Very sparse data in the Arctic ocean, corresponding to a very small contribution to the cost function, prevent sizable improvements of assimilated ocean variables, with the exception of the sea surface temperature. The bias between simulated and observed SIC decreases mainly due to corrections to the surface atmospheric temperature, while contributions of other control variables remain small.

Citation: Koldunov, N. V., Köhl, A., Serra, N., and Stammer, D.: Sea Ice Assimilation into a Coupled Ocean-Sea Ice Adjoint Model of the Arctic Ocean, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-2, in review, 2017.
Nikolay V. Koldunov et al.
Nikolay V. Koldunov et al.
Nikolay V. Koldunov et al.

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Short summary
The manuscript describe one of the first attempts to use so called adjoint data assimilation method to bring Arctic Ocean model simulations closer to observation, especially in terms of the sea ice. It is shown that after assimilation the model bias in simulating the Arctic sea ice is considerably reduced. There is also additional improvement in the sea ice thickens representation, that is not assimilated directly.
The manuscript describe one of the first attempts to use so called adjoint data assimilation...
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