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Whereas the atmospheric model covers the whole globe, the ocean model has the additional problem of lateral boundaries along coasts causing effects such as boundary currents (e.g. the gulf stream).  Also near the continents the sea depth becomes abruptly more shallow at decreases abruptly over the continental shelfsshelf.

The ocean-atmosphere coupling is carried out every hour and is achieved by a two-way interaction:

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NEMO and LIM2 forecast changes in the sea-surface temperature (SST) and sea ice evolution.  These are used interactively by all IFS atmospheric models.  Medium range ENS and extended range ENS use the same initial ice extent.  See also remarks on water surface temperature and sea ice. 

Note: ECMWF uses LIM2 which is an earlier version of the Louvain-la-Neuve sea ice model that is currently available (Version 3.6, LIM3)    

Fig23Fig2.A3-1: Sequence of sea-ice and sea-surface temperatures from the ENS CTRL run data time 00_UTC 27 April 2017.  T+0hr (00UTC 27 April 17), T+120hr (00UTC 02 May 17),  T+240hr (00UTC 07 May 17), and  T+360hr (00UTC 12 May 17).  On such plots the climatological average sea ice cover is shown in pink (contour and stippling, for >50%), just discernible in the northern Gulf of Bothnia and in the White Sea.   Dark purple areas (SST between 0C and -2C) are prone to ice formation if not already in existence.   Areas of sea ice are shown as turquoise. 

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