Ryabchenko V. A., Gorchakov V. A., Dvornikov A. Yu., Pugalova S. S.
This study is aimed to assess the impact of sea ice on the primary production of phytoplankton in the Barents Sea. To get the estimations, we apply a three-dimensional eco-hydrodynamic model based on the Princeton Ocean Model which includes a module of sea ice with 7 categories and the 11-component module of marine pelagic ecosystem developed in Saint-Petersburg Department of the P.P. Shirshov Institute of Oceanology of RAS. The comparison of the model results for the period 1998—2007 with satellite data showed that the model reproduces the main features of the evolution of the sea surface temperature, seasonal changes in the ice extent, surface chlorophyll-a concentration and the primary production of phytoplankton in the Barents Sea. Model estimates of the annual primary production of phytoplankton for the whole sea turned out to be 1.5—2.3 times higher than similar estimates from satellite data. The main reason for this discrepancy is that the model takes into account the production of the primary production of phytoplankton under the pack ice and the marginal ice zone, and satellite data refer exclusively to the open water. Moreover, the evaluation of the primary production of phytoplankton from satellite data underestimates its importance due to subsurface maximum of chlorophyll. During the period 1998—2007, the modelled maximal (in the seasonal cycle) sea ice area has decreased by 15 %. This reduction was accompanied by an increase in the annual primary production of phytoplankton of the sea at 54 and 63 %, based, respectively, on satellite data and the model for the open water. According to the model calculations for the whole sea area, the increase is only 19 %. We conclude that an adequate assessment of the primary production in ice-covered seas can only be obtained on the basis of eco-hydrodynamic models, including sea ice.