A One-Dimensional Time-Dependent Model for the Vertical Stratification of the Upper Arctic Ocean

Abstract

A one-dimensional time-dependent model of the upper Arctic Ocean is presented. It describes the circulation above a dynamically passive reservoir of Atlantic water. The model is driven by freshwater runoff from land, ice production and export, Bering Strait inflow and wind. The mixed layer thickness is controlled by the shortest among the following three length scales; the depth to the upper pycnocline, the Ekman length and the Monin-Obukov length. The outflow is assumed to occur as geostrophically controlled coastal currents. Four integral quantities are defined in order to make objective comparisons between model generated and observed salt and temperature profiles. The model generates a seasonally varying mixed layer in qualitative agreement with measurements. A halocline with water near the freezing temperature is also generated. This structure is sustained by the water coming from the Bering Strait. By comparing the model result with the observed freshwater content in the basin, likely values of the Bering Strait inflow Qb and the ice export Ql are found. These values are presented as an area in theQl, Qb plane. It is shown that with this model, lacking shelf processes, it is impossible to obtain correct values for all integral quantities. The deviation between the computed and the observed stratification suggests that the Arctic Ocean has an internal source of salty water at temperature near the freezing point. This internal source of dense water is probably driven by ice production and the accompanying ejection of salt on the large shelf areas. By introducing a hypothetical shelf with a prescribed distribution of outflow as a function of salinity it is possible to obtain nearly full agreement with the observed stratification. It is shown that the best fit is achieved when the volume flow from the shelf is in the interval (1?1.5) ? 106 m3 s?1.