Geophysical Institute

A review is given of volume and heat budgets for the Arctic Ocean and the Nordic Seas based on oceanic transport observations. The present preferred estimates indicate a northward transport of about 300 TW through the Greenland-Scotland passage of which 50-80 TW continues into the Arctic Ocean. The net budgets for the Nordic Seas are about 220-250 TW. Regional surface heat budgets are computed based on climatological data from the Comprehensive Ocean Atmosphere Data Set and European Centre for Medium Range Weather Forecasts in addition to monthly mean weather station temperature data from the Carbon Dioxide Information Center database. Each of the terms in the sea surface heat budget is computed with several parameterizations, which are frequently applied in heat budget calculations and in ocean and sea ice modeling. Combining all parameterizations for each term provides 90 different parameterizations of the sea surface heat budget. On the basis of identical climatological data, the surface heat budgets for the Nordic Seas vary from a heat loss of 304 TW to a heat gain of 52 TW. The heat loss from the Barents Sea is in the range from 42 to 162 TW. Twelve combinations of the parameterizations provide a heat budget for the Nordic Seas which is within the advective estimates. One is selected for use in ocean modeling of this region. The same parameterizations provide a heat loss of 129-147 TW (or 98-112 Wm -•) from the Barents Sea. Published volume transports and temperatures indicate that the heat loss from the Barents Sea is only within 28-80 TW. Our results suggest that the heat transport from the Norwegian Sea to the Barents Sea is larger than recent advective estimates and thus that the Barents Sea plays a major role in renewal of the deep water and the thermohaline circulation of the Arctic Mediterranean.

A simple two-layer, quasi-geostrophic model with bottom topography is shown to reproduce several features of the mesoscale circulation on the Norwegian continental shelf between 62øN and 66øN, as observed with in situ and remote sensing instruments during the Norwegian Continental Shelf Experiment (NORCSEX '88). The widening of the shelf, its steplike deepening northeastward along the coast, and the presence of the Haltenbank generate intense eddy activity. Further northeast, Atlantic Water is steered anticyclonically around the Haltenbank, and the Norwegian Coastal Current is squeezed toward the coast. The variability of the modeled and observed near-surface current is shown by ray-tracing calculations to be able to generate significant wave-current refraction. In addition to its importance for wave modeling and prediction, this fact opens possibilities for indirect surface current measurements from directional wave observations, particularly from synthetic aperture radar. 1. Paper number 91JC00299. 0148-0227/91/91J C-00299505.00 independent. Their resulting capability to regularly detect mesoscale circulation patterns makes them attractive [Guddal et al., 1989]. The Norwegian Continental Shelf Experiment (NORC-SEX '88) conducted off the west coast of Norway centered at 64øN in March 1988, was dedicated as a prelaunch ERS 1 investigation aimed at measuring near-surface wind, waves and currents from active microwave sensors [NORCSEX '88 Group, 1989; Johannessen et al., this issue]. Although the in situ oceanographic data collection (Table 1) was not primarily directed at detecting and tracking mesoscale eddy features, it provides satisfactory data for testing and validation of the QG model. A summary of the general circulation pattern in the experimental region is given in section 2. The numerical model is presented in section 3, and model results are compared with observations from NORCSEX '88 in section 4. The relevance of SAR and altimeter data in combination with the model data for detection of mesoscale circulation pattern is discussed in sections 5 and 6. Conclusions are then given in section 7. 2. GENERAL CIRCULATION PATTERN The depth and time-averaged currents at each mooring during the NORCSEX '88 period (Figure lb and Table 1) vary from 0.07 m s -• to 0.20 m s -• with a mean northeastward direction, except for CM3 located north-northeast of the Haltenbank which shows a south-southeasterly flow direction. These directions are nearly parallel to the isobaths, documenting significant influence of topographic steering. Minor vertical shear and turning angle of the current are found on all moorings except at CM2 located in the channel east of Haltenbank, where the speed decreases from 0.30 m s -• at 25 m to 0.10 m s -• at 150 m, while the direction remains unchanged. During winter the NCC is characterized by cold and fresh coastal water with temperature ranging from 2 ø to 5øC and salinity less than 34.8%0, while the AW has a temperature exceeding 6øC and salinity greater than 35%0 [Scetre and LjOen, 1972]. A well-defined frontal boundary forms be-10,487 10,488 HAUGAN ET AL.' MODELED AND OBSERVED MESOSCALE CIRCULATION IN NORCSEX '88