Kenneth F. Drinkwater

Pathways between Primary Production and Fisheries Yields of Large Marine Ecosystems

The shift in marine resource management from a compartmentalized approach of dealing with resources on a species basis to an approach based on management of spatially defined ecosystems requires an accurate accounting of energy flow. The flow of energy from primary production through the food web will ultimately limit upper trophic-level fishery yields. In this work, we examine the relationship between yield and several metrics including net primary production, chlorophyll concentration, particle-export ratio, and the ratio of secondary to primary production. We also evaluate the relationship between yield and two additional rate measures that describe the export of energy from the pelagic food web, particle export flux and mesozooplankton productivity. We found primary production is a poor predictor of global fishery yields for a sample of 52 large marine ecosystems. However, chlorophyll concentration, particle-export ratio, and the ratio of secondary to primary production were positively associated with yields. The latter two measures provide greater mechanistic insight into factors controlling fishery production than chlorophyll concentration alone. Particle export flux and mesozooplankton productivity were also significantly related to yield on a global basis. Collectively, our analyses suggest that factors related to the export of energy from pelagic food webs are critical to defining patterns of fishery yields. Such trophic patterns are associated with temperature and latitude and hence greater yields are associated with colder, high latitude ecosystems.

Wind‐ and buoyancy‐induced transport of the Norwegian Coastal Current in the Barents Sea

[1]xa0The focus of this study is on the fluxes and forcing of the Norwegian Coastal Current (NCC) at the entrance to the Barents Sea. The structure and dynamics of the NCC, which consists of a slope branch and an offshore branch, are investigated using (1) a recent 1 year full depth current meter record in the core of the slope region; (2) repeated hydrographic data at an inshore monitoring station; (3) broader regional hydrographic surveys; and (4) atmospheric reanalysis data. The total fluxes are estimated to 1.8 Sv for volume and 26 mSv for freshwater relative to a reference salinity of 34.8, with the largest contributions from baroclinic offshore branch. The heat flux calculated for the slope branch only is 34 TW. These estimates are higher compared to earlier estimates but are based on more comprehensive data. The major mode of variability in the slope branch is consistent with a continental shelf wave on time scales in the range of 3–16 days forced by the along-coast component of the wind stress. Maximum along-slope currents during fall/winter, corresponding to the stronger wind forcing during these seasons, suggest that the observed seasonality in the NCC can be attributed to a similar mechanism.