Inorganic carbon and nutrient fluxes on the Arctic Shelf

Abstract

Historic data from the Russian-American Hydrochemical Atlas of Arctic Ocean together with data from the TRANSDRIFT II 1994 and TUNDRA 1994 cruises have been used to assess the spatial and inter-annual variability of carbon and nutrient fluxes, as well as air–sea CO 2 exchange in the Laptev and western East Siberian Seas during the summer season. Budget computations using summer data of dissolved inorganic phosphate (DIP), dissolved inorganic nitrogen (DIN) and dissolved inorganic carbon (DIC) gives that the Laptev Sea shelf is a net sink of DIP and DIN of 2.5×10 6, 23.2×10 6 mol d −1, respectively, while it is a net source of DIC (excluding air–sea exchange) of 1249×10 6 mol d −1. In the East Siberian Seas the budget computations give 0.5×10 6, −11.4×10 6 and −173×10 6 mol d −1 (minus being a sink) for DIP, DIN, and DIC, respectively. In summers, the Laptev Sea Shelf is net autotrophic while the East-Siberian Sea Shelf is net heterotrophic, and both systems are weak net denitrifying. The Laptev Sea Shelf takes up 2.1 mmol CO 2 m −2 d −1 from atmosphere, whereas the western part of the East-Siberian Sea Shelf loose 0.3 mmol CO 2 m −2 d −1 to the atmosphere. The variability of DIP, DIN and DIC fluxes during summer in the different regions of the Laptev and East Siberian Seas depends on bottom topography, river runoff, exchange with surrounding seas and wind field.