The hydrography of the Chupa Estuary, White Sea, Russia

This study was undertaken to determine the fate and fluxes of materials fro m Arctic estuaries to the coastal zone. The paper is the first of a series addressing questions relating to the physics and chemistry of the region. T hree seasonal cruises were undertaken in the Chupa Estuary, White Sea, Russ ia; in summer (July 1994), autumn (September, 1995) and spring (May/June 19 97). The Chupa is a fjord type estuary about 37 km long with several deep t roughs, connected by shallow sills, situated south of the Arctic circle on the western shore of kandalaksha Bay. Vertical profiles were carried out on an axial grid of 10 stations, at spring and neap tidal states, during whic h measurements were made of salinity, temperature, current spaed and direct ion, the concentration of suspended particulate material (SPM), pH, dissolv ed oxygen, nutrients (phosphate, silicate, nitrate, nitrite and ammonia) an d particulate trace metals in sediments and SPM (Millward et al., 1999, Est uarine, Coastal and Shelf Science, 48, 13-25). Additionally, sampling for t he hydrodynamic determinants was carried out On diurnal anchor stations at key points in the estuary. Vertical stratification was pronounced, particul arly in summer, with sharp gradients in temperature and salinity. A three l ayer vertical structure was observed with surface (0-5 m) and deep (20-65 m ) water layers providing net down-estuary transport while the intermediate (5-20 m) water layer drives net up-estuary transport and advection of more saline waters into the estuary. Strong internal waves were observed in the seaward half of the estuary at certain tidal states. The mechanism for rene wal of deep waters in the troughs was investigated, this bring considerably slower than in the near surface waters. Evidence of under-saturation of di ssolved oxygen was evident in the deep waters of the troughs during the thr ee surveys. (C) 1999 Academic Press.