Physical variability in Prince William Sound during the SEA Study (1994–98)

Abstract

From 1994 to 1998, a multidisciplinary ecosystem study (the Sound Ecosystem Assessment) examined the primary physical and biological factors that influence the production of pink salmon and Pacific herring in Prince William Sound (PWS), species that experienced population declines after the 1989 Exxon‐Valdez oil spill. Three physical processes are described that influence ecosystem processes: surface layer stratification; upper layer (<100 m) circulation; and exchange between PWS and the northern Gulf of Alaska (NGOA). Stratification formed first in the PWS nearshore regions in March, and subsequently in the northern central basin in April, primarily due to freshening. The northern stratified layer and the associated zonal density front persisted at least through June, but year‐to‐year differences occurred. In spring and summer, circulation in central PWS could be either cyclonic or anticyclonic. Drifter trajectories often linked central PWS to a nearshore bay or fjord, or one bay or fjord to another. September was characterized by a cyclonic circulation and isopycnal doming in central PWS, with little year‐to‐year variability. At Hinchinbrook Entrance, a main connection with the Gulf of Alaska, alternating inflows and outflows occurred in spring over all depths. In summer through early autumn (1995), in the absence of predominantly westward winds, the dominant exchange pattern was outflow above about 150 m and inflow below. In summer through early autumn (1996–98), there was also surface (<20 m) inflow at Montague Strait (the other main entrance). Northward transport at Hinchinbrook Entrance was maximum in late autumn through winter, with inflow above ~150 m and outflow below. Westward wind events over the shelf associated with the weather cycle drove inflow events at both Hinchinbrook Entrance and Montague Strait that may result in transport of zooplankton important to the PWS ecosystem.

Calcium carbonate corrosivity in an Alaskan inland sea

“…Bathymetry data are from a digital elevation model (DEM) provided by the National Oceanic and Atmospheric Administration (NOAA) National Geophysical Data Center (NGDC; http://www.ngdc.noaa.gov/mgg/coastal/). The red circle delineates the single station (PWS2) that was sampled during every survey of PWS from 2009 through 2012. surface layer (Niebauer et al, 1994;Musgrave et al, 2013;Halverson et al, 2012b;Vaughan et al, 2001). Downwellingfavorable winds, which dominate from September through May, drive surface flow into PWS through Hinchinbrook Entrance, with compensatory outflow through Montague Strait (Niebauer et al, 1994;Halverson et al, 2012a).…”

Transport through Prince William Sound: numerical study in a nowcast/forecast system

“…Initial estimate of monthly mean transport at HE based on EPWS/NFS simulation differs significantly from the climatological transport based on one-point ADCP moorings (Vaughan et al 2001). Further exploration of simulated transports at both HE and MS reveals more sophisticated patterns, thus requiring a separate study as presented in the sections below.…”

“…Based on these observations, general circulation pattern in PWS has been described as a portion of the westward flowing Alaska Coastal Current (ACC) on the GOA shelf that typically enters PWS through HE and transits the Sound from east to west before exiting through MS and rejoining the ACC, though there is much variation in the transport through HE (Niebauer et al 1994;Deleersnijder et al 1998). Recent investigations of circulation inside PWS challenge this simple throughflow picture in observations (Royer et al 1979;Vaughan et al 2001). For instance, at HE, alternating inflow and outflow occurred in spring over all depths; during summer through early autumn 1995, in the absence of predominately westward winds, the dominant exchange pattern between PWS and NGOA at HE was outflow above about 150 m and inflow below.…”

“…30 to 50 km diameter or mesoscale eddies) are suggested to be the sources of submesoscale eddies (Wang et al 2001). August and September have been characterized by a strong cyclonic circulation and isopycnal doming in the Central Sound, with little yearto-year variability (Cox 2004;Vaughan et al 2001).…”

An Ocean Observing and Prediction Experiment in Prince William Sound, Alaska

“…The remainder of this current continues across the mouth of Hinchinbrook Entrance, and then southwestward along Montague Island and westward again after rounding the southern tip of the island. Once in PWS, the upper-layer flow proceeds cyclonically around the central basin, with some of the flow feeding the waters exiting through Montague Strait (and also perhaps along the western side of Hinchinbrook Entrance) and some of it continuing into the northern PWS Vaughan et al 2001).…”