Water mass modification in an Arctic fjord through cross‐shelf exchange: The seasonal hydrography of Kongsfjorden, Svalbard

Abstract

[1] Kongsfjorden and the West Spitsbergen Shelf is a region whose seasonal hydrography is dominated by the balance of Atlantic Water, Arctic waters, and glacial melt. Regional seasonality and the cross-shelf exchange processes have been investigated using conductivity-temperature-depth (CTD) observations from 2000-2003 and a 5-month mooring deployment through the spring and summer of 2002. Modeling of shelf-fjord dynamics was performed with the Bergen Ocean Model. Observations show a rapid and overwhelming intrusion of Atlantic Water across the shelf and into the fjord during midsummer giving rise to intense seasonality. Pockets of Atlantic Water, from the West Spitsbergen Current, form through barotropic instabilities at the shelf front. These leak onto the shelf and propagate as topographically steered features toward the fjord. Model results indicate that such cross-front exchange is enhanced by north winds. Normally, Atlantic Water penetration into the fjord is inhibited by a density front at the fjord mouth. This geostrophic control mechanism is found to be more important than the hydraulic control common to many fjords.

Impact of aragonite saturation state changes on migratory pteropods

“…This difference is explained by the different physicalchemical properties of the two areas. Svalbard waters are influenced by Atlantic water [37], with higher total alkalinity and temperature. The influence of Atlantic inflow in this area makes these waters less susceptible to undersaturation than those at higher latitudes (e.g.…”

Effects of undercutting and sliding on calving: a global approach applied to Kronebreen, Svalbard

“…Sediment-rich fresh meltwater discharge is thus mixing with saline fjord waters and can lead to a significant melt rate at the front of the glacier. Large variations of marine processes are typical for arctic fjords and Kongsfjorden experiences significant influx of warm water masses during the summer (Cottier et al, 2005) as shown by observations presented by Nahrgang et al (2014) of ocean temperatures of Kongsfjorden from moored observatories in 2012-2013. From October to mid-November 2012, the whole water column temperature was warm (4-5 • C).…”

“…However, with a non-uniform ambient temperature and salinity, the effects of changes in the stratification on the plume vertical velocity and neutral buoyancy are much more complex. The stratification in Kongsfjorden is a multi-layer system, with little or no direct relationship between changes in different layers (Cottier et al, 2005). Therefore, testing cases by uniformly increasing or decreasing the salinity would not be informative for understanding the true effects of inter-and intra-annual variability.…”

Spring bloom dynamics in Kongsfjorden, Svalbard: nutrients, phytoplankton, protozoans and primary production

“…Relatively warm Atlantic water (AW, [3°C) is carried along the west coast of Spitsbergen by the west Spitsbergen current (WSC) and is advected into Kongsfjorden at irregular intervals where it mixes with the colder local water (LW, -0.5 to 1.0°C) (Svendsen et al 2002;Cottier et al 2005). The advection of Atlantic water across the shelf during summer, changes the water mass inside the fjord from Arctic dominance in winter to Atlantic dominance in summer (Svendsen et al 2002).…”

“…These advective processes affect all parts of the marine ecosystem inside the fjord (Hop et al 2002). Major inter-annual variations in ocean temperature have been registered by Cottier et al (2005). They demonstrated that the fjord water showed distinct inter-annual variability in the heat content and in the timing and duration of the advective period, giving rise to the concept of warm and cold years.…”