Abstract
As a consequence of ongoing climate warming, nearly all tidal glaciers in Arctic are retreating; hence, the seascape of glacial fjords is changing in many aspects. We took the example of Hornsund, the well-studied Svalbard fjord, with over 30 years of almost continuous observations of marine system. Recent data were collected during summer oceanographic surveys between 2001 and 2013 and compared with archival data from 1980s. As most of the phenomena connected with the warming happen at the sea surface (ice, wind, waves, surface currents, brackish water), we were interested, how the presumably stable, near-bottom waters in fjords behave, what are the environmental changes that are experienced directly by the worms living in the sediment. We have found that both the inner fjord basins (usually regarded as stable) and the outer fjord parts (exposed to the direct influence of shelf waters) has changed. Warming was documented in the inner basins, while cooling and warming episodes were recorded in the outer parts of the fjord. We demonstrate that following the increase melting and retreat of the glaciers, the area of shallows increased, salinity decreased and temperature increased—partly due to the advection of Atlantic waters from the shelf. Observed changes are in accordance with the model of arctic fjords evolution towards boreal ones associated with increased organic matter turnover. The observed changes are most likely typical for all cold water, glaciated fjords that are exposed to climate warming.
Highlights
Fjord oceanography was the focus of oceanographic research during the NATO Advance Science Workshop in 1980 and was later presented in baseline handbooks by Syvitski et al (1987)
Observed changes are in accordance with the model of arctic fjords evolution towards boreal ones associated with increased organic matter turnover
According to Pearson (1980), the functioning of fjords was controlled by hydrodynamic forcing, where hydrodynamic input was diminished from the ocean towards the inner fjord, resulting in carbon limitation in the outer fjord and nutrients sink in the inner fjord basin
Summary
Fjord oceanography was the focus of oceanographic research during the NATO Advance Science Workshop in 1980 and was later presented in baseline handbooks by Syvitski et al (1987). The basic paradigm of boreal and Arctic fjords was that they represented a particular case of estuarine circulation, with isolated basins and presence of residual near-bottom water in the innermost basin (Pearson 1980). Contrary to the shelf and open bays, there are not many complex oceanographical studies in Arctic fjords. Some well-studied fjords in Arctic that may serve as a comparison with the presented site are Kongsfjord, Van Mijen and Isfjord on Spitsbergen (Hop et al 2002; Svendsen et al 2002; Renaud et al 2007), Disco Bay and Young Sound on Greenland (Schmid and Piepenburg 1993; Rysgaard and Glud 2007), and Murres Inlet on Alaska (Powell and Molnia 1989). The marine system of Hornsund, the southernmost of the Spitsbergen fjords, has been investigated since the mid-1970s (Siwecki and Swerpel 1979; Urbanski et al 1980; Swerpel 1985; Gorlich et al 1987; Polar Biol (2016) 39:1411–1424
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