Alistair Everett is a Research Scientist at the Norwegian Polar Institute interested in ice-ocean interactions at marine-terminating glaciers. Here he describes recent research as part of the TIGRIF project, which seeks to understand the influence of tidewater glaciers on fjord dynamics and marine ecosystems, with particular focus on how these fjords may change in future when the glaciers retreat onto land.

In a recently published study (Everett et al. 2018), we investigated the water properties close to a glacier terminus in Kongsfjorden, northwestern Svalbard using a unique dataset collected by ringed seals (Pusa hispida) instrumented with GPS-CTD-SRDLs in 2012. The dataset had already been used to look at seal behaviour and their response to variations in sea ice (Hamilton et al., 2016). But in this new study the focus was instead on glaciology and the meltwater plume that could be observed very close to the glacier terminus; a place where it remains otherwise very challenging to collect data with boats and conventional CTD instruments.

The SRDLs used in this study (glued onto the hair of the seals) collected over one thousand CTD profiles within our study area during a period of around four months, providing us with a valuable time-series of oceanographic data. We were particularly interested in a number of profiles that showed ‘spikes’ of low temperature and salinity at depths of up to 60 metres. In our study, we showed that these ‘spikes’ were caused by the seals entering plumes of meltwater released from underneath the glacier. This was supported by running a clustering algorithm on the GPS locations returned by the SRDLs, which showed that the seals focused their foraging in plume locations, particularly during periods of high meltwater runoff from the glacier.

The data collected by the seals in Kongsfjorden provide important insights into a region where it has previously been very difficult to collect data. The results highlight the importance of plumes and marine-terminating glaciers for the ecosystems in these fjords. Further measurements within plumes can help us to constrain the volume of subglacial discharge, the associated melt rates and the influence on fjord circulation. In the future, as these glaciers retreat onto land, the plumes will eventually disappear, leading to the loss of this important foraging area for ringed seals and changes to the upwelling and circulation patterns within these fjords.

References:

Everett, A., Kohler, J., Sundfjord, A., Kovacs, K.M., Torsvik, T., Pramanik, A., Boehme, L., Lydersen, C., 2018. Subglacial discharge plume behaviour revealed by CTD-instrumented ringed seals. Sci. Rep. 8 (1), https://doi.org/10.1038/s41598-018-31875-8.

Hamilton, C. D., Lydersen, C., Ims, R. A. & Kovacs, K. M. 2016. Coastal habitat use by ringed seals Pusa hispidafollowing a regional sea-ice collapse: importance of glacial refugia in a changing Arctic. Mar. Ecol. Prog. Ser. 545, 261–277, https://doi.org/10.3354/meps11598.