Sediment-laden meltwater plume variability in Kongsfjorden, Svalbard

The Arctic is warming at a rate of at least twice the global average. This is directly impacting upon the hydrological cycle; changing the balance of rain and snowfall, increasing losses of snow and glacier cover, and subsequently shifting the volumes and timing of meltwater runoff to nearby fjords and oceans. Sediment-laden meltwater plumes which are easily observable using satellite remote sensing, are good proxies for glacier runoff, both from subaerial rivers draining land-terminating glaciers, and subglacial discharge at tidewater glacier systems; they to bridge the gap between infrequent field observations and regular satellite data acquisitions. In-situ surface reflectance and surface water measurements were collected in July 2019, at the terrestrial glacier-fed Bayelva river plume, and the Blomstrandbreen subglacial discharge plume. These in-situ measurements, combined with Moderate Imaging Spectroadiometer (MODIS) satellite data were used to calibrate a relationship between surface reflectance and suspended sediment concentration at the two sediment-laden meltwater plumes. Using these empirical relationships, we determined seasonal sediment flux by establishing the thickness of the plume layer through conductivity, temperature and depth (CTD) profiles. Additionally, we determined plume metrics (area, extent or planform morphology and distribution), by integrating CTD profiles and measurements of meltwater runoff and sediment collected at the Bayelva hydrometric gauge, along with modelled datasets. We find that the sediment-laden meltwater plumes are extremely sensitive to variable inputs of meltwater runoff, with distinct changes in plume morphometry and sediment concentrations occurring at various points throughout the melt season, evidenced clearly during the transition from snow to firn and glacier ice melt, and after episodic rainfall events. Future work will apply these empirical relationships to other satellite datasets (including Planet, Sentinel and Landsat) from the last 20 years to determine long-term changes in the  sediment-laden meltwater plume systems, including their wider effects on fjord hydrography, and glaciomarine sedimentary processes in response to climatically-induced changes in the hydrology of the glacier systems.