Silicon Cycling in Greenlandic fjords: Comparison of Marine and Land-Terminating Glaciers

Meltwaters from glaciers and ice sheets in the Arctic region potentially provide significant fluxes of key nutrients to downstream ecosystems, and hence recent acceleration of melting has implications for the high-latitude biogeochemical cycles. Previous work has shown that silicon (Si) exported from glacial environments also has a distinct isotopic signature compared to those in non-glacial rivers. However, the extent to which glacially-derived Si and other bioavailable nutrients reach the open ocean is much debated, due to biological uptake and complex physical processes within heterogeneous fjord environments.

We assess the impact of glacial meltwater from marine and land-terminating glaciers on fjord biogeochemistry, with a focus upon Si cycling, by sampling two fjords (Godthåbsfjord and Ameralik Fjord) in southwest Greenland over two melt seasons. We combine silicon isotope measurements with a range of complementary physical and chemical parameters to evaluate the role of glacially derived nutrients and benthic recycling on biological productivity within the two contrasting fjord environments. Data from two consecutive melt seasons also enables us to begin to assess inter-annual variability. In addition, continuous measurements of silicic acid and nitrate concentrations along Godthåbsfjord during the 2019 melt season, obtained using novel sensor technology, allow us to assess intra-annual variations in nutrient export. Our targeted field campaigns have provided a suite of nutrient, trace element and isotopic data that will improve the current understanding of the complex biogeochemical cycling within fjord environments, and allow a better assessment of the importance of glacial meltwater on nutrient export and primary productivity in downstream ecosystems.