The biogeochemical impact of glacial meltwater from Southwest Greenland

Abstract

Biogeochemical cycling in high-latitude regions has a disproportionate impact on global nutrient budgets. Here, we introduce a holistic, multidisciplinary framework for elucidating the influence of glacial meltwaters, shelf currents, and biological production on biogeochemical cycling in high-latitude continental margins, with a focus on the silica cycle. Our findings highlight the impact of significant glacial discharge on nutrient supply to shelf and slope waters, as well as surface and benthic production in these regions, over a range of timescales from days to thousands of years. Whilst biological uptake in fjords and strong diatom activity in coastal waters maintains low dissolved silicon concentrations in surface waters, we find important but spatially heterogeneous additions of particulates into the system, which are transported rapidly away from the shore. We expect the glacially-derived particles-together with biogenic silica tests-to be cycled rapidly through shallow sediments, resulting in a strong benthic flux of dissolved silicon. Entrainment of this benthic silicon into boundary currents may supply an important source of this key nutrient into the Labrador Sea, and is also likely to recirculate back into the deep fjords inshore. This study illustrates how geochemical and oceanographic analyses can be used together to probe further into modern nutrient cycling in this region, as well as the palaeoclimatological 3 approaches to investigating changes in glacial meltwater discharge through time, especially during periods of rapid climatic change in the Late Quaternary.

Weathering Dynamics Under Contrasting Greenland Ice Sheet Catchments

“…This is likely explained by the elevated physical erosion rates from Leverett Glacier and other large glaciers draining into the Watson River, which are at least an order of magnitude larger in size than Kiattuut Sermiat (Hawkings et al, 2017). This supports the hypothesis made in recent studies that GrIS exports large fluxes of reactive silica to neighboring ecosystems, where it may be important in stimulating the productivity of siliceous organisms (Meire et al, 2016;Hawkings et al, 2017;Hendry et al, 2019).…”

Terrestrial Inputs Drive Seasonality in Organic Matter and Nutrient Biogeochemistry in a High Arctic Fjord System (Isfjorden, Svalbard)

“…These concentrations are higher than concentrations measured from AW advected from the shelf (maximum of 2 µmol L −1 for NO 2 + NO 3 and 0.4 µmol L −1 for PO 4 in this study, but other observations from Svalbard show 6-11 µmol L −1 for N and 0.8 µmol L −1 for P (Chierici et al, 2019;Halbach et al, 2019). While SiO 2 has been associated with glacial meltwater from contact with silica-rich bedrock in Isfjorden (Fransson et al, 2015), Kongsfjorden (Halbach et al, 2019) and Greenland fjords (Meire et al, 2016;Kanna et al, 2018;Hendry et al, 2019), N and P have been linked primarily to advected deep water. In contrast to glacial meltwaters in Kongsfjorden (Halbach et al, 2019) and Greenland (Paulsen et al, 2017), the rivers sampled in our study had comparably high concentrations of N and P in addition to SiO 2 .…”

Sponge Density and Distribution Constrained by Fluid Forcing in the Deep Sea

“…The ability to scale up the distributions described here are limited due to the small study area. Their size is limited by the diameter of the areas surveyed by the ROV (Hendry, 2017;Hendry et al, 2019). However, our flow-modeling method could be extended to a broader geographical area, and combined with localized environmental data and predictions, to make inferences about environmental driving factors for sponge distribution in sponge grounds on wider spatial and temporal scales.…”