Continued glacial retreat linked to changing macronutrient supply along the West Antarctic Peninsula

At the West Antarctic Peninsula (WAP), continued atmospheric and oceanic warming is causing significant physical and biogeochemical changes to glaciers and the marine environment. We compare sediment sources and drivers of macronutrient distributions at two bays along the WAP during austral summer 2020, using radioactive radium and stable oxygen isotopes to trace sedimentary influences and quantify different freshwater inputs. In the Ryder Bay, where the Sheldon Glacier is marine-terminating, radium activities at the sediment-water interface indicate considerable benthic mixing. Using radium isotope activity gradients to resolve radium and macronutrient fluxes, we find buoyant meltwater proximal to the glacier drives vigorous mixing of sediment and entrainment of macronutrient deep waters, on the order of 2.0 x 105 mol d-1 for nitrate. Conversely, in the Marian Cove, where the Fourcade Glacier terminates on land, low salinities and oxygen isotopes indicate a meltwater-rich surface layer <1 m thick and rich in sediment, and strong vertical mixing to the seafloor. A continued shift to land-terminating glaciers along the WAP may have a significant impact upon nutrient and sediment supply to the euphotic zone, with impacts upon primary productivity and carbon uptake efficiency. The future of primary production, carbon uptake, and food web dynamics is therefore linked to glacier retreat dy-namics in the many fjords along the WAP.

Automated summary

Continued atmospheric and oceanic warming at the West Antarctic Peninsula (WAP) is causing significant changes to glaciers and the marine environment. Two bays along the WAP were compared during austral summer 2020 to study sediment sources and drivers of macronutrient distributions. The study found that land-terminating glaciers have a meltwater-rich surface layer with strong vertical mixing, while marine-terminating glaciers drive vigorous mixing of sediment and entrainment of macronutrient deep waters. This shift to land-terminating glaciers may have a significant impact on nutrient and sediment supply to the euphotic zone, affecting primary productivity and carbon uptake efficiency.