Chemical Distribution Patterns across the west Greenland Shelf: The Roles of Ocean Currents, Sea Ice Melt, and Freshwater Runoff

The west Greenland shelf is a dynamic marine environment influenced by various physicochemical and biological processes. We captured a high-resolution, large-scale snapshot of various water column parameters across the west Greenland shelf and Davis Strait between 64°N and 71°N during July 2021. This study provides an overview of the main factors affecting the distribution of macronutrients (NOx = nitrate + nitrite, silicate, phosphate), carbonate system parameters (alkalinity (AT), dissolved inorganic carbon (CT)), and dissolved trace elements (dV, dFe, dMn, dCo, dNi, dCu, dCd, and dPb) during late summer. The key drivers include major ocean currents, melting sea ice, and terrestrial freshwater runoff, each uniquely contributing to the cycling and spatial distribution of chemical constituents.

Major ocean currents, such as the southward-moving Baffin Island Current (BIC) and the northward-moving West Greenland Current (WGC), shape the chemical composition of shelf waters by introducing water masses with distinct chemical signatures. The northward-moving West Greenland Shelf Water (WGSW) was characterized as warm (2.68°C), fresh (33.57), and highly productive, with overall low nutrient concentrations. In contrast, the southward-moving Arctic water (AW) was cold (0.38°C) and fresh (33.48), with high nutrient contents due to lower biological activity. The inflow of Pacific-origin waters through the Canadian Archipelago (CAA) to Baffin Bay was responsible for elevated dFe, dMn, dCo, dNi, and dCu concentrations.

The progressive melting and retreat of sea ice altered both the biological productivity and the chemical composition of surface waters in southern Baffin Bay. The east-to-west direction of sea ice retreat created a nutrient gradient, with low nutrient levels in the highly productive shelf waters to the east and high nutrient levels in areas with prolonged ice cover to the west. This process also affected the carbonate system, leading to changes in pH and aragonite saturation states, which are critical for the health of marine organisms. Furthermore, we observed sea ice meltwater as a source of dFe, dCo, dNi, dCu, and dCd to Baffin Bay surface waters. This additional source of bioactive trace elements could maintain and prolong ice-edge blooms.

Terrestrial freshwater runoff from the Greenland Ice Sheet (GIS), particularly in Disko Bay and at the mouth of the Nassuttooq Fjord, replenished macronutrients in the photic zone, stimulating primary production (PP) and creating significant CO₂ sinks. However, in areas along the coastline where PP was limited by low nutrient concentrations, surface waters became more susceptible to acidification via input of poorly buffered glacial freshwater.

This work provides a summarized overview of the complex interplay between the chemical composition of the west Greenland shelf and major ocean currents, melting sea ice, and terrestrial freshwater runoff from the GIS. Understanding these key drivers is essential for forecasting future changes of the marine chemistry and biology of the west Greenland shelf, especially in the context of ongoing climate change within this high-latitude region.