Increasing freshwater discharge from the cryosphere into the ocean has the potential to affect both the chemical and physical mechanisms that regulate supply of macronutrients to primary producers on annual and geological timescales. Runoff around Greenland contributes to the stratification of the water column, reducing vertical fluxes of nutrients and the associated primary production in summer. Runoff is also often enriched in silicic acid (dSi) compared to nitrate (NO₃) and phosphate (PO₄) potentially leading to more favorable nutrient stoichiometry for diatoms.

The spatial and temporal scale over which solid and liquid discharge from the Greenland Ice Sheet affects marine biogeochemistry is however unclear. Low certainty remains concerning whether these impacts are confined to narrow fjord regions or extend to broad sections of the shelf. Here we combine new cruise data with a collation of the extensive work undertaken over the past century to constrain macronutrient distributions in Greenland’s coastal seas. Since 1920, over 38,000 publicly available measurement of macronutrient concentrations have been made on the Greenland shelf (arbitrary defined by the 600 m isobath). Freshening around Greenland is associated with a modest dSi enrichment, while direct changes to PO₄ and NO_x availability are small or negligible. A north to south dSi enrichment is evident along both east and west coastlines, likely driven by Arctic outflow rather than by local processes around Greenland. In all summertime sectors of the coastline, NO_x is drawn down to concentrations likely to limit primary production however some curious patches of elevated NO_x can be found throughout summer with varying apparent causes. Overall, the direct impact of processes related to the Greenland Ice Sheet on macronutrient distributions appears to be largely confined to fjords, though there are a few limited examples of nutrient anomalies propagating to the shelf in summer.

Greenlandic freshwater, macronutrients, coastal sea, past century