A high-resolution, operational pan-Arctic meltwater discharge database from 1950 to 2021

The Arctic has warmed about four times faster than the global average during the last four decades. One of the consequences of this intensive warming is increasing Arctic land ice loss. In particular, mass loss from the Greenland Ice Sheet has been estimated to have increased sixfold between 1980 and 2020. Glaciers and ice caps outside of Greenland, though receiving less attention, have also been reported to be losing mass at an increasing rate. This is caused by a combination of negative surface mass balance – due to decreasing snowfall and/or increasing melting and runoff – and increasing ice discharge. However, negative surface mass balance due to increasing melting and runoff has become the dominant cause of mass loss in Greenland and the Canadian Arctic during the last 10-15 years. This indicates the increasing role of meltwater discharge into fjords and coastal seas, influencing a wide-range of physical, chemical and biological processes and also the large-scale oceanic circulation. Despite recent advancements, no meltwater discharge data products are available that cover the entire Arctic at a high spatial (< 1 km) and temporal (sub-monthly) resolution. To fill this data gap, we use daily ~6km runoff data from a regional climate model, Modéle Atmosphérique Régional (MAR), for the period of 1950-2021 – covering Greenland, Arctic Canada, Iceland, Svalbard, and Arctic Russia. We employ a statistical downscaling algorithm that utilises a high resolution (250 m) DEM, land mask (Copernicus GLO-90), and ice mask (GIMP, RGI). A hydrological routing scheme is also applied to the downscaled runoff to provide meltwater runoff data at coastal outflow points. Meltwater components coming from non glacierized land, bare glacier ice, and glacierized area above the snowline are separated to aid further analyses. The software pipeline is designed to be fully operational so that it can be used to update the time series as soon as the input data are available, so providing a continuous time series for the entire Arctic within the framework of a project aimed to develop a holistic, integrated observing system for the Arctic (www.arctipassion.eu).