The Greenland Ice Sheet as a hot spot of phosphorus weathering and export in the Arctic

Abstract

The contribution of ice sheets to the global biogeochemical cycle of phosphorus is largely unknown, due to the lack of field data. Here we present the first comprehensive study of phosphorus export from two Greenland Ice Sheet glaciers. Our results indicate that the ice sheet is a hot spot of phosphorus export in the Arctic. Soluble reactive phosphorus (SRP) concentrations, up to 0.35 μM, are similar to those observed in Arctic rivers. Yields of SRP are among the highest in the literature, with denudation rates of 17-27 kg P km À2 yr À1. Particulate phases, as with nonglaciated catchments, dominate phosphorus export (>97% of total phosphorus flux). The labile particulate fraction differs between the two glaciers studied, with significantly higher yields found at the larger glacier (57.3 versus 8.3 kg P km À2 yr À1). Total phosphorus yields are an order of magnitude higher than riverine values reported in the literature. We estimate that the ice sheet contributes~15% of total bioavailable phosphorus input to the Arctic oceans (~11 Gg yr À1) and dominates total phosphorus input (408 Gg yr À1 ), which is more than 3 times that estimated from Arctic rivers (126 Gg yr À1 ). We predict that these fluxes will rise with increasing ice sheet freshwater discharge in the future.

Climate relevant trace gases (N2O and CH4) in the Eurasian Basin (Arctic Ocean)

“…4d). In effect, NO 3 -became limiting before the exhaustion of PO 4 3-, indicating the existence of previously mentioned P-excess in the system (YamamotoKawai et al, 2006;Hawkings et al, 2016). One of the most plausible origins of this PO 4 3-excess is the glaciers from Greenland.…”

“…The physical erosion of bedrock exposes ground apatite to biogeochemical weathering ultimately liberating PO 4 3-to the Arctic Ocean. Hawkings et al (2016) suggested that the Greenland Ice Sheets are the region of most efficient P weathering and export of PO 4 3-to surrounding regions, and that the export of dissolved phosphorous could equal that of the largest rivers in the world, like the Mississippi and the Amazon. In this study, the N/P ratio was strongly modified in the surface waters.…”

Ocean mixing and ice-sheet control of seawater 234 U/ 238 U during the last deglaciation

“…An interesting consequence of the basal melt inputs may be the associated release of nutrients to the ocean. Recent work from the Greenland Ice Sheet indicates dissolved phosphorus yields are at least equal to those associated with the Mississippi or Amazon rivers (32). In this regard, nutrients from direct subglacial weathering should be considered in the future as a potential source to fuel productivity in the North Atlantic during HS1.…”

Observed sediment and solute transport from the Kangerlussuaq sector of the Greenland Ice Sheet (2006–2016)

“…In recent years, there has been an increasing effort to quantify the magnitudes of chemical transport from the GrIS to adjacent seas, with special emphasis on nutrient export (e.g., Hawkings et al 2014Hawkings et al , 2015Hawkings et al , 2016Hawkings et al , 2017Wadham et al 2016). These estimates are almost all based on an upscaling from the Watson River catchment, or the subcatchment Leverett Glacier, to the entire GrIS.…”