Abstract
AbstractThe 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−2 yr−1. 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−2 yr−1). 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−1) and dominates total phosphorus input (408 Gg yr−1), which is more than 3 times that estimated from Arctic rivers (126 Gg yr−1). We predict that these fluxes will rise with increasing ice sheet freshwater discharge in the future.
Highlights
Phosphorus (P) is a bioessential macronutrient [Ruttenberg, 2014]
We estimate that the ice sheet contributes ~15% of total bioavailable phosphorus input to the Arctic oceans (~11 Gg yrÀ1) and dominates total phosphorus input (408 Gg yrÀ1), which is more than 3 times that estimated from Arctic rivers (126 Gg yrÀ1)
We find dissolved phosphorus yields are at least equal to some of the world’s largest rivers, such as the Mississippi and the Amazon
Summary
Phosphorus (P) is a bioessential macronutrient [Ruttenberg, 2014]. The supply of P is known to influence ecosystem productivity and biogeochemical cycles in marine and terrestrial ecosystems. Many aspects of the current global P cycle are poorly understood [Filippelli, 2008], especially terrestrial fluxes of P to the oceans, the principal speciation of P exported and the associated bioavailability of fluxes [Slomp, 2011]. Studies of the transport of P to the ocean have so far focused on riverine runoff, atmospheric deposition, and submarine groundwater discharge. Two studies have suggested a role for glaciers in the global P cycle [Föllmi et al, 2009; Hodson et al, 2004]. These have focused on small glacial systems, which may have lower chemical weathering intensities than larger ice sheet catchments [Wadham et al, 2010]. Ice sheets have largely been overlooked as P sources to the oceans
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