Pan-Arctic distributions of continental runoff in the Arctic Ocean

Abstract

Continental runoff is a major source of freshwater, nutrients and terrigenous material to the Arctic Ocean. As such, it influences water column stratification, light attenuation, surface heating, gas exchange, biological productivity and carbon sequestration. Increasing river discharge and thawing permafrost suggest that the impacts of continental runoff on these processes are changing. Here, a new optical proxy was developed and implemented with remote sensing to determine the first pan-Arctic distribution of terrigenous dissolved organic matter (tDOM) and continental runoff in the surface Arctic Ocean. Retrospective analyses revealed connections between the routing of North American runoff and the recent freshening of the Canada Basin, and indicated a correspondence between climate-driven changes in river discharge and tDOM inventories in the Kara Sea. By facilitating the real-time, synoptic monitoring of tDOM and freshwater runoff in surface polar waters, this novel approach will help understand the manifestations of climate change in this remote region.

Carbon geochemistry of plankton-dominated samples in the Laptev and East Siberian shelves: contrasts in suspended particle composition

“…The Lena (523 km 3 yr −1 ), Indigirka (54 km 3 yr −1 ), and Kolyma (48 km 3 yr −1 ) are the major rivers (Gordeev, 2006). During the ice-free season, the Lena plume can be traced in the outer shelf of the Laptev Sea (Fichot et al, 2013;Salvadó et al, 2016;Sánchez-García et al, 2011) while Pacific inflow from the Bering strait affects further east the East Siberia margin (Semiletov et al, 2005). The Pacific inflow exerts control on the nutrient balance as it supplies phosphorous and silicate to an otherwise nutrient-depleted region (Anderson et al, 2011;Semiletov et al, 2005).…”

“…The land-derived material that does not settle in the coastal zone further travels across the continental margin reaching out to the outer-shelf region resuspended within the ben- thic nepheloid layer or in suspension within the surface river plume (Fichot et al, 2013;Sánchez-García et al, 2011;Wegner et al, 2003). Another fraction of terrestrial material can travel across the Siberian margin trapped in fast ice (Dethleff, 2005).…”

Optical properties and bioavailability of dissolved organic matter along a flow-path continuum from soil pore waters to the Kolyma River mainstem, East Siberia

“…Previous studies have indicated that CDOM spectral slopes (particularly S 290−350 and S 275−295 ) can serve as indicators of DOM source and composition, where a steeper spectral slope typically suggests lower molecular weight material with decreasing aromatic content and a shallower (i.e., lower) slope typically suggests higher molecular weight material with increasing aromatic content (Green and Blough, 1994;Blough and Del Vecchio, 2002;Helms et al, 2008;Spencer et al, 2009a). Furthermore, S 275−295 has been identified as a reliable proxy for dissolved lignin and therefore terrigenous DOM supply across Arctic Ocean coastal waters, as well as photobleaching history (Helms et al, 2008;Fichot et al, 2013). We found a general increase in S 290−350 and S 275−295 moving downstream through the network, indicative of progressive photodegradation of DOM alongside likely reductions in average DOM molecular weight and aromaticity.…”

Characteristics of chromophoric and fluorescent dissolved organic matter in the Nordic Seas

“…The riverine input can be monitored by optical methods with absorption, fluorescence, or remote-sensing measurements (Spencer et al, 2012;Walker et al, 2013;Fichot et al, 2013;Mann et al, 2016). The largest DOC concentrations were found in the Siberian rivers Lena -1300 µmol L −1 , Yenisey -842 µmol L −1 , and Ob -950 µmol L −1 , and the concentrations were lower in the North American Yukon -816 µmol L −1 and McKenzie -648 µmol L −1 rivers Mann et al, 2016).…”