Variability in transport of terrigenous material on the shelves and the deep Arctic Ocean during the Holocene

Abstract

Arctic coastal zones serve as a sensitive filter for terrigenous matter input onto the shelves via river discharge and coastal erosion. This material is further distributed across the Arctic by ocean currents and sea ice. The coastal regions are particularly vulnerable to changes related to recent climate change. We compiled a pan-Arctic review that looks into the changing Holocene sources, transport processes and sinks of terrigenous sediment in the Arctic Ocean. Existing palaeoceanographic studies demonstrate how climate warming and the disappearance of ice sheets during the early Holocene initiated eustatic sea-level rise that greatly modified the physiography of the Arctic Ocean. Sedimentation rates over the shelves and slopes were much greater during periods of rapid sea-level rise in the early and middle Holocene, as a result of the relative distance to the terrestrial sediment sources. However, estimates of suspended sediment delivery through major Arctic rivers do not indicate enhanced delivery during this time, which suggests enhanced rates of coastal erosion. The increased supply of terrigenous material to the outer shelves and deep Arctic Ocean in the early and middle Holocene might serve as analogous to forecast changes in the future Arctic.To access the supplementary material for this article, please see supplementary files under Article Tools online.Rapid changes in the environmental conditions of the Arctic have been observed over recent decades. These include decreasing summer and winter sea-ice extent, increasing annual river discharge, increasing areal extent of open-water areas over the Arctic shelves and lengthening of the open-water season Serreze et al. 2007;Kwok et al. 2009;Wagner et al. 2011;Stroeve et al. 2012;Fichot et al. 2013;Zhang et al. 2013). These changes will likely lead to important transformations in sedimentary environments and the pathways and processes of terrigeneous particulate cycling. In particular, they could play a role in sediment resuspension and coastal erosion (e.g., Atkinson 2005;Eicken et al. 2005; Carmack et al. 2006; Anisimov et al. 2007;Lantuit et al. 2012).The impact of increased export of turbid waters from rivers and coastal regions on Arctic marine ecosystems remains uncertain; it could either increase delivery of nutrients and promote productivity or suppress photosynthesis in the light-limited algal populations by scattering absorbing sunlight (Retamal et al. 2008). An adequate understanding of the pathways of terrigenous material is needed to elucidate connections between sediment and ecosystem dynamics under a changing climate. Research efforts assessing recent trends and variability of terrigenous particulate matter inputs into the Arctic Ocean have been carried out during the past decades and discussed in reviews by Rachold et al. (2004), Macdonald et al. (2010), Forbes (2011) and Goñ i et al. (2013). However, the ability to forecast the future significance of land-derived sedimentary inputs into the Arctic Ocean also needs to account for th...

Dissolved organic carbon (DOC) in Arctic ground ice

“…Several studies have shed light on the POC stocks contained in permafrost (e.g., Zimov et al, 2006a;Tarnocai et al, 2009;Schirrmeister et al, 2011b;Strauss et al, 2013;Hugelius et al, 2013Hugelius et al, , 2014Walter Anthony et al, 2014) and how much of these stocks is potentially mobilized due to thermal permafrost degradation and coastal erosion Jorgenson and Brown, 2005;Lantuit et al, 2009;McGuire et al, 2009;Ping et al, 2011;Schneider von Deimling et al, 2012;Vonk et al, 2012;Günther et al, 2013Günther et al, , 2015Wegner et al, 2015). DOC fluxes have also been quantified in western Siberian catchments (Frey and Smith, 2005), and monitoring efforts of the large rivers draining permafrost areas and entering into the Arctic Ocean have provided robust estimations of the riverine DOC export (Raymond et al, 2007;McGuire et al, 2009).…”

Summer rainfall dissolved organic carbon, solute, and sediment fluxes in a small Arctic coastal catchment on Herschel Island (Yukon Territory, Canada)

“…As rainfall frequency and intensity are projected to increase in the future (Bintanja and Andry 2017), more organic matter, nutrients, and sediment could be mobilized and transported from coastal areas into nearshore zones of the Arctic Ocean. The eight largest Arctic Rivers cover 53% of the Arctic drainage basin, and contribute major fluxes of water and material to the Arctic Ocean (Holmes et al , 2012Peterson et al 2002;Gordeev 2006;Wegner et al 2015). The remaining 47% of the Arctic drainage basin is characterized by smaller watersheds, where very limited flux estimates are available.…”

Collapsing Arctic coastlines

“…Coastal erosion rates as high as 25 m yr -1 (refs 2,3) together with the large amount of organic matter frozen in permafrost 4,5 are resulting in an annual release of 14.0 Tg (10 12 grams) of particulate organic carbon into the nearshore zone 6,7 . This carbon flux is in the same order of magnitude as the yearly contribution from all Arctic rivers, or the vertical net methane (CH 4 ) emissions from terrestrial permafrost 8 .…”