Interannual variability of surface and bottom sediment transport on the Laptev Sea shelf during summer

Abstract

Sediment transport dynamics were studied during ice-free conditions under different atmospheric circulation regimes on the Laptev Sea shelf (Siberian Arctic). To study the interannual variability of suspended particulate matter (SPM) dynamics and their coupling with the variability in surface river water distribution on the Laptev Sea shelf, detailed oceanographic, optical (turbidity and Ocean Color satellite data), and hydrochemical (nutrients, SPM, stable oxygen isotopes) process studies were carried out continuously during the summers of 2007 and 2008. Thus, for the first time SPM and nutrient variations on the Laptev Sea shelf under different atmospheric forcing and the implications for the turbidity and transparency of the water column can be presented. <br><br> The data indicate a clear link between different surface distributions of riverine waters and the SPM transport dynamics within the entire water column. The summer of 2007 was dominated by shoreward winds and an eastward transport of riverine surface waters. The surface SPM concentration on the southeastern inner shelf was elevated, which led to decreased transmissivity and increased light absorption. Surface SPM concentrations in the central and northern Laptev Sea were comparatively low. However, the SPM transport and concentration within the bottom nepheloid layer increased considerably on the entire eastern shelf. The summer of 2008 was dominated by offshore winds and northward transport of the river plume. The surface SPM transport was enhanced and extended onto the mid-shelf, whereas the bottom SPM transport and concentration was diminished. This study suggests that the SPM concentration and transport, in both the surface and bottom nepheloid layers, are associated with the distribution of riverine surface waters which are linked to the atmospheric circulation patterns over the Laptev Sea and the adjacent Arctic Ocean during the open water season. A continuing trend toward shoreward winds, weaker stratification and higher SPM concentration throughout the water column might have severe consequences for the ecosystem on the Laptev Sea shelf

From Fresh to Marine Waters: Characterization and Fate of Dissolved Organic Matter in the Lena River Delta Region, Siberia

“…The propagation of the plume along the Laptev Sea shelf has also induced the establishment of a strong frontal system in the NW part of our study area (see Figure 1). Such hydrographic characteristics were previously described as offshore wind conditions, when the predominant winds from the continent drive the offshore propagation of the Lena waters generating a strong stratification and a frontal system NW of the Lena Delta region (Bauch et al, 2009;Wegner et al, 2013). Thus, we have identified the presence of two hydrographic provinces within the sampled area: the plume-and marine-influenced sites (see Figure 1).…”

“…It contributes approximately 20% to the total fresh water discharge into the Arctic Ocean through its delta into the Laptev Sea (Cauwet and Sidorov, 1996). The Lena Delta and the Laptev Sea inner shelf encompass a large, shallow environment characterized by pronounced physical-chemical gradients (Bauch et al, 2009;Fofonova et al, 2014) and considerable amounts of sediments, dissolved, and particulate organic matter over the water column (Semiletov et al, 2011;Vonk et al, 2012Vonk et al, , 2014Wegner et al, 2013;Heim et al, 2014;Sánchez-García et al, 2014). Eastern Siberia (including the Lena River and its delta) is known to be affected by global warming with a thawing permafrost (Yang et al, 2002;Schuur et al, 2008), which subsequently affects the fresh water discharge, the production of DOM in river catchments and the riverine transport of organic material input into the shelf seas (Frey and McClelland, 2009;Lyon and Destouni, 2010;Semiletov et al, 2012Semiletov et al, , 2013Vonk et al, 2012Vonk et al, , 2014Sánchez-García et al, 2014;Fedorova et al, 2015).…”

Halocline water modification and along-slope advection at the Laptev Sea continental margin

“…Our measurement precision for all presented δ 18 O is at least ±0.04 ‰ (Bauch et al, , 2011a(Bauch et al, , b, 2013. All H 18 2 O/H 16 2 O ratios were calibrated with a VSMOW standard and reported in the usual δ-notation (Craig, 1961 Bauch et al (2011a).…”

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

“…Today, shelf currents experience a strong seasonality with wind and ice as limiting factors (e.g., Harms & Karcher 1999;McClimans et al 2000;Sternberg et al 2001;Wegner et al 2005;Schulze & Pickart 2012). The surface distribution of riverine water and river-derived material shows strong interannual variability, mainly attributed to atmospheric vorticity variations over the adjacent Arctic Ocean in summer (Guay et al 2001;Macdonald et al 2002; ViscosiShirley et al 2003;Dmitrenko et al 2005; Bauch et al 2009;Yamamoto-Kawai et al 2009;Wegner et al 2013). On the shelves and slopes, at water depth below 100 m, currents do not show a seasonal cycle (e.g., Woodgate et al 2001).…”