Particle sources and downward fluxes in the eastern Fram strait under the influence of the west Spitsbergen current

Abstract

The carbon cycle of the Arctic Ocean is tightly regulated by land–atmosphere–cryosphere–ocean inter- actions. Characterizing these environmental exchanges and feedbacks is critical to facilitate projections of the carbon cycle under changing climate conditions. The environmental drivers of sinking particles including organic carbon (OC) to the deep-sea floor are investigated with four moorings including se- diment traps and currentmeters at the Arctic gateway in the eastern Fram Strait, which is the area where warm anomalies are transported northwards to the Arctic. Particles fluxes were collected over one year (July 2010–July 2011) and have been analysed to obtain the content of the lithogenic fraction, calcium carbonate, OC and its stable isotopes, opal, and the grain size. Records of near bottom current speed and temperature along with satellite observations of sea ice extent and chlorophyll-a concentration have been used for evaluation of the environmental conditions.\ud We found increased lithogenic fluxes (up to 9872 mg m 2 d 1) and coarsening grain size of settling particles in late winter–early spring. At the same time, intensifications of the northward flowing west Spitsbergen current (WSC) were recorded. The WSC was able to resuspend and transport northwards sediments that were deposited at the outlet of Storfjordrenna and on the upper slope west of Spits- bergen. The signal of recurrent winnowing of fine particles was also detected in the top layer of surface sediments. In addition, an increased arrival of sea ice transported ice rafted detritus (4414 detrital carbonate mineral grains larger than 1 mm per m2) from the southern Spitsbergen coast along with terrestrial organic matter was observed beyond 1000 m of water depth during winter months. Finally, the downward particle fluxes showed typical temporal variability of high latitudes, with high percen- tages of the biogenic compounds (opal, organic carbon and calcium carbonate) linked to the phyto- plankton bloom in spring–summer. However, on an annual basis local planktonic production was a secondary source for the downward OC, since most of the OC was advected laterally by the WSC. Overall, these observations demonstrated the sensitivity of the downward flux of particles to environmental conditions such as hydrodynamics, sea ice rafting, and pelagic primary production. Future alteration of the patterns of natural drivers due to climate change is thus expected to cause major shifts in the downward flux of particles, including carbon, to the deep sea ecosystems

Organic Carbon Origin, Benthic Faunal Consumption, and Burial in Sediments of Northern Atlantic and Arctic Fjords (60–81°N)

“…A few mechanisms have been postulated to explain the high (compared even to other Svalbard fjords) contribution of land‐originated C org in Hornsund, including supplies from ornithogenic tundra enriched by large seabirds colonies dwelling in this fjord (Węsławski et al, ) or contribution of ancient organic matter originating from melting glaciers (Szczuciński, unpublished data of 14 C dating of C org in Brepollen, Hornsund glacial bay) in inner basin. However, similarly low δ 13 C (around −24‰) were also found in sediments on the shelf break off Hornsund and was interpreted as reflecting input of terrestrial matter transported by drift ice from the Barents Sea with East Spitsbergen Current (Sanchez‐Vidal et al, ).…”

Impact of Sea Ice on the Hydrodynamics and Suspended Sediment Concentration in the Coastal Waters of Qinhuangdao, China

“…To explore the similarities and differences in vertical distribution of velocity and SSC in different tidal phases during typical spring tide periods with or without sea ice, we first selected typical spring tide periods based on the changes in tidal current velocity at M1, along with the envelope curve (Figure 5c). These periods were February 2, 3, and 4 (with ice cover), and February 17,18,and 19 (without ice cover). We then performed regression analysis between the velocity and the height from the bottom, as well as between the backscatter intensity and the height from the bottom, in different tidal phases during these typical spring tide periods (high tide, ebb tide, and slack water).…”

“…Currently, sea ice research is concentrated in the polar regions [9][10][11][12] but is relatively scant in mid-latitude coastal waters [13][14][15]. Most sea ice studies obtain surface information, such as sea ice coverage area, coverage range, coverage time, and drift trajectory, through satellite remote sensing observations [16][17][18][19][20]. Owing to the limitations of objective conditions (e.g., the performance of instruments and batteries may be greatly reduced in extremely cold weather), very few long-term observations on in situ water bodies demonstrate the vertical hydrodynamic characteristics during sea ice coverage-for instance, the observation of mooring systems conducted by Boone et al in northeast Greenland from October 2013 to May 2014 [21].…”

Deep Flow Variability Offshore South-West Svalbard (Fram Strait)

“…There is a remarkable variability in the system due to several forcing mechanisms (e.g., atmospheric, internal, tidal, shelf dynamics) that play an important role, especially in the upper layer [5][6][7][8][9][10]. On the contrary, it is not completely clear which processes are responsible for the inter-annual and seasonal deep flow variability in the western offshore Spitsbergen region [11,12]. Several studies, using both experimental and numerical modelling approaches, have addressed the role of interactions between Atlantic Water (AW) carried by the West Spitsbergen Current (WSC, [10,11,[13][14][15][16]), and shelf and fjord waters [2,[17][18][19][20] in the observed variability.…”

“…On the contrary, it is not completely clear which processes are responsible for the inter-annual and seasonal deep flow variability in the western offshore Spitsbergen region [11,12]. Several studies, using both experimental and numerical modelling approaches, have addressed the role of interactions between Atlantic Water (AW) carried by the West Spitsbergen Current (WSC, [10,11,[13][14][15][16]), and shelf and fjord waters [2,[17][18][19][20] in the observed variability. Some of the processes that may be relevant for deep water circulation and variability in the western Spitsbergen region have been summarized in Figure 1.…”