Fram Strait sea-ice sediment provinces based on silt and clay compositions identify Siberian Kara and Laptev seas as main source regions

Dethleff, Dirk; Kuhlmann, Gesa

doi:10.3402/polar.v29i3.6070

Cited by 6 publications

(13 citation statements)

References 52 publications

(61 reference statements)

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“…The progressive loss of sea ice may further increase export of redox‐sensitive micronutrients such as dMn and dCo in response to enhanced photo‐dissolution and solubilization processes in the surface ocean (Moffett & Ho, 1996; Sunda & Huntsman, 1994). Although, conversely, increases in Arctic primary production in response to reductions in summertime sea ice cover (Ardyna et al., 2014; Arrigo & van Dijken, 2015) may increase the demand for micronutrients within the Arctic, and also decrease sediment and micronutrient transport associated with advection of sea ice (Marsay et al., 2018; Measures, 1999) towards Fram Strait (Dethleff & Kuhlmann, 2010).…”

Section: Conclusion and Future Perspectivesmentioning

confidence: 99%

Arctic – Atlantic Exchange of the Dissolved Micronutrients Iron, Manganese, Cobalt, Nickel, Copper and Zinc With a Focus on Fram Strait

Krisch

Hopwood

Roig

et al. 2022

Global Biogeochemical Cycles

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The Arctic Ocean is considered a source of micronutrients to the Nordic Seas and the North Atlantic Ocean through the gateway of Fram Strait (FS). However, there is a paucity of trace element data from across the Arctic Ocean gateways, and so it remains unclear how Arctic and North Atlantic exchange shapes micronutrient availability in the two ocean basins. In 2015 and 2016, GEOTRACES cruises sampled the Barents Sea Opening (GN04, 2015) and FS (GN05, 2016) for dissolved iron (dFe), manganese (dMn), cobalt (dCo), nickel (dNi), copper (dCu) and zinc (dZn). Together with the most recent synopsis of Arctic-Atlantic volume fluxes, the observed trace element distributions suggest that FS is the most important gateway for Arctic-Atlantic dissolved micronutrient exchange as a consequence of Intermediate and Deep Water transport. Combining fluxes from FS and the Barents Sea Opening with estimates for Davis Strait (GN02, 2015) suggests an annual net southward flux of 2.7 ± 2.4 Gg•a −1 dFe, 0.3 ± 0.3 Gg•a −1 dCo, 15.0 ± 12.5 Gg•a −1 dNi and 14.2 ± 6.9 Gg•a −1 dCu from the Arctic toward the North Atlantic Ocean. Arctic-Atlantic exchange of dMn and dZn were more balanced, with a net southbound flux of 2.8 ± 4.7 Gg•a −1 dMn and a net northbound flux of 3.0 ± 7.3 Gg•a −1 dZn. Our results suggest that ongoing changes to shelf inputs and sea ice dynamics in the Arctic, especially in Siberian shelf regions, affect micronutrient availability in FS and the high latitude North Atlantic Ocean. Plain Language SummaryRecent studies have proposed that the Arctic Ocean is a source of micronutrients such as dissolved iron (dFe), manganese (dMn), cobalt (dCo), nickel (dNi), copper (dCu) and zinc (dZn) to the North Atlantic Ocean. However, data at the Arctic Ocean gateways including Fram Strait and the Barents Sea Opening have been missing to date and so the extent of Arctic micronutrient transport toward the Atlantic Ocean remains unquantified. Here, we show that Fram Strait is the most important gateway for Arctic-Atlantic micronutrient exchange which is a result of deep water transport at depths >500 m. Combined with a flux estimate for Davis Strait, this study suggests that the Arctic Ocean is a net source of dFe, dNi and dCu, and possibly also dCo, toward the North Atlantic Ocean. Arctic-Atlantic dMn and dZn exchange seems more balanced. Properties in the East Greenland Current showed substantial similarities to observations in the upstream Central Arctic Ocean, indicating that Fram Strait may export micronutrients from Siberian riverine discharge and shelf sediments >3,000 km away. Increasing Arctic river discharge, permafrost thaw and coastal erosion, all consequences of ongoing climate change, may therefore alter future Arctic Ocean micronutrient transport to the North Atlantic Ocean.

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Section: Conclusion and Future Perspectivesmentioning

confidence: 99%

Arctic – Atlantic Exchange of the Dissolved Micronutrients Iron, Manganese, Cobalt, Nickel, Copper and Zinc With a Focus on Fram Strait

Krisch

Hopwood

Roig

et al. 2022

Global Biogeochemical Cycles

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“…Sediment‐laden sea ice, also referred to as dirty ice, is a common occurrence throughout coastal and offshore regions in the Arctic Ocean (Darby et al, ; Eicken et al, , , ; Nürnberg et al, ; Osterkamp & Gosink, ). Seafloor sediments are considered to be the dominant source of this entrained particulate matter (Measures, ; Lannuzel et al, , ; Dethleff & Kuhlmann, , ; Darby et al, ). Sediment incorporated into sea ice is transported with ice drift and released into the ocean during ice melt.…”

Section: Introductionmentioning

confidence: 99%

“…Suspension freezing is considered to occur mainly during fall freeze‐up of shallow water regions (Campbell & Collin, ; Eicken et al, ; Reimnitz et al, ) and throughout the ice growth season in coastal polynyas (e.g. Eicken et al, ; Dethleff & Kuhlmann, , ). Coastal polynyas are of particular importance for sediment entrainment because (1) sea ice production is quite high over winter, (2) frazil ice can form in the water column as a result of wind and thermohaline mixing, (3) water depth is shallow, and hence, (4) frazil ice can easily interact with resuspended sediment.…”

Section: Introductionmentioning

confidence: 99%

Favorable Conditions for Suspension Freezing in an Arctic Coastal Polynya

et al. 2019

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Arctic sea ice incorporates and transports sediment, releasing it back into the water column during the melting season. This process constitutes an important aspect of marine sediment transport and biogeochemical cycling. Sediment incorporation into sea ice is considered to occur mainly through underwater interaction between frazil ice and resuspended sediment, referred to as suspension freezing. However, harsh environmental conditions have greatly limited field observations of this phenomenon. Analysis of mooring data from a coastal polynya in the northeastern Chukchi Sea, in conjunction with coastal ice radar and meteorological data, indicates that suspension freezing is a key mechanism for sediment entrainment into sea ice. During polynya episodes, acoustic backscatter data obtained by an Acoustic Doppler Current Profiler showed the presence of frazil ice from the surface down to 20-to 25-m depth, coinciding with in situ and potential supercooling. Underwater frazil ice persisted over 1 week under windy, turbulent water column conditions. A combination of the turbidity and Acoustic Doppler Current Profiler backscatter data revealed upward sediment dispersion associated with strong currents during the polynya episodes. The fact that frazil ice and resuspended sediment were detected at the same depth and time strongly suggests the interaction between ice crystals and sediment particles, that is, suspension freezing.Plain Language Summary Sea ice incorporates, transports, and releases particulate matter.These processes constitute an important aspect of the biology, biogeochemical cycling, and pollutant transport in polar oceans. Seafloor sediments serve as the most important source of such particulate matter; however, the process of sediment incorporation into sea ice remains poorly explored. We conducted a year-long study of sediment resuspension and entrainment processes, using underwater sensors deployed in the Chukchi Sea. During winter, wind-driven offshore transport of sea ice created area of open water and newly grown thin ice that persisted for several days, so-called coastal polynya or flaw lead system. Our sensors recorded small ice crystals, so-called frazil ice, that formed in the water column when water temperatures were below freezing point (supercooling). During some of these episodes, sediment was resuspended from the seafloor and dispersed upward by the strong currents, bringing it into water depths at which frazil ice was encountered. Such conditions provide for opportunities that allow frazil ice crystals or aggregates to capture resuspended sediment, a process referred to as suspension freezing. Based on this study, we propose that suspension freezing commonly occurs in shallow Arctic polynyas, serving as a key process of sediment incorporation into sea ice.

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“…These observations indicate that the sediment entrainment into sea ice is related to new ice formation. Dethleff and Kuhlmann [] reported that the texture and composition of the material found inside the sea ice collected from land‐fast ice adjacent to a lead coincide with those of the bottom sediment in the Kara Sea. They concluded that a major source for material inside sea ice is the bottom sediment entrained into sea ice through suspension freezing.…”

Section: Introductionmentioning

confidence: 99%

Observations of frazil ice formation and upward sediment transport in the Sea of Okhotsk: A possible mechanism of iron supply to sea ice

Ito

Ohshima

Fukamachi

et al. 2017

J. Geophys. Res. Oceans

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In the Sea of Okhotsk, sediment incorporation, transport and release by sea ice potentially plays important roles in the bio‐related material (such as iron) cycle and ecosystem. The backscatter strength data of bottom‐mounted Acoustic Doppler Current Profilers have suggested signals of frazil ice down to 30 m depth, and signals of upward sediment transport throughout the water column simultaneously in the region northeast of Sakhalin, with a water depth of ∼100 m. Such events occurred under turbulent conditions with strong winds of 10–20 m s−1. During such events, newly formed ice was present near the observational sites, shown by satellite microwave imagery. Sediment dispersion from the bottom occurred in association with strong currents of 1.0–1.5 m s−1. During these events, the mixed layer reaches near the bottom due to wind‐induced stirring, inferred from the high frequency component of vertical velocity. Thus the winter time turbulent mixing brings re‐suspended sediment up to near the ocean surface. This study provides the first observational evidence of a series of processes on the incorporation of sedimentary materials into sea ice: sedimentary particles are dispersed by the strong bottom current, subsequently brought up to near the surface by winter time mixing, and finally incorporated into sea ice through underwater interaction with frazil ice and/or flooding of sea ice floes. This wintertime incorporation of bottom sediment into sea ice is a possible mechanism of iron supply to sea ice which melts in spring, and releases bio‐reactive iron into the ocean.

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Fram Strait sea-ice sediment provinces based on silt and clay compositions identify Siberian Kara and Laptev seas as main source regions

Cited by 6 publications

References 52 publications

Arctic – Atlantic Exchange of the Dissolved Micronutrients Iron, Manganese, Cobalt, Nickel, Copper and Zinc With a Focus on Fram Strait

Arctic – Atlantic Exchange of the Dissolved Micronutrients Iron, Manganese, Cobalt, Nickel, Copper and Zinc With a Focus on Fram Strait

Favorable Conditions for Suspension Freezing in an Arctic Coastal Polynya

Observations of frazil ice formation and upward sediment transport in the Sea of Okhotsk: A possible mechanism of iron supply to sea ice

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