Deep water circulation and composition in the Arctic Ocean by dissolved barium, aluminium and silicate

Abstract

As part of the ARK-XXII/2 Polarstern expedition in summer 2007, dissolved Ba was analyzed in the Eurasian Basins and the Makarov Basin including the Alpha and Mendeleyev Ridges as well as on the adjacent shelves. The data was compared with data of dissolved Al and Si from the same cruise. Superimposed on the gradual increase of concentration with depth by dissolution of the particle rain, we observe different flow patterns in intermediate waters along the track. In the Atlantic and Intermediate Depth Water (AIDW) in the Amundsen Basin the influence from Eurasian shelf water can be seen in slightly enhanced concentrations of dissolved Ba compared with Al and Si. At the same time Al concentrations decrease with distance from the Eurasian shelves. Source waters to the Atlantic Layer Water (ALW) in the Makarov Basin have the same background Ba concentrations as the Nansen AIDW. We describe the distributions of the elements in the Deep Eurasian and Bottom Water (DEBW) by deep shelf convection as well as diffusion from sediments controlling concentrations in the Nansen DEBW while in the Amundsen DEBW diffusion from sediments appears to be more important. In the Makarov Basin inflow from the Canadian Basin and overflow from the Amundsen Basin at 2000 m depth at the Lomonosov Ridge are required to explain the composition of bottom waters.

Changes in Circulation and Particle Scavenging in the Amerasian Basin of the Arctic Ocean over the Last Three Decades Inferred from the Water Column Distribution of Geochemical Tracers

“…Intrusions of CB deep waters into the MB could also explain the warmer and saltier water observed in the bottom waters at the MB and Mendeleev Ridge stations after 2000 (insets in the θ‐S plots in Figures b–c). Nonetheless, considering the gradual decrease of tracer—especially 231 Pa d —concentrations with depth below 3,000 m, coupled to a gradual increase of dissolved O 2 (Figures b and c), we agree with Middag et al () and Roeske et al () that MB bottom water is also made of some colder and fresher Amundsen Basin Deep Water (ABDW) that likely came over the Lomonosov Ridge (between 2,000 and 2,500 m) and sank due to its higher density than the local bottom waters (Timmermans et al, ).…”

“…Hydrological features such as the θ-S convexity and O 2 minimum observed within the DTL at the MB stations also support exchanges of CB deep waters toward the MB (Figures 4, 5h, and 9d). Although the direction of exchanges we suggest here conflicts with former hydrological study conclusions that invoked a dominant flux of DTL water above the Mendeleev/Alpha Ridge from the MB toward the CB (e.g., Carmack et al, 2012;Rudels, 2009), Swift et al (1997) (Figures 9b and 12c), we agree with Middag et al (2009) and Roeske et al (2012) that MB bottom water is also made of some colder and fresher Amundsen Basin Deep Water (ABDW) that likely came over the Lomonosov Ridge (between 2,000 and 2,500 m) and sank due to its higher density than the local bottom waters (Timmermans et al, 2005).…”

Dissolved iron in the Arctic Ocean: Important role of hydrothermal sources, shelf input and scavenging removal

“…Also, in the deep waters (MBDW and EBDW), we did not observe a significant positive correlation between DFe and Si (or (NO 3 + NO 2 )). However, these waters display a strong input of terrestrial material [ Middag et al , 2009; Roeske et al , 2012], diminishing a possible biogenic particle remineralisation signal.…”

Dissolved Fe in the Deep and Upper Arctic Ocean With a Focus on Fe Limitation in the Nansen Basin

“…The TPD track and relative contributions of the different shelf seas is known to vary with the Arctic Oscillation index (Macdonald et al, 2005). Surface concentrations of DFe inside the TPD are expected to be dictated by a strong riverine influence (Bauch et al, 2011;Klunder et al, 2012a;Roeske et al, 2012;Rutgers van der Loeff et al, 2012;Slagter et al, 2017). One major impact of climate change is the thaw of permafrost soil (Stedmon et al, 2011;Schuur et al, 2015) resulting in an increase in DOM released into the Arctic Ocean (Vonk et al, 2012(Vonk et al, , 2013.…”