Origin of freshwater and polynya water in the Arctic Ocean halocline in summer 2007

Bauch, Dorothea; Loeff, Michiel M. Rutgers van der; Andersen, Nils; Torres-Valdés, Sinhue; Bakker, Karel; Abrahamsen, E. Povl

doi:10.1016/j.pocean.2011.07.017

Cited by 92 publications

(207 citation statements)

References 52 publications

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“…An overview of the elemental dissolved Ba distribution in the surface water layer of the sections is seen in figures 3-7a. Additional panels on water mass fractions together with T pot and salinity are displayed in Bauch et al (2011a). Potential temperature and salinity data are courtesy of the oceanography group of ARKXXII/2 (Schauer, 2008).…”

Section: Resultsmentioning

confidence: 99%

“…For further details on the fraction calculation refer also to Bauch et al (2011a). If the resulting fraction of Pacific water is negative (because of vanishingly small quantities of Pacific water combined with small inaccuracies in end-members and measurements), a three-component system of equations is solved instead, only using eqns.…”

Section: Balancing the Fresh Water Fraction In The Upper Water Columnmentioning

confidence: 99%

“…While this is largely true under the winter sea ice cover, the Arctic Ocean is partly free of sea ice in summer and ice-free areas were especially large in summer 2007. Exchange of dissolved O 2 with the atmosphere may lead to an underestimation of f p in the summer mixed layer (Bauch et al, 2011a). Bauch et al (2011a) thus additionally follow the procedure based on N/P presented by Jones et al (1998; and Yamamoto-Kawai et al (2008) using the "pure Pacific water" correlation line [NO x ] = 15.314· [PO 4 ] -14.395 (Jones et al, 2008) and an adjusted "pure Atlantic water" correlation line (Bauch et al, 2011a) [NO x ] = 16.785· [PO 4 ] -1.9126.…”

Section: Balancing the Fresh Water Fraction In The Upper Water Columnmentioning

confidence: 99%

“…Exchange of dissolved O 2 with the atmosphere may lead to an underestimation of f p in the summer mixed layer (Bauch et al, 2011a). Bauch et al (2011a) thus additionally follow the procedure based on N/P presented by Jones et al (1998; and Yamamoto-Kawai et al (2008) using the "pure Pacific water" correlation line [NO x ] = 15.314· [PO 4 ] -14.395 (Jones et al, 2008) and an adjusted "pure Atlantic water" correlation line (Bauch et al, 2011a) [NO x ] = 16.785· [PO 4 ] -1.9126. On the other hand denitrification creates an apparent f p signal and Bauch et al (2011a) use the brine signal (negative fi) to identify this apparent f p within the Transpolar Drift.…”

Section: Balancing the Fresh Water Fraction In The Upper Water Columnmentioning

confidence: 99%

“…The high salinity fraction can be divided in Atlantic and Pacific fractions by using initial phosphate corrected for mineralization with oxygen (PO 4 *) (Broecker, 1985;Ekwurzel et al, 2001). Alternatively N/P ratios can be used to identify fractions of Atlantic or Pacific origin (Yamamoto-Kawai et al, 2008;Bauch et al, 2011a). Dissolved Ba was described previously as a powerful quasi-conservative tracer for Arctic water masses (Falkner et al, 1994;Guay and Falkner, 1998b;Taylor et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

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Utility of dissolved barium in distinguishing North American from Eurasian runoff in the Arctic Ocean

et al. 2012

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Dissolved barium has been shown to have the potential to distinguish Eurasian from North American (NA) river runoff. As part of the ARK-XXII/2 Polarstern expedition in summer 2007, Ba was analyzed in the Barents, Kara, Laptev seas, and the Eurasian Basins as well as the Makarov Basin up to the Alpha and Mendeleyev Ridges. By combining salinity, δ 18 O and initial phosphate corrected for mineralization with oxygen (PO 4 *) or N/P ratios we identified the water mass fractions of meteoric water, sea ice meltwater, and marine waters of Atlantic as well as Pacific origin in the upper water column. In all basins inside the lower halocline layer and the Arctic intermediate waters we find Ba concentrations close to those of the Fram Strait branch of the lower halocline (41-45 nM), reflecting the composition of the incoming Atlantic water. A layer of upper halocline water (UHW) with higher Ba concentrations (45-55 nM) is identified in the Makarov Basin. Atop of the UHW, the Surface Mixed Layer (SML), including the summer and winter mixed layers, has high concentrations of Ba (58-67 nM). In the SML of the investigated area of the central Arctic the meteoric fraction can be identified by assuming a conservative behavior of Ba to be primarily of Eurasian river origin. However, in productive coastal regions biological removal compromises the use of Ba to distinguish between Eurasian and NA rivers. As a consequence, the NA river water fraction is underestimated in productive surface waters or waters that have passed a productive region, whereas this fraction is overestimated in subsurface waters containing remineralised Ba, particularly when these waters have passed productive shelf regions. Especially in the Laptev Sea and small regions in the Barents Sea, Ba concentrations are low in surface waters. In the Laptev Sea exceptionally high Ba concentrations in shelf bottom waters indicate that Ba is removed from surface waters to deep waters by biological activity enhanced by increasing ice-free conditions as well as by scavenging by organic matter of terrestrial origin. We interpret high Ba concentrations in the UHW of the Makarov Basin to result from enrichment by remineralisation in bottom waters on the shelf of the Chukchi Sea and therefore the calculated NA runoff is an artefact. We conclude that no NA runoff can be demonstrated unequivocally anywhere during our expedition with the set of tracers considered here. Small contributions of NA runoff may have been masked by Ba depletion and could only be resolved by supportive tracers on the uptake history. We thus suggest that Ba has to be used with care as it can put limits but not yield quantitative water mass distributions. Only if the extra Ba inputs exceed the cumulative biological uptake the signal can be unequivocally attributed to NA runoff.

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Section: Resultsmentioning

confidence: 99%

Section: Balancing the Fresh Water Fraction In The Upper Water Columnmentioning

confidence: 99%

Section: Balancing the Fresh Water Fraction In The Upper Water Columnmentioning

confidence: 99%

Section: Balancing the Fresh Water Fraction In The Upper Water Columnmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Utility of dissolved barium in distinguishing North American from Eurasian runoff in the Arctic Ocean

et al. 2012

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The influence of sea ice cover on air-sea gas exchange estimated with radon-222 profiles

Loeff

Cassar

Nicolaus

et al. 2014

J. Geophys. Res. Oceans

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Air-sea gas exchange plays a key role in the cycling of greenhouse and other biogeochemically important gases. Although air-sea gas transfer is expected to change as a consequence of the rapid decline in summer Arctic sea ice cover, little is known about the effect of sea ice cover on gas exchange fluxes, especially in the marginal ice zone. During the Polarstern expedition ARK-XXVI/3 (TransArc, August/September 2011) to the central Arctic Ocean, we compared 222 Rn/ 226 Ra ratios in the upper 50 m of 14 ice-covered and 4 ice-free stations. At three of the ice-free stations, we find 222 Rn-based gas transfer coefficients in good agreement with expectation based on published relationships between gas transfer and wind speed over open water when accounting for wind history from wind reanalysis data. We hypothesize that the low gas transfer rate at the fourth station results from reduced fetch due to the proximity of the ice edge, or lateral exchange across the front at the ice edge by restratification. No significant radon deficit could be observed at the ice-covered stations. At these stations, the average gas transfer velocity was less than 0.1 m/d (97.5% confidence), compared to 0.5-2.2 m/d expected for open water. Our results show that air-sea gas exchange in an ice-covered ocean is reduced by at least an order of magnitude compared to open water. In contrast to previous studies, we show that in partially ice-covered regions, gas exchange is lower than expected based on a linear scaling to percent ice cover.

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Variability in the meteoric water, sea‐ice melt, and Pacific water contributions to the central Arctic Ocean, 2000–2014

2015

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Fourteen years (2000Fourteen years ( -2014 of bottle chemistry data collected during the North Pole Environmental Observatory were compiled to examine variations in the composition of freshwater (meteoric water, net sea-ice meltwater, and Pacific water) over mixed layer of the Central Arctic Ocean. In addition to significant spatial and interannual variability, there was a general decrease in meteoric water (MW) fractions at the majority of stations reoccupied over the duration of the program that was approximately balanced by a concomitant increase in freshwater from sea-ice melt (SIM FW) between 2000 and 2012. Inventories (0-120 m) of MW and SIM FW computed using available data between 2005 and 2012 exhibited similar variations over the study area, allowing for first-order estimates of the mean annual changes in MW (2389 6 194 km 3 yr 21 ) and SIM FW (292 6 97 km 3 yr 21) for the Central Arctic region. These mean annual changes were attributed to the diversion of Siberian river runoff to the Beaufort Gyre and the overall reduction of sea ice volume across the Arctic, respectively. In addition to this lower-frequency variability, spatial gradients and interannual variations in MW, SIM FW, and Pacific water contributions to specific locations were attributed to shifts in the Transpolar Drift that advects waters of eastern and western Arctic origin through the study area.

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Origin of freshwater and polynya water in the Arctic Ocean halocline in summer 2007

Cited by 92 publications

References 52 publications

Utility of dissolved barium in distinguishing North American from Eurasian runoff in the Arctic Ocean

Utility of dissolved barium in distinguishing North American from Eurasian runoff in the Arctic Ocean

The influence of sea ice cover on air-sea gas exchange estimated with radon-222 profiles

Variability in the meteoric water, sea‐ice melt, and Pacific water contributions to the central Arctic Ocean, 2000–2014

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