Seasonal to mesoscale variability of water masses and atmospheric conditions in Barrow Canyon, Chukchi Sea

Pickart, Robert S.; Nobre, Carolina; Lin, Peigen; Arrigo, Kevin R.; Ashjian, Carin J.; Berchok, Catherine L.; Cooper, Lee W.; Grebmeier, Jacqueline M.; Hartwell, Ian; He, Jianfeng; Itoh, Motoyo; Kikuchi, Takashi; Nishino, Shigeto; Vagle, Svein

doi:10.1016/j.dsr2.2019.02.003

Cited by 43 publications

(83 citation statements)

References 49 publications

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“…This is likely because of local water mass transformation on the shelf via air‐sea interaction that has reached the bottom due to wind mixing (October is the start of storm season, see Lin, Pickart, Moore, et al, ). This is consistent with the results of Pickart et al () who presented evidence of the conversion of ACW to BSW in October in Barrow Canyon. Although there are limited data in October, some ACW is present to the east of Barrow Canyon near the outer shelf.…”

Section: Progression and Evolution Of Water Massessupporting

confidence: 93%

Water Mass Evolution and Circulation of the Northeastern Chukchi Sea in Summer: Implications for Nutrient Distributions

et al. 2019

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Synoptic and historical shipboard data, spanning the period 1981–2017, are used to investigate the seasonal evolution of water masses on the northeastern Chukchi shelf and quantify the circulation patterns and their impact on nutrient distributions. We find that Alaskan coastal water extends to Barrow Canyon along the coastal pathway, with peak presence in September, while the Pacific Winter Water (WW) continually drains off the shelf through the summer. The depth‐averaged circulation under light winds is characterized by a strong Alaskan Coastal Current (ACC) and northward flow through Central Channel. A portion of the Central Channel flow recirculates anticyclonically to join the ACC, while the remainder progresses northeastward to Hanna Shoal where it bifurcates around both sides of the shoal. All of the branches converge southeast of the shoal and eventually join the ACC. The wind‐forced response has two regimes: In the coastal region the circulation depends on wind direction, while on the interior shelf the circulation is sensitive to wind stress curl. In the most common wind‐forced state—northeasterly winds and anticyclonic wind stress curl—the ACC reverses, the Central Channel flow penetrates farther north, and there is mass exchange between the interior and coastal regions. In September and October, the region southeast of Hanna Shoal is characterized by elevated amounts of WW, a shallower pycnocline, and higher concentrations of nitrate. Sustained late‐season phytoplankton growth spurred by this pooling of nutrients could result in enhanced vertical export of carbon to the seafloor, contributing to the maintenance of benthic hotspots in this region.

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Section: Progression and Evolution Of Water Massessupporting

confidence: 93%

Water Mass Evolution and Circulation of the Northeastern Chukchi Sea in Summer: Implications for Nutrient Distributions

et al. 2019

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“…Assessing 2011 and 2012 surface observations in T ‐ S and O 2 space (Figure ) allows some additional insight. Here we adopt water mass classifications following Pickart et al () to aid our interpretations. First, the reduced presence of sea ice melt‐influenced water (MW) in 2011 compared to 2012, as noted by Weingartner et al () and described above, is apparent.…”

Section: Spatial and Temporal Trends In Net Biological Production Fromentioning

confidence: 99%

“…In all panels data from the northern Bering/southern Chukchi, N. Chukchi, and W. Beaufort are represented by triangles, circles, and squares, respectively. Water masses as defined by Pickart et al () are indicated by boxes with thick gray lines: MW = meltwater, ACW = Alaska Coastal Water, BSW = Bering Summer Water, WW = remnant winter water. WW is formed during the winter by convective mixing over the shelf and is subsequently warmed by mixing and heating throughout the summer (Pickart et al, ).…”

Section: Spatial and Temporal Trends In Net Biological Production Fromentioning

confidence: 99%

“…Water masses as defined by Pickart et al () are indicated by boxes with thick gray lines: MW = meltwater, ACW = Alaska Coastal Water, BSW = Bering Summer Water, WW = remnant winter water. WW is formed during the winter by convective mixing over the shelf and is subsequently warmed by mixing and heating throughout the summer (Pickart et al, ). WW is typically associated with bottom waters beneath the pycnocline in the NE Chukchi during summer.…”

Section: Spatial and Temporal Trends In Net Biological Production Fromentioning

confidence: 99%

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Significant Biologically Mediated CO₂ Uptake in the Pacific Arctic During the Late Open Water Season

Juranek

Takahashi

Mathis³

et al. 2019

JGR Oceans

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Shifting baselines in the Arctic atmosphere‐sea ice‐ocean system have significant potential to alter biogeochemical cycling and ecosystem dynamics. In particular, the impact of increased open water duration on lower trophic level productivity and biological CO2 sequestration is poorly understood. Using high‐resolution observations of surface seawater dissolved O2/Ar and pCO2 collected in the Pacific Arctic in October 2011 and 2012, we evaluate spatial variability in biological metabolic status (autotrophy vs heterotrophy) as constrained by O2/Ar saturation (∆O2/Ar) as well as the relationship between net biological production and the sea‐air gradient of pCO2 (∆pCO2). We find a robust relationship between ∆pCO2 and ∆O2/Ar (correlation coefficient of −0.74 and −0.61 for 2011 and 2012, respectively), which suggests that biological production in the late open water season is an important determinant of the air‐sea CO2 gradient at a timeframe of maximal ocean uptake for CO2 in this region. Patchiness in biological production as indicated by ∆O2/Ar suggests spatially variable nutrient supply mechanisms supporting late season growth amidst a generally strongly stratified and nutrient‐limited condition.

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“…Weingartner et al, ; Woodgate et al, ). Furthermore, hydrographic surveys have revealed that winter water is still present within the pathways on the northern portion of the shelf in the early summer (Gong & Pickart, ; Pickart et al, ) and exiting the shelf via Barrow Canyon in late summer (Pickart et al, ). However, the extent to which the cold water is present outside of these pathways—prior to summer—has yet to be determined.…”

Section: Introductionmentioning

confidence: 99%

Characteristics and Transformation of Pacific Winter Water on the Chukchi Sea Shelf in Late Spring

et al. 2019

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Data from a late spring survey of the northeast Chukchi Sea are used to investigate various aspects of newly ventilated winter water (NVWW). More than 96% of the water sampled on the shelf was NVWW, the saltiest (densest) of which tended to be in the main flow pathways on the shelf. Nearly all of the hydrographic profiles on the shelf displayed a two‐layer structure, with a surface mixed layer and bottom boundary layer separated by a weak density interface (on the order of 0.02 kg/m3). Using a polynya model to drive a one‐dimensional mixing model, it was demonstrated that, on average, the profiles would become completely homogenized within 14–25 hr when subjected to the March and April heat fluxes. A subset of the profiles would become homogenized when subjected to the May heat fluxes. Since the study domain contained numerous leads within the pack ice—many of them refreezing—and since some of the measured profiles were vertically uniform in density, this suggests that NVWW is formed throughout the Chukchi shelf via convection within small openings in the ice. This is consistent with the result that the salinity signals of the NVWW along the central shelf pathway cannot be explained solely by advection from Bering Strait or via modification within large polynyas. The local convection would be expected to stir nutrients into the water column from the sediments, which explains the high nitrate concentrations observed throughout the shelf. This provides a favorable initial condition for phytoplankton growth on the Chukchi shelf.

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Seasonal to mesoscale variability of water masses and atmospheric conditions in Barrow Canyon, Chukchi Sea

Cited by 43 publications

References 49 publications

Water Mass Evolution and Circulation of the Northeastern Chukchi Sea in Summer: Implications for Nutrient Distributions

Water Mass Evolution and Circulation of the Northeastern Chukchi Sea in Summer: Implications for Nutrient Distributions

Significant Biologically Mediated CO₂ Uptake in the Pacific Arctic During the Late Open Water Season

Characteristics and Transformation of Pacific Winter Water on the Chukchi Sea Shelf in Late Spring

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Seasonal to mesoscale variability of water masses and atmospheric conditions in Barrow Canyon, Chukchi Sea

Cited by 43 publications

References 49 publications

Water Mass Evolution and Circulation of the Northeastern Chukchi Sea in Summer: Implications for Nutrient Distributions

Water Mass Evolution and Circulation of the Northeastern Chukchi Sea in Summer: Implications for Nutrient Distributions

Significant Biologically Mediated CO2 Uptake in the Pacific Arctic During the Late Open Water Season

Characteristics and Transformation of Pacific Winter Water on the Chukchi Sea Shelf in Late Spring

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Significant Biologically Mediated CO₂ Uptake in the Pacific Arctic During the Late Open Water Season