Glacial Meltwater Identification in the Amundsen Sea

Biddle, Louise C.; Heywood, Karen J.; Kaiser, Jan; Jenkins, Adrian

doi:10.1175/jpo-d-16-0221.1

Cited by 42 publications

(85 citation statements)

References 46 publications

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“…This depth range is selected in order to compare values more easily with the hydrographic GMW content, which cannot be used in the upper 150 m due to atmospheric interaction and SIM (Jenkins, ). This shows high NG GMW content along the front of PIIS (4.95 m) and in stations to the west, surrounding Thwaites (4.07 m) and at the western end of the zonal section south of Burke Island, where values are all higher than 1.9 m. The higher concentrations of NG GMW content in these locations are as previously reported (Biddle et al., ; Nakayama et al., ) and follow expected current patterns associated with geostrophic currents in the region (Thurnherr et al., ; Wåhlin et al., ). However, our data also show nonnegligible quantities of GMW at the continental shelf edge with column inventories up to 1 m and mean values of 0.68 m. The central channel has mean column inventories of 0.77 m, similar to recent modeling studies (Nakayama et al., ).…”

Section: Distribution Of Gmw Using Noble Gasessupporting

confidence: 87%

“…This method is identical to the one used for hydrographic tracers (Θ, S A , c (O 2 )) by Biddle et al. (). OMPA uses a least squares regression with a nonnegativity constraint to solve the overdetermined equation:

((), \begin{matrix} center center centerarray \\ array χ_{1, mCDW} & array χ_{1, AEW} & array χ_{1, GMW} \\ array χ_{2, mCDW} & array χ_{2, AEW} & array χ_{2, GMW} \\ array ⋮ & array ⋮ & array ⋮ \\ array χ_{n, mCDW} & array χ_{n, AEW} & array χ_{n, GMW} \\ array 1 & array 1 & array 1 \end{matrix}) ((), \begin{matrix} centerarray \\ array F_{mCDW} \\ array F_{AEW} \\ array F_{GMW} \end{matrix}) = ((), \begin{matrix} centerarray \\ array χ_{1, obs} \\ array χ_{2, obs} \\ array ⋮ \\ array χ_{n, obs} \\ array 1 \end{matrix}),

where χ n , k is the noble gas tracer n of water mass k and F k is the water mass fraction.…”

Section: Distribution Of Gmw Using Noble Gasesmentioning

confidence: 99%

“…() discussed two variations of mCDW, namely, mCDW and pseudo‐CDW (pCDW). The pCDW endpoint refers to the precise properties on the mCDW‐WW mixing line that are able to flow underneath PIIS to cause ocean basal melt and is specific to each season's characeteristics as the thermocline shoals or deepens (Biddle et al., ; Webber et al., ). The Θ‐ S A ‐ c (O 2 ) mCDW endpoint will include GMW from different pCDW characteristics (Biddle et al., 2017).…”

Section: Gmw From Hydrographic Tracersmentioning

confidence: 99%

“…Recent work has shown that up to 500 km from PIIS, hydrographic tracers (conservative temperature, absolute salinity, and dissolved oxygen concentrations) identify possible GMW signatures (Biddle et al., ). However, these conservative tracers are affected by atmospheric exchange in the mixed layer and deeper in the water column by other water masses mixing in with the GMW.…”

Section: Introductionmentioning

confidence: 99%

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Upper Ocean Distribution of Glacial Meltwater in the Amundsen Sea, Antarctica

2019

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Pine Island Ice Shelf, in the Amundsen Sea, is losing mass due to increased heat transport by warm ocean water penetrating beneath the ice shelf and causing basal melt. Tracing this warm deep water and the resulting glacial meltwater can identify changes in melt rate and the regions most affected by the increased input of this freshwater. Here, optimum multiparameter analysis is used to deduce glacial meltwater fractions from independent water mass characteristics (standard hydrographic observations, noble gases, and oxygen isotopes), collected during a ship‐based campaign in the eastern Amundsen Sea in February–March 2014. Noble gases (neon, argon, krypton, and xenon) and oxygen isotopes are used to trace the glacial melt and meteoric water found in seawater, and we demonstrate how their signatures can be used to rectify the hydrographic trace of glacial meltwater, which provides a much higher‐resolution picture. The presence of glacial meltwater is shown to mask the Winter Water properties, resulting in differences between the water mass analyses of up to 4‐g/kg glacial meltwater content. This discrepancy can be accounted for by redefining the “pure” Winter Water endpoint in the hydrographic glacial meltwater calculation. The corrected glacial meltwater content values show a persistent signature between 150 and 400 m of the water column across all of the sample locations (up to 535 km from Pine Island Ice Shelf), with increased concentration toward the west along the coastline. It also shows, for the first time, the signature of glacial meltwater flowing off‐shelf in the eastern channel.

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Section: Distribution Of Gmw Using Noble Gasessupporting

confidence: 87%

((), \begin{matrix} center center centerarray \\ array χ_{1, mCDW} & array χ_{1, AEW} & array χ_{1, GMW} \\ array χ_{2, mCDW} & array χ_{2, AEW} & array χ_{2, GMW} \\ array ⋮ & array ⋮ & array ⋮ \\ array χ_{n, mCDW} & array χ_{n, AEW} & array χ_{n, GMW} \\ array 1 & array 1 & array 1 \end{matrix}) ((), \begin{matrix} centerarray \\ array F_{mCDW} \\ array F_{AEW} \\ array F_{GMW} \end{matrix}) = ((), \begin{matrix} centerarray \\ array χ_{1, obs} \\ array χ_{2, obs} \\ array ⋮ \\ array χ_{n, obs} \\ array 1 \end{matrix}),

where χ n , k is the noble gas tracer n of water mass k and F k is the water mass fraction.…”

Section: Distribution Of Gmw Using Noble Gasesmentioning

confidence: 99%

Section: Gmw From Hydrographic Tracersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Upper Ocean Distribution of Glacial Meltwater in the Amundsen Sea, Antarctica

2019

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“…Salinity gradually increased from surface to 1,040 m water. These vertical patterns of temperature and salinity revealed a typical hydrographic condition (e.g., three water masses; Antarctic Surface Water, Winter Water, and modified Circumpolar Deep Water) found in the Amundsen Sea during austral summer (Biddle et al, ; Dinniman et al, ; Yager et al, ). The Z p and Z m ranged from 11 to 19 m depth (mean = 13.0 ± 3.0 m) and 17 to 147 m depth (mean = 47.9 ± 46.2 m), respectively (Table ).…”

Section: Resultsmentioning

confidence: 81%

Vertical Distributions of Macromolecular Composition of Particulate Organic Matter in the Water Column of the Amundsen Sea Polynya During the Summer in 2014

Kim

Lee

et al. 2018

JGR Oceans

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Macromolecular compositions (carbohydrates, proteins, and lipids) of particulate organic matter (POM) are crucial as a basic marine food quality. To date, however, one investigation has been carried out in the Amundsen Sea. Water samples for macromolecular compositions were obtained at selected seven stations in the Amundsen Sea Polynya (AP) during the austral summer in 2014 to investigate vertical characteristics of POM. We found that a high proportion of carbohydrates (45.9 ± 11.4%) in photic layer which are significantly different from the previous result (27.9 ± 6.9%) in the AP, 2012. The plausible reason could be the carbohydrate content strongly associated with biomass of the dominant species (Phaeocystis antarctica). The calorific content of food material (FM) in the photic layer obtained in this study is similar with that of the Ross Sea as one of the highest primary productivity regions in the Southern Ocean. Total concentrations, calorific values, and calorific contents of FM were higher in the photic layer than the aphotic layer, which implies that a significant fraction of organic matter underwent degradation. A decreasing proteins/carbohydrates (PRT/CHO) ratio with depth could be caused by preferential nitrogen loss during sinking period. Since the biochemical compositions of POM mostly fixed in photic layers could play an important role in transporting organic carbon into the deep sea, further detail studies on the variations in biochemical compositions and main controlling factors are needed to understand sinking mechanisms of POM.

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Pathways and supply of dissolved iron in the Amundsen Sea (Antarctica)

et al. 2017

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Numerous coastal polynyas fringe the Antarctic continent and strongly influence the productivity of Antarctic shelf systems. Of the 46 Antarctic coastal polynyas documented in a recent study, the Amundsen Sea Polynya (ASP) stands out as having the highest net primary production per unit area. Incubation experiments suggest that this productivity is partly controlled by the availability of dissolved iron (dFe). As a first step toward understanding the iron supply of the ASP, we introduce four plausible sources of dFe and simulate their steady spatial distribution using conservative numerical tracers. The modeled distributions replicate important features from observations including dFe maxima at the bottom of deep troughs and enhanced concentrations near the ice shelf fronts. A perturbation experiment with an idealized drawdown mimicking summertime biological uptake and subsequent resupply suggests that glacial meltwater and sediment‐derived dFe are the main contributors to the prebloom dFe inventory in the top 100 m of the ASP. The sediment‐derived dFe depends strongly on the buoyancy‐driven overturning circulation associated with the melting ice shelves (the “meltwater pump”) to add dFe to the upper 300 m of the water column. The results support the view that ice shelf melting plays an important direct and indirect role in the dFe supply and delivery to polynyas such as the ASP.

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Glacial Meltwater Identification in the Amundsen Sea

Cited by 42 publications

References 46 publications

Upper Ocean Distribution of Glacial Meltwater in the Amundsen Sea, Antarctica

Upper Ocean Distribution of Glacial Meltwater in the Amundsen Sea, Antarctica

Vertical Distributions of Macromolecular Composition of Particulate Organic Matter in the Water Column of the Amundsen Sea Polynya During the Summer in 2014

Pathways and supply of dissolved iron in the Amundsen Sea (Antarctica)

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