Strong ice-ocean interaction beneath Shirase Glacier Tongue in East Antarctica

Hirano, Daisuke; Tamura, Takeshi; Kusahara, Kazuya; Ohshima, Κay I.; Nicholls, Keith W.; Ushio, Shuki; Simizu, Daisuke; Ono, Kentaro; Fujii, Mahito; Nogi, Yoshifumi; Aoki, Shigeru

doi:10.1038/s41467-020-17527-4

Cited by 44 publications

(59 citation statements)

References 68 publications

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“…Colored circles in Fig. 7 are subsampled ocean properties from the in-situ observations (Hirano et al, 2020). The two-layer feature in the model is consistent with the observation results.…”

Section: Intrusion Of Modified Circumpolar Deep Water Into Lhbsupporting

confidence: 82%

“…On the western side of the trough, northward flow of cold and fresh water is reproduced at the surface and intermediate depths. The overturning circulation in the model is generally consistent with that inferred from the observed water properties (temperature, salinity, oxygen, and the stable oxygen isotope ratio, δ 18 O, Hirano et al, 2020).…”

Section: Intrusion Of Modified Circumpolar Deep Water Into Lhbsupporting

confidence: 74%

“…This seasonal cycle of the density surfaces in the box area is explained by 305 the seasonality of the alongshore wind (Fig. 3, Hirano et al, (2020), and Ohshima et al (1996)). Note that the seasonal cycle in the FI case is more apparent than that in the NOFI case because the fast ice cover plays a role as a physical barrier for the surface momentum flux and the wind stress curl input caused by the combination of fast ice edge and the alongshore easterly wind result in pronounced Ekman downwelling in this region (Ohshima, 2000).…”

Section: Warm Water Intrusions From the Continental Shelf Break And Smentioning

confidence: 90%

“…11; box area indicated in 390 Fig. 6), although there is a similar seasonal cycle in the deep layer (σ0 > 27.5 kg m -3 ) in the NOFI and FI cases via the winddriven Ekman dynamics (Hirano et al, 2020;Ohshima et al, 1996), the seasonal cycle of the water properties in the surface layers is different. The surface stratification in the FI case is stronger than that in the NOFI case due to a combination of the surplus freshwater fluxes and the less-modification of the surface water by the negligible sea ice formation in the FI case.…”

mentioning

confidence: 92%

“…The bottom topography in the LHB bay region (35-40°E, and 70-68°S) was replaced with a detailed topography that blended multi-beam surveys from the 51st-55th JARE expeditions, point echo sounding using sea ice drill holes from the 9th-22nd JARE expeditions (Moriwaki and Yoshida, 1983), depth data from the nautical chart created by Japan Coast Guard (JCG), in which ship-based single-beam echo sounding data obtained in several JARE expeditions were included, and ETOPO1 (Amante and 130 Eakins, 2009). The detail for the compiled bottom topography was described in the Method section in Hirano et al (2020). In a later subsection 2.3, we compare the newly-compiled bottom topography with several topography datasets.…”

mentioning

confidence: 99%

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Modeling intensive ocean–cryosphere interactions in Lützow-Holm Bay, East Antarctica

Kusahara¹,

Hirano²,

Fujii³

et al. 2020

Preprint

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Abstract. Basal melting of Antarctic ice shelves accounts for more than half of the mass loss from the Antarctic Ice Sheet. Many studies have focused on active basal melting at ice shelves in the Amundsen-Bellingshausen Seas and the Totten Ice shelf, East Antarctica. In these regions, the intrusion of Circumpolar Deep Water (CDW) onto the continental shelf is a key component for the localized intensive basal melting. Both regions have a common oceanographic feature: southward deflection of the Antarctic Circumpolar Current on the eastern flank of ocean gyres brings CDW onto the continental shelves. The physical setting of Shirase Glacier Tongue (SGT) in Lützow-Holm Bay corresponds to a similar configuration for the Weddell Gyre in the Atlantic sector. Here, we conduct a 2–3 km resolution simulation of an ocean-sea ice-ice shelf model using a newly-compiled bottom topography dataset in the bay. The model can reproduce the observed CDW intrusion along the deep trough. The modeled SGT basal melting reaches a peak in summer and minimum in autumn and winter, consistent with the wind-driven seasonality of the CDW thickness in the bay. The model results suggest the existence of eastward-flowing undercurrent on the upper continental slope in summer, and the undercurrent contributes to the seasonal-to-interannual variability of the warm water intrusion into the bay. Furthermore, numerical experiments with and without fast-ice cover in the bay demonstrate that fast ice plays a role as an effective thermal insulator and reduces local sea-ice formation, resulting in much warmer water intrusion into the SGT cavity.

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Section: Intrusion Of Modified Circumpolar Deep Water Into Lhbsupporting

confidence: 82%

Section: Intrusion Of Modified Circumpolar Deep Water Into Lhbsupporting

confidence: 74%

Section: Warm Water Intrusions From the Continental Shelf Break And Smentioning

confidence: 90%

mentioning

confidence: 92%

mentioning

confidence: 99%

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Modeling intensive ocean–cryosphere interactions in Lützow-Holm Bay, East Antarctica

Kusahara¹,

Hirano²,

Fujii³

et al. 2020

Preprint

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Impacts of basal melting of the Totten Ice Shelf and biological productivity on marine biogeochemical components in Sabrina Coast, East Antarctica

Tamura

Nomura

Hirano

et al. 2022

Preprint

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To clarify the impact of basal melting of the Antarctic ice sheet and biological productivity on biogeochemical processes in Antarctic coastal waters, concentrations of dissolved inorganic carbon (DIC), total alkalinity (TA), inorganic nutrients, chlorophyll a, and stable oxygen isotopic ratios (δ 18 O) were measured from the offshore slope to the ice front of the Totten Ice Shelf (TIS) during the spring/summer of 2018, 2019, and 2020. Off the TIS, modified Circumpolar Deep Water (mCDW) intruded onto the continental shelf and flowed along bathymetric troughs into the TIS cavity, where it met the ice shelf base and formed a buoyant mixture with glacial meltwater. Physical oceanographic processes mostly determined the distributions of DIC, TA, and nutrient concentrations. However, DIC, TA, and nutrient concentrations on the surface of the ice front were decreased by photosynthesis and the dilution effect of meltwater from sea ice and the base of the ice shelf. The partial pressure of CO 2 (pCO 2 ) in surface water was reduced by photosynthesis and dilution, and the surface water became a strong CO 2 sink for the atmosphere. The DIC and TA (normalized to salinity of 34.3 to correct for dilution effects) changed in a molar ratio of 106:16 because of phytoplankton photosynthesis. The decrease of pCO 2 by more than 100 μatm with respect to mCDW was thus the result of photosynthesis. The nutrient consumption ratio suggested that enough iron was present in the water column to supply the surface layer via buoyancy-driven upwelling and basal melting of the TIS. Hosted filetable1.docx available at https://authorea.com/users/534203/articles/598413-impacts-of-basalmelting-of-the-totten-ice-shelf-and-biological-productivity-on-marine-biogeochemicalcomponents-in-sabrina-coast-east-antarctica Hosted file support infomation tamura p et al.docx

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Shoreward intrusion of oceanic surface waters alters physical and biological ocean structures on the Antarctic continental shelf during winter: Observations from instrumented seals

Kokubun

Tanabe

Hirano

et al. 2021

Limnology & Oceanography

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Ocean circulation plays a key role in structuring marine ecosystems in the Southern Ocean. However, the seasonal dynamics of ocean circulation are poorly understood in the ice‐covered continental shelves due to difficulties in conducting observations. We, therefore, investigated spatial and temporal variations in oceanographic conditions and their biological effects on the continental shelf off East Antarctica (35°E–50°E) by deploying conductivity–temperature–depth (CTD) tags on Weddell seals. The seals moved up to 633 km east from the tagging location. We successfully obtained 1254 CTD casts from seven seals. Winter Water (WW) was most prevalent (77.4% of the total data), followed by Supercooled Water (14.2%), Antarctic Surface Water (AASW: 7.4%), Modified Circumpolar Deep Water (mCDW; 0.9%), and Modified Shelf Water (0.1%). During our study period, landfast ice broke up extensively, and the easterly wind was most prevalent during autumn. AASW was observed in the subsurface layer over the shelf in autumn, suggesting that AASW intruded from the surface of off‐shelf areas through Ekman transport. Particular water masses (mCDW, AASW, and WW below the AASW) had positive effects on the seals' foraging behavior. These results highlight the importance of easterly wind‐driven shoreward intrusion of oceanic surface waters onto the shelf in autumn. This physical process may enhance transport and accumulation of additional prey and increase local prey availability during winter. Such a process may play important roles in the Antarctic coastal marine ecosystems that are influenced by landfast ice.

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Strong ice-ocean interaction beneath Shirase Glacier Tongue in East Antarctica

Cited by 44 publications

References 68 publications

Modeling intensive ocean–cryosphere interactions in Lützow-Holm Bay, East Antarctica

Modeling intensive ocean–cryosphere interactions in Lützow-Holm Bay, East Antarctica

Impacts of basal melting of the Totten Ice Shelf and biological productivity on marine biogeochemical components in Sabrina Coast, East Antarctica

Shoreward intrusion of oceanic surface waters alters physical and biological ocean structures on the Antarctic continental shelf during winter: Observations from instrumented seals

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