Winter water variability in the Indian Ocean sector of Southern Ocean during austral summer

Sabu, P.; Libera, Stephy Ann; Chacko, Racheal; Anilkumar, N.; Subeesh, M.P.; Thomas, Antony P.

doi:10.1016/j.dsr2.2020.104852

Cited by 8 publications

(8 citation statements)

References 32 publications

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“…Between the seasonal sea ice zone and the Polar Front, the mixed layer temperature is warmer, ranging from −1.5°C to 1.5°C (Pellichero et al., 2017). During spring and summer, enhanced solar insolation and ice melt creates a relatively warm and fresh surface layer that caps the winter mixed layer, leaving a cold sub‐surface remnant known as WW (Moffat & Meredith, 2018; Sabu et al., 2020). The summertime vertical temperature profile is therefore characterized by warm‐cold‐warm layering, with the WW layer typically occupying the depth range from 50 to 200 m (Figure ).…”

Section: Methods Rationalementioning

confidence: 99%

“…Between the seasonal sea ice zone and the Polar Front, the mixed layer temperature is warmer, ranging from -1.5ºC to 1.5ºC (Pellichero et al, 2017). During spring and summer, enhanced solar insolation and ice melt creates a relatively warm and fresh surface layer that caps the winter mixed layer, leaving a cold subsurface remnant known as winter water (WW) (Moffat & Meredith, 2018;Sabu et al, 2020).…”

Section: Accepted Articlementioning

confidence: 99%

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Tracking Southern Ocean Sea Ice Extent With Winter Water: A New Method Based on the Oxygen Isotopic Signature of Foraminifera

Lund

Chase

Kohfeld

et al. 2021

Paleoceanog and Paleoclimatol

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Southern Ocean sea ice plays a central role in the oceanic meridional overturning circulation, transforming globally prevalent watermasses through surface buoyancy loss and gain. Buoyancy loss due to surface cooling and sea ice growth promotes the formation of bottom water that flows into the Atlantic, Indian, and Pacific basins, while buoyancy gain due to sea ice melt helps transform the returning deep flow into intermediate and mode waters. Because northward expansion of Southern Ocean sea ice during the Last Glacial Maximum (LGM; 19–23 kyr BP) may have enhanced deep ocean stratification and contributed to lower atmospheric CO2 levels, reconstructions of sea ice extent are critical to understanding the LGM climate state. Here, we present a new sea ice proxy based on the 18O/16O ratio of foraminifera (δ18Oc). In the seasonal sea ice zone, sea ice formation during austral winter creates a cold surface mixed layer that persists in the sub‐surface during spring and summer. The cold sub‐surface layer, known as winter water, sits above relatively warm deep water, creating an inverted temperature profile. The unique surface‐to‐deep temperature contrast is reflected in estimates of equilibrium δ18Oc, implying that paired analysis of planktonic and benthic foraminifera can be used to infer sea ice extent. To demonstrate the feasibility of the δ18Oc method, we present a compilation of N. pachyderma and Cibicidoides spp. results from the Atlantic sector that yields an estimate of winter sea ice extent consistent with modern observations.

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Section: Methods Rationalementioning

confidence: 99%

Section: Accepted Articlementioning

confidence: 99%

Tracking Southern Ocean Sea Ice Extent With Winter Water: A New Method Based on the Oxygen Isotopic Signature of Foraminifera

Lund

Chase

Kohfeld

et al. 2021

Paleoceanog and Paleoclimatol

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“…Lund et al (2021) show similar spatial variability across the circumpolar SO via climatological WW temperatures. Sabu et al (2020) also observe the WW layer responding to largescale atmospheric variability, finding enhanced warming in years of positive Southern Annular Mode, likely due to elevated wind-driven mixing from stronger winds. The variability of WW observed is tied to various mechanisms that impact upper ocean structure, such as varying eddy kinetic energy (Dove et al, 2022;Nikurashin et al, 2013), differing wind stress fields (Abernathey et al, 2011;Lin et al, 2018), and CDW outcropping pathways (Narayanan et al, 2023;Tamsitt et al, 2021).…”

Section: Introductionmentioning

confidence: 72%

“…However, these findings are specific to the Weddell Sea where there is typically a sharp thermocline yet a weak pycnocline (Wilson et al, 2019), which impacts the temperature gradient as well as the rate of mixing that takes place. Further, variability of WW properties have been observed in regions up-and downstream of large topographic features that interact with the ACC, enhancing the downstream mesoscale field, such as that found by Sabu et al (2020). Lund et al (2021) show similar spatial variability across the circumpolar SO via climatological WW temperatures.…”

Section: Introductionmentioning

confidence: 90%

The observed spatiotemporal variability of Antarctic Winter Water

Spira,

Swart,

Giddy

et al. 2024

Preprint

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The Southern Ocean is central to the global overturning circulation. South of the Antarctic Polar Front, Antarctic Winter Water (WW) forms in the wintertime mixed layer below sea ice and becomes a subsurface layer following summertime restratification of the mixed layer, overlaying upwelled deep waters. Model simulations show that WW acts as a conduit to seasonally transform upwelled deep waters into intermediate waters. Yet, there remains little observational evidence of the distribution and seasonal characteristics of WW. Using 18 years of in situ observations, we show seasonal climatologies of WW thickness, depth, core temperature and salinity. This study reveals, for the first time, the distinct regionality and seasonality of WW. The seasonal cycle of WW characteristics is tied to the annual sea ice evolution, whilst the spatial distribution is impacted by the main topographic features in the Southern Ocean driving an equatorward flux of WW. Through the identification of these localized northward export regions of WW, this study provides further evidence suggesting an alternative view from the conventional ‘zonal mean’ perspective of the overturning circulation. We show that specific overturning pathways connecting the subpolar ocean to the global ocean can be explained by ocean-topography interactions.

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“…Within the South Indian Ocean the opposite trend in sea ice extent occurs during positive SAM, where, unlike the Southwest Pacific Ocean sector showing sea ice decreases during positive SAM and La Niña events (Bengtson Nash et al, 2018), there is greater sea ice extent during positive SAM (as well as La Niña periods) (Kohyama and Hartmann, 2016). This was also shown through intense negative SST anomalies associated with positive SAM in the Indian Ocean, while negative SAM events were associated with positive SST anomalies (Sabu et al, 2020). Therefore, if the isotopic variability reflects changes in feeding success, it may be possible whales within the South Indian Ocean experience better feeding opportunities (i.e., better krill recruitment) during these times as seen through an increase in low nitrogen and carbon stable isotope values.…”

Section: Humpbacks Of the D Breeding Stock And The Southern Right Wha...mentioning

confidence: 95%

Whales and climate

2024

Frontiers Research Topics

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Frontiers is more than just an open access publisher of scholarly articles: it is a pioneering approach to the world of academia, radically improving the way scholarly research is managed. The grand vision of Frontiers is a world where all people have an equal opportunity to seek, share and generate knowledge. Frontiers provides immediate and permanent online open access to all its publications, but this alone is not enough to realize our grand goals. Frontiers journal seriesThe Frontiers journal series is a multi-tier and interdisciplinary set of openaccess, online journals, promising a paradigm shift from the current review, selection and dissemination processes in academic publishing. All Frontiers journals are driven by researchers for researchers; therefore, they constitute a service to the scholarly community. At the same time, the Frontiers journal series operates on a revolutionary invention, the tiered publishing system, initially addressing specific communities of scholars, and gradually climbing up to broader public understanding, thus serving the interests of the lay society, too. Dedication to qualityEach Frontiers article is a landmark of the highest quality, thanks to genuinely collaborative interactions between authors and review editors, who include some of the world's best academicians. Research must be certified by peers before entering a stream of knowledge that may eventually reach the public -and shape society; therefore, Frontiers only applies the most rigorous and unbiased reviews. Frontiers revolutionizes research publishing by freely delivering the most outstanding research, evaluated with no bias from both the academic and social point of view. By applying the most advanced information technologies, Frontiers is catapulting scholarly publishing into a new generation. What are Frontiers Research Topics?Frontiers Research Topics are very popular trademarks of the Frontiers journals series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area.

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Winter water variability in the Indian Ocean sector of Southern Ocean during austral summer

Cited by 8 publications

References 32 publications

Tracking Southern Ocean Sea Ice Extent With Winter Water: A New Method Based on the Oxygen Isotopic Signature of Foraminifera

Tracking Southern Ocean Sea Ice Extent With Winter Water: A New Method Based on the Oxygen Isotopic Signature of Foraminifera

The observed spatiotemporal variability of Antarctic Winter Water

Whales and climate

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