The Bransfield Gravity Current

Sangrà, Pablo; Stegner, Alexandre; Hernández-Arencibia, Mónica; Marrero-Díaz, Ángeles; Salinas, Carolina; Aguiar‐González, Borja; Henríquez-Pastene, Cristian; Mouriño‐Carballido, Beatriz

doi:10.1016/j.dsr.2016.11.003

Cited by 42 publications

(49 citation statements)

References 41 publications

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“…The main pattern of the ocean circulation in the NAP (Figure 1) is formed by a complex current system governed by (i) the cyclonic gyre and the presence of a surface and a subsurface thermal fronts in the Bransfield Strait (i.e., the Bransfield and Peninsula fronts), (ii) the intrusions of relatively warm, salty and deoxygenated waters derived mainly from the Circumpolar Deep Water (CDW), which flow within the ACC, (iii) the advection of shelf waters by the Antarctic Coastal Current from the NW Weddell Sea continental shelf surrounding the Joinville Island and through the Antarctic Sound, (vi) the southward flow along the west coast of the Antarctic Peninsula toward the Gerlache Strait, and (v) the northward surface waters advection from the Gerlache Strait toward the Bransfield Strait (Smith et al, 1999;Garcia et al, 2002;Von Gyldenfeldt et al, 2002;Zhou et al, 2002Zhou et al, , 2010Heywood et al, 2004;Zhou et al, 2006;Savidge and Amft, 2009;Sangrà et al, 2011;Dotto et al, 2016;Huneke et al, 2016;Sangrà et al, 2017). In addition, a stationary eddy south of Clarence Island and other mesoscales features sourced by displacements of the ACC system and the Bransfield and Peninsula fronts, together with continental input of glacial meltwater, add complexity to the hydrography and ocean mixture along the NAP (Thompson et al, 2009;Azaneu et al, 2017;Moffat and Meredith, 2018).…”

Section: Ocean Circulation In the Napmentioning

confidence: 99%

“…While it is still uncertain how these stressors will shape biological communities along the NAP, several responses have already been observed across multiple trophic levels. At lower levels, repercussions include changes in phytoplankton biomass, composition and size (Montes-Hugo et al, 2009;Mendes et al, 2013;Schofield et al, 2017), as well as declines in Antarctic krill (Euphausia superba) biomass in favor of gelatinous FIGURE 1 | Schematic of the ocean circulation patterns and mesoscale features in the Northern Antarctic Peninsula (NAP), following Smith et al (1999); Garcia et al (2002), Zhou et al (2002); Savidge and Amft (2009), and Sangrà et al (2017). The red arrows depict intrusion of warm waters, whereas the blue arrows depict the cold regime by Weddell Sea shelf waters advection into the NAP.…”

Section: Introductionmentioning

confidence: 99%

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Changes in Phytoplankton Communities Along the Northern Antarctic Peninsula: Causes, Impacts and Research Priorities

et al. 2020

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The Northern Antarctic Peninsula (NAP), located in West Antarctica, is amongst the most impacted regions by recent warming events. Its vulnerability to climate change has already led to an accumulation of severe changes along its ecosystems. This work reviews the current findings on impacts observed in phytoplankton communities occurring in the NAP, with a focus on its causes, consequences, and the potential research priorities toward an integrated comprehension of the physicalbiological coupling and climate perspective. Evident changes in phytoplankton biomass, community composition and size structure, as well as potential bottom-up impacts to the ecosystem are discussed. Surface wind, sea ice and meltwater dynamics, as key drivers of the upper layer structure, are identified as the leading factors shaping phytoplankton. Short-and long-term scenarios are suggested for phytoplankton communities in the NAP, both indicating a future increase of the importance of small flagellates at the expense of diatoms, with potential devastating impacts for the ecosystem. Five main research gaps in the current understanding of the phytoplankton response to climate change in the region are identified: (i) anthropogenic signal has yet to be disentangled from natural climate variability; (ii) the influence of small-scale ocean circulation processes on phytoplankton is poorly understood; (iii) the potential consequences to regional food webs must be clarified; (iv) the magnitude and risk of potential changes in phytoplankton composition is relatively unknown; and (v) a better understanding of phytoplankton physiological responses to changes in the environmental conditions is required. Future research directions, along with specific suggestions on how to follow them, are equally suggested. Overall, while the current

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Section: Ocean Circulation In the Napmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Changes in Phytoplankton Communities Along the Northern Antarctic Peninsula: Causes, Impacts and Research Priorities

et al. 2020

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“…Melting sea ice releases nutrients and leads to enhanced primary production and ocean stratification during spring and summer (Arrigo et al, 1997;Vernet et al, 2008). Interestingly, a higher number of sea ice days is associated with increased photosynthetic efficiency and enhanced carbon fixation rates due to greater nutrient delivery stimulating primary production (Schofield et al, 2018), but thinning of sea ice also affects marine productivity positively (Hancke et al, 2018). Release of dense brine during sea ice formation leads to water mass transformations (Abernathey et al, 2016) that contribute to the thermohaline circulation by feeding deep and intermediate waters (Nicholls et al, 2009) and at the same time inducing upwelling at sea ice edges (Alexander and Niebauer, 1981).…”

Section: Introductionmentioning

confidence: 99%

Sea ice dynamics in the Bransfield Strait, Antarctic Peninsula, during the past 240 years: a multi-proxy intercomparison study

et al. 2020

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Abstract. In the last decades, changing climate conditions have had a severe impact on sea ice at the western Antarctic Peninsula (WAP), an area rapidly transforming under global warming. To study the development of spring sea ice and environmental conditions in the pre-satellite era we investigated three short marine sediment cores for their biomarker inventory with a particular focus on the sea ice proxy IPSO25 and micropaleontological proxies. The core sites are located in the Bransfield Strait in shelf to deep basin areas characterized by a complex oceanographic frontal system, coastal influence and sensitivity to large-scale atmospheric circulation patterns. We analyzed geochemical bulk parameters, biomarkers (highly branched isoprenoids, glycerol dialkyl glycerol tetraethers, sterols), and diatom abundances and diversity over the past 240 years and compared them to observational data, sedimentary and ice core climate archives, and results from numerical models. Based on biomarker results we identified four different environmental units characterized by (A) low sea ice cover and high ocean temperatures, (B) moderate sea ice cover with decreasing ocean temperatures, (C) high but variable sea ice cover during intervals of lower ocean temperatures, and (D) extended sea ice cover coincident with a rapid ocean warming. While IPSO25 concentrations correspond quite well to satellite sea ice observations for the past 40 years, we note discrepancies between the biomarker-based sea ice estimates, the long-term model output for the past 240 years, ice core records, and reconstructed atmospheric circulation patterns such as the El Niño–Southern Oscillation (ENSO) and Southern Annular Mode (SAM). We propose that the sea ice biomarker proxies IPSO25 and PIPSO25 are not linearly related to sea ice cover, and, additionally, each core site reflects specific local environmental conditions. High IPSO25 and PIPSO25 values may not be directly interpreted as referring to high spring sea ice cover because variable sea ice conditions and enhanced nutrient supply may affect the production of both the sea-ice-associated and phytoplankton-derived (open marine, pelagic) biomarker lipids. For future interpretations we recommend carefully considering individual biomarker records to distinguish between cold sea-ice-favoring and warm sea-ice-diminishing environmental conditions.

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“…In the SSI region, observational studies have described the hydrographic structure of the neighbouring Bransfield Strait 24–27 , its circulation 28,29 and the variability of its deep waters 27–30 on a larger spatial scale. Furthermore, a limited number of studies have described the local hydrography of individual fjords during the austral summer 31–33 .…”

Section: Introductionmentioning

confidence: 99%

Oceanographic Variability induced by Tides, the Intraseasonal Cycle and Warm Subsurface Water intrusions in Maxwell Bay, King George Island (West-Antarctica)

Llanillo

Aiken

Cordero

et al. 2019

Sci Rep

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We examine the hydrographic variability induced by tides, winds, and the advance of the austral summer, in Maxwell Bay and tributary fjords, based on two recent oceanographic campaigns. We provide the first description in this area of the intrusion of relatively warm subsurface waters, which have led elsewhere in Antarctica to ice-shelf disintegration and tidewater glacier retreat. During flood tide, meltwater was found to accumulate toward the head of Maxwell Bay, freshening and warming the upper 70 m. Below 70 m, the flood tide enhances the intrusion and mixing of relatively warm modified Upper Circumpolar Deep Water (m-UCDW). Tidal stirring progressively erodes the remnants of Winter Waters found at the bottom of Marian Cove. There is a buoyancy gain through warming and freshening as the summer advances. In Maxwell Bay, the upper 105 m were 0.79 °C warmer and 0.039 PSU fresher in February than in December, changes that cannot be explained by tidal or wind-driven processes. The episodic intrusion of m-UCDW into Maxwell Bay leads to interleaving and eventually to warming, salinification and deoxygenation between 80 and 200 m, with important implications for biological productivity and for the mass balance of tidewater glaciers in the area.

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The Bransfield Gravity Current

Cited by 42 publications

References 41 publications

Changes in Phytoplankton Communities Along the Northern Antarctic Peninsula: Causes, Impacts and Research Priorities

Changes in Phytoplankton Communities Along the Northern Antarctic Peninsula: Causes, Impacts and Research Priorities

Sea ice dynamics in the Bransfield Strait, Antarctic Peninsula, during the past 240 years: a multi-proxy intercomparison study

Oceanographic Variability induced by Tides, the Intraseasonal Cycle and Warm Subsurface Water intrusions in Maxwell Bay, King George Island (West-Antarctica)

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