The Deep‐Water Plume in the Northwestern Weddell Sea, Antarctica: Mean State, Seasonal Cycle and Interannual Variability Influenced by Climate Modes

Llanillo, P. J.; Kanzow, Torsten; Janout, Markus; Rohardt, Gerd

doi:10.1029/2022jc019375

Cited by 4 publications

(5 citation statements)

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“…Variability of the dense water plume (velocity and location) flowing along the continental slope is associated with a wide range of timescale. Interannual variability is associated with climate modes (Southern Annular Mode; El Nino Southern Oscillation), and it superimposes on lower frequency change, as observed from a set of mooring at the tip of the Antarctic Peninsula [ 58 ]. Low-frequency change also shows up in historical repeated observations.…”

Section: Advances In Our Understanding Of Southern Ocean Carbon and H...mentioning

confidence: 99%

“…regional warming in East Asia via atmospheric teleconnections [ 66 ]. Atmospheric patterns and climate modes can in turn have important implications for the melt of Antarctic ice shelves [ 67 ], for the thermohaline properties of the dense water plumes both at source regions [ 54 ], during their export downslope [ 58 ], and in consequence for bottom water properties [ 59 ]. The use of an unprecedented set of observations from hot-water drilled boreholes in the Filchner–Ronne ice shelf allowed to show the importance of the Amundsen Sea Low position in setting the cavity circulation and its melt rate.…”

Section: Advances In Our Understanding Of Southern Ocean Carbon and H...mentioning

confidence: 99%

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Southern ocean carbon and heat impact on climate

Sallée

Abrahamsen

Allaigre

et al. 2023

Phil. Trans. R. Soc. A.

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The Southern Ocean greatly contributes to the regulation of the global climate by controlling important heat and carbon exchanges between the atmosphere and the ocean. Rates of climate change on decadal timescales are therefore impacted by oceanic processes taking place in the Southern Ocean, yet too little is known about these processes. Limitations come both from the lack of observations in this extreme environment and its inherent sensitivity to intermittent processes at scales that are not well captured in current Earth system models. The Southern Ocean Carbon and Heat Impact on Climate programme was launched to address this knowledge gap, with the overall objective to understand and quantify variability of heat and carbon budgets in the Southern Ocean through an investigation of the key physical processes controlling exchanges between the atmosphere, ocean and sea ice using a combination of observational and modelling approaches. Here, we provide a brief overview of the programme, as well as a summary of some of the scientific progress achieved during its first half. Advances range from new evidence of the importance of specific processes in Southern Ocean ventilation rate (e.g. storm-induced turbulence, sea–ice meltwater fronts, wind-induced gyre circulation, dense shelf water formation and abyssal mixing) to refined descriptions of the physical changes currently ongoing in the Southern Ocean and of their link with global climate. This article is part of a discussion meeting issue ‘Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities’.

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Section: Advances In Our Understanding Of Southern Ocean Carbon and H...mentioning

confidence: 99%

Section: Advances In Our Understanding Of Southern Ocean Carbon and H...mentioning

confidence: 99%

Southern ocean carbon and heat impact on climate

Sallée

Abrahamsen

Allaigre

et al. 2023

Phil. Trans. R. Soc. A.

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“…AABW originated from the south-western Weddell Sea is also monitored as part of a German observational effort. Since 1989, the Alfred Wegener Institute maintains a mooring array located in a cross-slope transect off the tip of the Antarctic Peninsula (NW moorings; see Figure 5D) that allows to study the time evolution of the dense plumes flowing along the continental slope in the northwestern Weddell Sea (Fahrbach et al, 2001;Llanillo et al, 2023). Further downstream, the US Lamont-Doherty Earth Observatory maintains moorings south of the South Orkney Islands (Figure 5D) that record two decades (since 1999) of AABW temperature and salinity properties exported from the western boundary of the Weddell Sea.…”

Section: Weddell Seamentioning

confidence: 99%

“…Locations of all moorings are shown in Figure 5 by red stars. associated with the Southern Annular Mode (SAM) and El Niño/ Southern Oscillation (ENSO) (McKee et al, 2011;Gordon et al, 2020;Llanillo et al, 2023;Zhou et al, 2023). AABW export detected since February 1999 reveals a distinct seasonal cycle as well as interannual variability (Figure 7B).…”

Section: Weddell Seamentioning

confidence: 99%

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Observing Antarctic Bottom Water in the Southern Ocean

Silvano,

Purkey,

Gordon

et al. 2023

Front. Mar. Sci.

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Dense, cold waters formed on Antarctic continental shelves descend along the Antarctic continental margin, where they mix with other Southern Ocean waters to form Antarctic Bottom Water (AABW). AABW then spreads into the deepest parts of all major ocean basins, isolating heat and carbon from the atmosphere for centuries. Despite AABW’s key role in regulating Earth’s climate on long time scales and in recording Southern Ocean conditions, AABW remains poorly observed. This lack of observational data is mostly due to two factors. First, AABW originates on the Antarctic continental shelf and slope where in situ measurements are limited and ocean observations by satellites are hampered by persistent sea ice cover and long periods of darkness in winter. Second, north of the Antarctic continental slope, AABW is found below approximately 2 km depth, where in situ observations are also scarce and satellites cannot provide direct measurements. Here, we review progress made during the past decades in observing AABW. We describe 1) long-term monitoring obtained by moorings, by ship-based surveys, and beneath ice shelves through bore holes; 2) the recent development of autonomous observing tools in coastal Antarctic and deep ocean systems; and 3) alternative approaches including data assimilation models and satellite-derived proxies. The variety of approaches is beginning to transform our understanding of AABW, including its formation processes, temporal variability, and contribution to the lower limb of the global ocean meridional overturning circulation. In particular, these observations highlight the key role played by winds, sea ice, and the Antarctic Ice Sheet in AABW-related processes. We conclude by discussing future avenues for observing and understanding AABW, impressing the need for a sustained and coordinated observing system.

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Wind Forcing Controls on Antarctic Bottom Water Export From the Weddell Sea via Bottom Boundary Layer Processes

Auckland,

Abrahamsen,

Meredith

et al. 2024

JGR Oceans

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The Antarctic Bottom Water (AABW) exported from the Weddell Sea has experienced warming and contraction in the past 30 yrs. Superposed on this decadal trend is substantial annual and interannual variability in the volume and properties of Weddell‐sourced AABW. Several mechanisms have been suggested to explain these variations, many of which highlight a role of wind stress, but the comparative importance and possible simultaneity of the different mechanisms remains unclear. Using data from two mooring sites within the Weddell Sea, we find a rapid intensification of the abyssal boundary current carrying AABW through Orkney Passage (OP), the most direct export pathway of AABW from the Weddell Sea, in response to periods of strong zonal wind stress and anomalous wind stress curl along the South Scotia Ridge upstream of OP. This acceleration is concomitant with a 40% reduction in northward AABW transport in late 2015. The changes in transport follow anomalous wind forcing by approximately 3 months, with the short timescale indicative of a barotropic response in the flow through OP. The bottom boundary layer over the OP's sloping topography is found to have a key role in regulating export on monthly to interannual timescales. Increased boundary current velocity leading up to the passage forms a thickened bottom boundary layer, resulting in reduced AABW thickness and density, and thus restricting northward transport of AABW through the passage. Whilst other processes are likely to dominate on longer (decadal) periods, the dynamics identified here can explain significant variability on timescales up to interannual.

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The Deep‐Water Plume in the Northwestern Weddell Sea, Antarctica: Mean State, Seasonal Cycle and Interannual Variability Influenced by Climate Modes

Cited by 4 publications

References 85 publications

Southern ocean carbon and heat impact on climate

Southern ocean carbon and heat impact on climate

Observing Antarctic Bottom Water in the Southern Ocean

Wind Forcing Controls on Antarctic Bottom Water Export From the Weddell Sea via Bottom Boundary Layer Processes

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