A deep cyclonic gyre in the Australian–Antarctic Basin

McCartney, Michael S.; Donohue, Kathleen

doi:10.1016/j.pocean.2007.02.008

Cited by 112 publications

(138 citation statements)

References 125 publications

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“…It is currently suggested that 60% of the total AABW is formed in the Weddell Sea and the rest is formed in the Ross Sea and Adélie and George V Land region 4 . The AABW from the Adélie and George V Land region, in conjunction with AABW from the Ross Sea, ultimately supplies to the abyssal layers of the eastern Indian and Pacific oceans 4,14,27 , influences the variability of their abyssal layers. We estimate that the 0.36×10 6 m 3 s − 1 reduction in AABW from the Adélie and George V Land region found in this study leads to about 6-9% reduction in the AABW of these ocean basins.…”

Section: Discussionmentioning

confidence: 99%

Impact of the Mertz Glacier Tongue calving on dense water formation and export

2011

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Antarctic Bottom Water (AABW) is a critical component of the global climate system, occupying the abyssal layer of the World Ocean and driving the lower limb of the global meridional overturning circulation. Around East Antarctica, the dense shelf water (DSW) precursor to AABW is predominantly formed by enhanced sea ice formation in coastal polynyas. The dominant source region of AABW supply to the Australian-Antarctic Basin is the Adélie and George V Land coast, in particular, polynyas formed in the western lee of the Mertz Glacier Tongue (MGT) and the grounded iceberg B9b over the Adélie and the Mertz Depressions, respectively. The calving of the MGT, which occurred on 12-13 February 2010, dramatically changed the environment for producing DSW. Here, we assess its impact using a state-of-the-art ice-ocean model. The model shows that oceanic circulation and sea ice production in the region changes immediately after the calving event, and that the DSW export is reduced by up to 23%.

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Section: Discussionmentioning

confidence: 99%

Impact of the Mertz Glacier Tongue calving on dense water formation and export

2011

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“…Inspection of the barotropic streamfunction (BSF) (Danabasoglu et al 2012, their Fig. 13) suggests that this is part of a cyclonic gyre in the AAB (McCartney and Donohue 2007). Below a surface-intensified flow in the upper 500 m, the vertical structure is barotropic and lacks the bottom intensification apparent in observations (Fukamachi et al 2010).…”

Section: B Export Of Aabwmentioning

confidence: 97%

The Southern Ocean and Its Climate in CCSM4

et al. 2012

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The new Community Climate System Model, version 4 (CCSM4), provides a powerful tool to understand and predict the earth's climate system. Several aspects of the Southern Ocean in the CCSM4 are explored, including the surface climatology and interannual variability, simulation of key climate water masses (Antarctic Bottom Water, Subantarctic Mode Water, and Antarctic Intermediate Water), the transport and structure of the Antarctic Circumpolar Current, and interbasin exchange via the Agulhas and Tasman leakages and at the Brazil-Malvinas Confluence. It is found that the CCSM4 has varying degrees of accuracy in the simulation of the climate of the Southern Ocean when compared with observations. This study has identified aspects of the model that warrant further analysis that will result in a more comprehensive understanding of oceanatmosphere-ice dynamics and interactions that control the earth's climate and its variability.

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“…The Kerguelen Plateau is a large igneous province (LIP) in the Indian sector of the Southern Ocean that acts as a barrier to the circumpolar flow of the ACC, forcing 2/3 of the flow to pass along the northern escarpment of the plateau, which lies to the north of Kerguelen Island, and the remaining third to flow through the Fawn Trough, which lies to the south of Heard Island (Park et al, 1993;Mongin et al, 2008;Roquet et al, 2009). Thus, despite being in the midst of the ACC, the relatively shallow region between Kerguelen Island and Heard Island represents a zone of weak eastward circulation (Park et al, 1998b;McCartney and Donohue, 2007;Roquet et al, 2009), with the potential for a high degree of nutrient recycling (due to its retention of water and particulates) and of input of material from the subaerial and submarine weathering of basalt. These factors, along with natural iron fertilization on the plateau (Blain et al, 2007), allow considerable biological nutrient removal and buildup of standing stocks of chlorophyll and BSi to occur in this area during phytoplankton blooms relative to the surrounding open ocean waters of the ACC (De La Rocha et al, 2011;Fripiat et al, 2011b).…”

Section: Introductionmentioning

confidence: 99%

Exploring interacting influences on the silicon isotopic composition of the surface ocean: a case study from the Kerguelen Plateau

2014

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Abstract. This study presents six new water column profiles of the silicon isotopic composition (δ 30 Si) of dissolved silicon (DSi) from the Atlantic and Indian sectors of the Southern Ocean and a variable depth box model of silica cycling in the mixed layer that was constructed to illuminate the evolution of surface ocean δ 30 Si over the full course of a year. In keeping with previous observations, δ 30 Si values ranged from +1.9 to +2.4 ‰ in the mixed layer (ML), +1.2 to +1.7 ‰ in Winter Water (WW), and +0.9 to +1.4 ‰ in Circumpolar Deep Water (CDW). These data also confirmed the occurrence of diminished values for ML δ 30 Si at low DSi concentrations in early austral autumn on the Kerguelen Plateau. The box model was used to investigate whether these low, post-growing season values of δ 30 Si were related to input of DSi to the ML from basalt weathering, biogenic silica dissolution (with or without isotopic fractionation), the onset of winter mixing, or some combination of the three. Basalt weathering and fractionation during biogenic silica dissolution could both lower ML δ 30 Si below what would be expected from the extent of biological uptake of DSi. However, the key driver of the early autumn decrease in δ 30 Si appears to be the switch from bloom growth (with net removal of DSi and net accumulation of biogenic silica (BSi) biomass) to steady state growth (when slow but continuing production of BSi prevented significant net increase in DSi concentrations with diffusive input of DSi from WW but not decrease in ML δ 30 Si towards WW values). Model results also indicated that fractionation during dissolution has only a negligible effect on the δ 30 Si of BSi exported throughout the course of the year. However, seasonal changes in export efficiency (e.g. favouring the export of bloom BSi versus the export of BSi produced during other times of the year) should strongly influence the δ 30 Si of BSi accumulating in marine sediments.Finally, the choice for the parameterisation of the mixing between the ML and the WW in terms of δ 30 Si (i.e. constant or allowed to vary with the seasonal migration of the thermocline) is critical to take into account in box model simulations of the silica biogeochemical cycle. Altogether, these results suggest that as a paleoceanographic proxy, δ 30 Si may more reflect the dominant mode of production of the BSi that is exported (i.e. bloom versus steady state growth) rather than strictly the extent of DSi utilisation by diatoms.

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A deep cyclonic gyre in the Australian–Antarctic Basin

Cited by 112 publications

References 125 publications

Impact of the Mertz Glacier Tongue calving on dense water formation and export

Impact of the Mertz Glacier Tongue calving on dense water formation and export

The Southern Ocean and Its Climate in CCSM4

Exploring interacting influences on the silicon isotopic composition of the surface ocean: a case study from the Kerguelen Plateau

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