A note on the thermal structure of the upper ocean in the Bransfield Strait-South Shetland Islands region

Capella, Jorge E.; Ross, Robin M.; Quetin, Langdon B.; Hofmann, Eileen E.

doi:10.1016/0198-0149(92)90065-2

Cited by 45 publications

(20 citation statements)

References 3 publications

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“…This is consistent with summertime observations from the Palmer Long Term Ecological Research (LTER) program, which show minimal amounts of mixing between Bransfield Strait waters and the waters farther south (Capella et al, 1992;Smith et al, 1999).…”

Section: Evidence For the Apcc Upstream Of Section Isupporting

confidence: 74%

Ocean circulation and dynamics on the west Antarctic Peninsula continental shelf

Moffat¹

2007

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Observations of current velocity, temperature, salinity and pressure from a 2-year moored array deployment and four hydrographic cruises conducted by the United States Southern Ocean GLOBEC program on the western Antarctic Peninsula continental shelf are used to characterize the ocean circulation and its connection to fresh water and heat fluxes on the shelf. Mean velocities on the shelf are of the order of 5 cm/s or less. Tidal motions are dominated by the M 2 and S 2 semi-diurnal tides and the O 1 and K 1 diurnal tides, although the tidal velocities are typically less than 2 cm/s. Near-inertial motions are relatively large, with current velocities as high as 26 cm/s. It is shown that Marguerite Trough, a large bathymetric feature connecting the shelf-break to Marguerite Bay, plays a critical role in determining the circulation. The mean flow is strongly steered in the along-slope direction, and the tidal currents also show increasing current polarization at depth in Marguerite Trough. At timescales of 5 to 20 days, the observations show bottom-intensified motion in Marguerite Trough consistent with bottom-trapped topographic Rossby waves. The subtidal circulation in the trough has a significant wind-driven component in Marguerite Trough, with downwelling-favorable winds forcing cross-shelf flow on the northern side of the trough and along the shore on the outer shelf. Upwelling-favorable winds force roughly the opposite circulation. The cyclonic circulation on the trough helps advect blobs of salty, warm and nutrient-rich water across the shelf. These intrusions are small (≈4 km) and frequent (4 events/month). Also, the Antarctic Peninsula Coastal Current (APCC), a coastal buoyant current which is described for the first time here. The APCC is a seasonal current which is only present during the ice-free season and is forced by freshwater fluxes associated with large glacier melt and precipitation rates in the region. This section would be in danger of becoming a Chapter were I to list all of the good friends I've met here. But! Special mention to the PO crowd:

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Section: Evidence For the Apcc Upstream Of Section Isupporting

confidence: 74%

Ocean circulation and dynamics on the west Antarctic Peninsula continental shelf

Moffat¹

2007

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“…Both the Drake Passage and Bransfield Strait sides of the South Shedand Islands have strong, alongshore currents that move in a northeasterly direction [Capella, 1992]. However, the predominant wind direction in this region is westerly, with winds strong and persistent, especially in the spring and fall [Smith et al, this volume].…”

Section: Distribution Of Addlie Colonies In the Scotia Arcmentioning

confidence: 98%

The breeding biology and distribution of Adélie penguins: Adaptations to environmental variability

Trivelpiece¹,

Fraser²

1996

Foundations for Ecological Research West of the Antarctic Peninsula

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Ad6lie penguins are long-lived, highly philopatric seabirds that dominate the bird biomass of the Western Antarctic Peninsula region, and serve as focal animals for our Long-Term Ecological Research (LTER) study of the effects of environmental variability on animal populations in the Antarctic marine ecosystem. The major physical factors affecting the breeding success, distribution and demography of Ad61ie penguins in the Southern Ocean are variability in sea ice cover, ocean circulation patterns and terrestrial topography. We analyzed Ad61ie distributions in the Antarctic Peninsula region and concluded that Ad61ie penguins have discrete subpopulations in the northeastern and southwestern regions of the area. These subpopulations are separated by a 400 km gap in their respective dislributions, but each is within several hundred kilometers of predictable pack ice areas in the Weddell and Bellingshausen Seas, respectively. We propose that these pack ice areas are the wintering grounds for each subpopulation, and that access to these pack ice areas, early in the season following courtship fasting, is the key to successful breeding in Ad61ies. We further analyzed the colony distributions within each subpopulation and found highly clumped distributions of Ad61ie penguins that were strongly correlated to physical factors such as bathymetry, currents and wind direction. We propose that these variables reduce the occurrence of pack ice in the vicinity of breeding colonies of Ad61ie penguin populations, thereby assuring access to open water in the early season. Finally, we examined the influence of the interaction of local topography and weather on the size, location and persistence of breeding groups within Ad61ie penguin colonies. Snow accumulation, melt water runoff and solar radiation all impact the microclimate of breeding colonies and influence the selection of nesting sites among Ad61ie penguins. The abandonment of breeding areas by Ad6lie penguins, following two to three years of failure at "poor" sites, suggests that changes in the population distribution of Ad61ie penguins may be very rapid in response to changing environmental conditions, such as increased snow deposition. Adaptations to environmental variability are seen in every aspect of the natural history of the Ad61ie penguin, from the distribution of subpopulations around Antarctica, to the sizes and distributions of colonies within regions, to the choice of breeding sites within colonies.

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“…The signature of this water mass attenuates to the east [Stein, 1986] and its presence is weak or missing in the central and southern Strait [Gordon and Nowlin, 1978;Makarov et al, 1988]. Several studies [e.g., Sievers, 1982;Capella et al, 1992b] have noted the strong interleaving that occurs at the front that separates oceanic and Bransfield waters and have suggested that this is an important mechanism by which these waters are mixed. [1982] showed that upwelling north of the South Shetland Islands resulted in the injection of CDW into the upper water column.…”

Section: Regional Circulation Modelsmentioning

confidence: 99%

Water mass distribution and circulation west of the Antarctic Peninsula and including Bransfield Strait

Hofmann

Klinck

Lascara

et al. 1996

Antarctic Research Series

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167

166

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Historical hydrographic data from Bransfield Strait and the region west of the Antarctic Peninsula were analyzed to provide descriptions of water mass distributions and circulation patterns. Circumpolar Deep Water (CDW), which is characterized by temperatures above 1.0øC, salinities of 34.6 to 34.73, and oxygen values below 4.5 ml 14, is the most prominent water mass in this region, is found between 200 and 700 m, and is present in all seasons throughout the region examined. Below 200 m this water mass floods the continental shelf west of the Antarctic Peninsula. CDW is also found in Bransfield Strait, but the distribution is limited to the northern side of the Strait near the South Shetland Islands. Mixing of CDW results in reduction of the oxygen content of the overlying waters by 25 to 45%, which suggests an average annual entrainment rate for the west Antarctic Peninsula of 0.7 to 1.43 x 10 '6 m s 4. The freshwater input needed to balance the salinity input from CDW is on the order of 0.63 m y-i, which can be supplied by local precipitation and advection of ice into the region from the Bellingshausen Sea, which then melts. The annual heat flux associated with CDW is 12 W m '2, which is sufficient to melt this amount of ice. A second prominent water mass, Bransfield Strait Water (< 0øC, 34.45 to 34.6), is found throughout the central and southern portions of the Strait. The circulation pattern, constructed from historical data sources, for the region west of the Antarctic Peninsula shows that the large-scale geostrophic flow may be composed of one or more clockwise gyres. This mesoscale variability is likely the result of the rugged bottom topography and has implications for the transport and retention of physical and biological properties. Surface drifters indicate that the circulation in Bransfield Strait is clockwise and may be continuous with the circulation west of the Antarctic Peninsula above 500 m. The circulation pattern inferred from historical temperature distributions suggests that the westward flowing Polar Slope Current, which has been observed north of the South Shetland Islands, does not extend beyond Smith Island. was done in this region until the 1970s when some stations were occupied along the axis of the Bransfield Strait [Gordon and Nowlin, 1978] and along the northern flank of the South Shetland Islands [Nowlin and Clifford, 1982; Sievers and Nowlin, 1984] as part of the International Southern Ocean Studies (ISOS) program. More hydrographic measurements were made in the Bransfield Strait region in the 1980s as part of the First International BIOMASS Experiment (FIBEX) and other Antarctic krill research activities [e.g., Stein, 1983; Stein and Rakusa-Suszczewski, 1983; 19-84]. These studies yielded primarily measurements of temperature distributions in the upper 500 m, but are still useful for characterizing the water column structure in this region. During the Second International BIOMASS Experiment (SIBEX), multidisciplinary cruises were conducted in an expanded study area that included ...

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A note on the thermal structure of the upper ocean in the Bransfield Strait-South Shetland Islands region

Cited by 45 publications

References 3 publications

Ocean circulation and dynamics on the west Antarctic Peninsula continental shelf

Ocean circulation and dynamics on the west Antarctic Peninsula continental shelf

The breeding biology and distribution of Adélie penguins: Adaptations to environmental variability

Water mass distribution and circulation west of the Antarctic Peninsula and including Bransfield Strait

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