scholarly journals Mapping the Antarctic Polar Front: weekly realizations from 2002 to 2014

2016 ◽  
Vol 8 (1) ◽  
pp. 191-198 ◽  
Author(s):  
Natalie M. Freeman ◽  
Nicole S. Lovenduski
Keyword(s):  
Southern Ocean ◽  
Bottom Topography ◽  
Drake Passage ◽  
Polar Front ◽  
Average Intensity ◽  
Antarctic Polar Front ◽  
Data Set ◽  
Latitudinal Position ◽  
Microwave Radiometers ◽  
The Antarctic

Abstract. We map the weekly position of the Antarctic Polar Front (PF) in the Southern Ocean over a 12-year period (2002–2014) using satellite sea surface temperature (SST) estimated from cloud-penetrating microwave radiometers. Our study advances previous efforts to map the PF using hydrographic and satellite data and provides a unique realization of the PF at weekly resolution across all longitudes (doi:10.1594/PANGAEA.855640). The mean path of the PF is asymmetric; its latitudinal position spans from 44 to 64° S along its circumpolar path. SST at the PF ranges from 0.6 to 6.9 °C, reflecting the large spread in latitudinal position. The average intensity of the front is 1.7 °C per 100 km, with intensity ranging from 1.4 to 2.3 °C per 100 km. Front intensity is significantly correlated with the depth of bottom topography, suggesting that the front intensifies over shallow bathymetry. Realizations of the PF are consistent with the corresponding surface expressions of the PF estimated using expendable bathythermograph data in the Drake Passage and Australian and African sectors. The climatological mean position of the PF is similar, though not identical, to previously published estimates. As the PF is a key indicator of physical circulation, surface nutrient concentration, and biogeography in the Southern Ocean, future studies of physical and biogeochemical oceanography in this region will benefit from the provided data set.

scholarly journals Mapping the Antarctic Polar Front: Weekly realizations from 2002 to 2014

2016 ◽  
Author(s):  
Natalie M. Freeman ◽  
Nicole S. Lovenduski
Keyword(s):  
Southern Ocean ◽  
Bottom Topography ◽  
Drake Passage ◽  
Polar Front ◽  
Average Intensity ◽  
Antarctic Polar Front ◽  
Data Set ◽  
Latitudinal Position ◽  
Microwave Radiometers ◽  
The Antarctic

Abstract. We map the weekly position of the Antarctic Polar Front (PF) in the Southern Ocean over a 12-year period (2002–2014) using satellite sea surface temperature (SST) estimated from cloud-penetrating microwave radiometers. Our study advances previous efforts to map the PF using hydrographic and satellite data and provides a unique realization of the PF at weekly resolution across all longitudes (doi:10.1594/PANGAEA.855640). The mean path of the PF is asymmetric; its latitudinal position spans from 44 to 64° S along its circumpolar path. SST at the PF ranges from 0.6 to 6.9 °C, reflecting the large spread in latitudinal position. The average intensity of the front is 1.7 °C per 100 km, with intensity ranging from 1.4 to 2.3 °C per 100 km. Front intensity is significantly correlated with the depth of bottom topography, suggesting that the front intensifies over shallow bathymetry. Realizations of the PF are consistent with the corresponding surface expressions of the PF estimated using expendable bathythermograph data in the Drake Passage and Australian and African sectors. The climatological mean position of the PF is similar, though not identical, to previously published estimates. As the PF is a key indicator of physical circulation, surface nutrient concentration, and biogeography in the Southern Ocean, future studies of physical and biogeochemical oceanography in this region will benefit from the provided data set.

scholarly journals Winter Biogeochemical Cycling of Dissolved and Particulate Cadmium in the Indian Sector of the Southern Ocean (GEOTRACES GIpr07 Transect)

2021 ◽  
Vol 8 ◽  
Author(s):  
Ryan Cloete ◽  
Jean C. Loock ◽  
Natasha R. van Horsten ◽  
Susanne Fietz ◽  
Thato N. Mtshali ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Biogeochemical Cycling ◽  
Polar Front ◽  
Water Masses ◽  
Antarctic Polar Front ◽  
Intermediate Water ◽  
Subtropical Zone ◽  
Near Surface ◽  
The Antarctic ◽  
Indian Sector

Winter distributions of dissolved cadmium (dCd) and particulate cadmium (pCd) were measured for the first time in the Indian sector of the Southern Ocean thereby contributing a unique spatial and seasonal dataset. Seven depth profiles, between 41°S and 58°S, were collected along the 30°E longitude during the 2017 austral winter to investigate the biogeochemical cycling of cadmium during a period characterized by contrasting upper water column dynamics compared to summer. Our results support an important role for biological uptake during winter months albeit weaker compared to summer. Distinct, biologically driven changes in cadmium cycling across the transect were observed. For example, surface ratios of pCd to phosphorus (P; pCd:P) increased from 0.37 to 1.07 mmol mol–1 between the subtropical zone (STZ) and the Antarctic zone (AAZ) reflecting increased Cd requirements for diatoms at higher latitudes which, in turn, was driven by a complex relationship between the availability of dCd and dissolved iron (dFe), zinc (dZn) and manganese (dMn). Vertical profiles of pCd:P displayed near-surface maxima consistent with (1) P occurring in two phases with different labilities and the lability of Cd being somewhere in-between and (2) increasing dCd to phosphate (PO4; dCd:PO4) ratios with depth at each station. North of the Antarctic Polar Front (APF), a secondary, deeper pCd:P maximum may reflect an advective signal associated with northward subducting Antarctic Intermediate Water (AAIW). The strong southward increase in surface dCd and dCd:PO4, from approximately 10–700 pmol kg–1 and 40–400 μmol mol–1, respectively, reflected the net effect of preferential uptake and regeneration of diatoms with high Cd content and the upwelling of Cd enriched water masses in the AAZ. Furthermore, distinct dCd versus PO4 relationships were observed in each of the intermediate and deep water masses suggesting that dCd and PO4 distributions at depth are largely the result of physical water mass mixing.

IBCSO V2.0: An updated Antarctic bathymetry product of Seabed 2030

2020 ◽  
Author(s):  
Laura Hehemann ◽  
Jan Erik Arndt ◽  
Boris Dorschel
Keyword(s):  
Southern Ocean ◽  
Ice Sheets ◽  
Drake Passage ◽  
Ocean Current ◽  
Detailed Knowledge ◽  
Data Set ◽  
Seafloor Morphology ◽  
Almost All ◽  
The Antarctic ◽  
First Time

<p>The International Bathymetric Chart of the Southern Ocean (IBCSO), part of the Nippon Foundation – GEBCO – Seabed 2030 project, is a collaborative effort to create high-resolution bathymetric compilations off Antarctica. Detailed knowledge of seafloor morphology is fundamental to almost all marine and maritime scientific activities. For example, it can be used to understand past glacial development, to create habitat models and maps, and to identify ocean current pathways that may contribute to increased basal melt of the Antarctic ice sheets. In comparison to IBCSO V1.0, which extended to 60° south, the new version now extends up to 50° south increasing the ocean area by a factor of approximately 2.5. With this extension, the new bathymetric model will include important submarine features like the Drake Passage, the South Sandwich Arc, and the southern parts of the Kerguelen Plateau and Campbell Plateau. IBCSO continues to build on the on the largest database of bathymetric soundings for the Southern Ocean that was gathered by a variety of international institutions. We will present the new IBCSO V2.0 data set for the first time and will highlight its improvement in comparison to its predecessor.</p>

scholarly journals The anatomy of the Antarctic polar front in the Drake Passage

1978 ◽  
Vol 83 (C12) ◽  
pp. 6093 ◽  
Author(s):  
Terrence M. Joyce ◽  
Walter Zenk ◽  
John M. Toole
Keyword(s):  
Drake Passage ◽  
Polar Front ◽  
Antarctic Polar Front ◽  
The Antarctic

scholarly journals Distribution of short-finned squid Illex argentinus (Cephalopoda: Ommastrephidae) inferred from the diets of Southern Ocean albatrosses using stable isotope analyses

2015 ◽  
Vol 96 (6) ◽  
pp. 1211-1215 ◽  
Author(s):  
José Seco ◽  
Gustavo A. Daneri ◽  
Filipe R. Ceia ◽  
Rui Pedro Vieira ◽  
Simeon L. Hill ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Southern Ocean ◽  
Polar Front ◽  
Antarctic Polar Front ◽  
Stable Isotope Analyses ◽  
Patagonian Shelf ◽  
Illex Argentinus ◽  
Shelf Region ◽  
The Antarctic ◽  
Isotope Analyses

The diets of marine predators are a potential source of information about range shifts in their prey. For example, the short-finned squid Illex argentinus, a commercially fished species on the Patagonian Shelf in the South Atlantic, has been reported in the diet of grey-headed, Thalassarche chrysostoma; black-browed, T. melanophris; and wandering, Diomedea exulans, albatrosses breeding at Bird Island, South Georgia (54°S 28°W) in the Southern Ocean. Tracking data suggest that these birds may feed on I. argentinus while foraging in Southern Ocean waters during their breeding season. This led to the hypothesis that I. argentinus may occur south of the Antarctic Polar Front. To test this hypothesis, we used stable isotope analyses to assess the origin of I. argentinus. We compared I. argentinus beaks from the diets of the three albatross species with beaks of cephalopod species endemic to the Patagonian Shelf and others from the Southern Ocean. Our results show that I. argentinus from the diet of albatrosses at Bird Island have δ13C values in the range −18.77 to −15.28‰. This is consistent with δ13C values for Octopus tehuelchus, a typical species from the Patagonian Shelf. In contrast, Alluroteuthis antarcticus, a Southern Ocean squid, has typically Antarctic δ13C in the range −25.46 to −18.61‰. This suggests that I. argentinus originated from warmer waters of the Patagonian Shelf region. It is more likely that the albatross species obtained I. argentinus by foraging in the Patagonian Shelf region than that I. argentinus naturally occurs south of the Antarctic Polar Front.

Dissolution and Preservation of Antarctic Diatoms and the Effect on Sediment Thanatocoenoses

1989 ◽  
Vol 31 (2) ◽  
pp. 288-308 ◽  
Author(s):  
A. Shemesh ◽  
L. H. Burckle ◽  
P. N. Froelich
Keyword(s):  
Southern Ocean ◽  
Transfer Functions ◽  
Polar Front ◽  
Antarctic Polar Front ◽  
Diatom Assemblages ◽  
Differential Dissolution ◽  
Surface Ocean ◽  
Antarctic Diatoms ◽  
The Antarctic ◽  
The Last Glacial

AbstractComparison of Southern Ocean diatom populations from (i) surface ocean production, (ii) underlying Antarctic sediments, and (iii) laboratory dissolution experiments demonstrates that dissolution can account for the temporal and spatial variations in sedimentary diatom assemblages observed in Southern Ocean sediments. Increasing dissolution causes relative depletions in N. kerguelensis (K), enrichments in T. lentiginosa (L), and slight enrichments in E. antarctica (A). This reflects the relative susceptibility to dissolution of the three species that dominate Antarctic sediments. We have devised a preservation index for the Southern Ocean based on the ratio K/(K + L) to estimate relative extents of dissolution and applied it to natural assemblages. Holocene Southern Ocean sediments display increasing opal preservation toward higher latitudes, but south of the Antarctic Polar Front preservation decreases in the order: well preserved = SE Indian > S. Atlantic ∼ SW Indian > SE Pacific = poorly preserved. Dissolution also accounts for the pattern of diatom assemblages in the last glacial maximum (LGM) sediments of the Indian and Pacific sectors, but in the Atlantic, increased E. antarctica abundances at LGM must have resulted from an increase in surface ocean production of this species. Holocene and LGM diatoms in Atlantic and Pacific sector sediments are equally well preserved, but in the Indian sectors, Holocene sediments are better preserved than those of LGM age. Paleoceanographic and paleoclimatic transfer functions derived from factor analyses of variations in the sedimentary abundances of these three diatoms have ignored the effects of differential dissolution on thanatocoenosis and thus should be interpreted with caution.

scholarly journals Humpback whale abundance south of 60°S from three complete circumpolar sets of surveys

2020 ◽  
pp. 53-69
Author(s):  
T. A. Branch
Keyword(s):  
Ross Sea ◽  
Austral Summer ◽  
Polar Front ◽  
Humpback Whales ◽  
Antarctic Polar Front ◽  
Breeding Ground ◽  
Abundance Estimates ◽  
Rate Of Increase ◽  
Latitudinal Position ◽  
The Antarctic

Austral summer estimates of abundance are obtained for humpback whales (Megaptera novaeangliae) in the Southern Ocean from the IWC’s IDCR and SOWER circumpolar programmes. These surveys have encircled the Antarctic three times: 1978/79–1983/84 (CPI), 1985/86–1990/91 (CPII) and 1991/92–2003/04 (CPIII), criss-crossing strata totalling respectively 64.3%, 79.5% and 99.7% of the open-ocean area south of 60°S. Humpback whales were absent from the Ross Sea, but were sighted in all other regions, and in particularly high densities around the Antarctic Peninsula, in Management Area IV and north of the Ross Sea. Abundance estimates are presented for each CP, for Management Areas, and for assumed summer feeding regions of each Breeding Stock. Abundance estimates are negatively biased because some whales on the trackline are missed and because some humpback whales are outside the survey region. Circumpolar estimates with approximate midpoints of 1980/81, 1987/88 and 1997/98 are 7,100 (CV = 0.36), 10,200 (CV = 0.30) and 41,500 (CV = 0.11). When these are adjusted simply for unsurveyed northern areas, the estimated annual rate of increase is 9.6% (95% CI 5.8–13.4%). All Breeding Stocks are estimated to be increasing but increase rates are significantly greater than zero only for those on the eastern and western coasts of Australia. Given the observed rates of increase, the current total Southern Hemisphere abundance is greater than 55,000, which is similar to the summed northern breeding ground estimates (~60,000 from 1999–2008). Some breeding ground abundance estimates are far greater, and others far lower, than the corresponding IDCR/SOWER estimates, in a pattern apparently related to the latitudinal position of the Antarctic Polar Front.

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