Variability of the Atmospheric Circulation over the Drake Passage, Scotia Sea and Weddell Sea

AbstractUncertainty about the structure of the Falkland Plateau Basin has long hindered understanding of tectonic evolution in southwest Gondwana. New aeromagnetic data from the basin reveal Jurassic-onset seafloor spreading by motion of a single newly-recognized plate, Skytrain, which also governed continental extension in the Weddell Sea Embayment and possibly further afield in Antarctica. The Skytrain plate resolves a nearly century-old controversy by requiring a South American setting for the Falkland Islands in Gondwana. The Skytrain plate’s later motion provides a unifying context for post-Cambrian wide-angle paleomagnetic rotation, Cretaceous uplift, and post-Permian oblique collision in the Ellsworth Mountains of Antarctica. Further north, the Skytrain plate’s margins built a continuous conjugate ocean to the Weddell Sea in the Falkland Plateau Basin and central Scotia Sea. This ocean rules out venerable correlation-based interpretations for a Pacific margin location and subsequent long-distance translation of the South Georgia microcontinent as the Drake Passage gateway opened.

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Dissolved Fe across the Weddell Sea and Drake Passage: impact of DFe on nutrients uptake in the Weddell Sea

Biogeosciences Discussions ◽

10.5194/bgd-10-7433-2013 ◽

2013 ◽

Vol 10 (4) ◽

pp. 7433-7489 ◽

Cited By ~ 3

Author(s):

M. B. Klunder ◽

P. Laan ◽

H. J. W. De Baar ◽

I. Neven ◽

R. Middag ◽

...

Keyword(s):

Deep Water ◽

Bottom Water ◽

Drake Passage ◽

Weddell Sea ◽

Dust Deposition ◽

Scotia Sea ◽

Ice Melt ◽

Sea Bottom ◽

Poc Export ◽

Bottom Waters

Abstract. This manuscript reports the first full depth distributions of dissolved iron (DFe) over a high resolution Weddell Sea and Drake Passage transect. Very low dissolved DFe concentrations (0.01–0.1 nM range) were observed in the surface waters in the Weddell Sea, and within the Polar regime in the Drake Passage. Locally, enrichment in surface DFe was observed, likely due to recent ice melt (Weddell Sea) or dust deposition (Drake Passage). In the Weddell Sea, the low DFe concentrations can be partly explained by high POC export and/or primary production (indicated by chlorophyll fluorescence). As expected, in high DFe regions a strong silicate drawdown compared to nitrate drawdown was observed. However, this difference in drawdown between these nutrients appears not related to biological activity on the Peninsula shelf. In the Western Weddell Sea transect, with relatively small diatoms, no relationship between N:P and N:Si removal ratios and DFe was observed. For comparison, nutrient depletion is also presented for a transect along the Greenwich Meridian (Klunder et al., 2011), where diatoms are significantly larger, the N:P and N:Si removal ratio increased with increasing DFe. These findings confirm the important role of DFe in Southern Ocean (biologically mediated) nutrient cycles. Over the shelf around the Antarctic Peninsula, higher DFe concentrations (> 1.5 nM) were observed. These elevated concentrations of Fe were transported into Drake Passage along isopycnal surfaces. At the South American continent, high (> 2 nM) DFe concentrations were caused by fluvial/glacial input of DFe. On the Weddell Sea side of the Peninsula region, formation of deep water (by downslope convection) caused relatively high Fe (0.6–0.8 nM) concentrations in the bottom waters relative to the water masses at mid depth (0.2–0.4 nM). During transit of Weddell Sea Bottom Water to Drake Passage, through the Scotia Sea, extra DFe is taken up from seafloor sources, resulting in highest bottom water concentrations in the southernmost part of the Drake Passage of > 1 nM. The Weddell Sea Deep Water concentrations (~ 0.32 nM) were consistent with the lowest DFe concentrations observed in Atlantic AABW.

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Dissolved Fe across the Weddell Sea and Drake Passage: impact of DFe on nutrient uptake

Biogeosciences ◽

10.5194/bg-11-651-2014 ◽

2014 ◽

Vol 11 (3) ◽

pp. 651-669 ◽

Cited By ~ 30

Author(s):

M. B. Klunder ◽

P. Laan ◽

H. J. W. De Baar ◽

R. Middag ◽

I. Neven ◽

...

Keyword(s):

Deep Water ◽

Bottom Water ◽

Drake Passage ◽

Weddell Sea ◽

Dust Deposition ◽

Scotia Sea ◽

Ice Melt ◽

Sea Bottom ◽

Phytoplankton Communities ◽

The Difference

Abstract. This manuscript reports the first full depth distributions of dissolved iron (DFe) over a high-resolution Weddell Sea and Drake Passage transect. Very low dissolved DFe concentrations (0.01–0.1 nM range) were observed in the surface waters of the Weddell Sea, and within the Drake Passage polar regime. Locally, enrichment in surface DFe was observed, likely due to recent ice melt (Weddell Sea) or dust deposition (Drake Passage). As expected, in low DFe regions, usually a small silicate drawdown compared to the nitrate drawdown was observed. However, the difference in drawdown between these nutrients appeared not related to DFe availability in the western Weddell Sea. In this region with relatively small diatoms, no relationship between N : P and N : Si removal ratios and DFe was observed. In comparison, along the Greenwich Meridian (Klunder et al., 2011a), where diatoms are significantly larger, the N : P and N : Si removal ratios did increase with increasing DFe. These findings confirm the important role of DFe in biologically mediated nutrient cycles in the Southern Ocean and imply DFe availability might play a role in shaping phytoplankton communities and constraining cell sizes. Over the shelf around the Antarctic Peninsula, higher DFe concentrations (>1.5 nM) were observed. These elevated concentrations of Fe were transported into Drake Passage along isopycnal surfaces. Near the South American continent, high (>2 nM) DFe concentrations were caused by fluvial/glacial input of DFe. On the Weddell Sea side of the Peninsula region, formation of deep water (by downslope convection) caused relatively high Fe (0.6–0.8 nM) concentrations in the bottom waters relative to the water masses at mid-depth (0.2–0.4 nM). During transit of Weddell Sea Bottom Water to the Drake Passage, through the Scotia Sea, additional DFe is taken up from seafloor sources, resulting in highest bottom water concentrations in the southernmost part of the Drake Passage in excess of 1 nM. The Weddell Sea Deep Water concentrations (∼0.32 nM) were consistent with the lowest DFe concentrations observed in Antarctic bottom water in the Atlantic Ocean.

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The distribution of biogenic and lithogenic silica and the composition of particulate organic matter in the Scotia sea and the Drake passage during autumn 1987

Deep Sea Research Part A Oceanographic Research Papers ◽

10.1016/0198-0149(90)90009-k ◽

1990 ◽

Vol 37 (5) ◽

pp. 833-851 ◽

Cited By ~ 27

Author(s):

Paul Treguer ◽

David M. Nelson ◽

Stéphanie Gueneley ◽

Christiane Zeyons ◽

Jean Morvan ◽

...

Keyword(s):

Organic Matter ◽

Particulate Organic Matter ◽

Drake Passage ◽

Scotia Sea

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Western Scotia Sea margins: Improved constraints on the opening of the Drake Passage

Journal of Geophysical Research Atmospheres ◽

10.1029/2006jb004361 ◽

2006 ◽

Vol 111 (B6) ◽

pp. n/a-n/a ◽

Cited By ~ 14

Author(s):

Emanuele Lodolo ◽

Federica Donda ◽

Alejandro Tassone

Keyword(s):

Drake Passage ◽

Scotia Sea

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Geodynamic implications of the Cenozoic stress field on Seymour Island, West Antarctica

Antarctic Science ◽

10.1017/s0954102007000892 ◽

2008 ◽

Vol 20 (2) ◽

pp. 173-184 ◽

Cited By ~ 2

Author(s):

A. Maestro ◽

J. López-Martínez ◽

F. Bohoyo ◽

M. Montes ◽

F. Nozal ◽

...

Keyword(s):

Stress Field ◽

Antarctic Peninsula ◽

Horizontal Stress ◽

Weddell Sea ◽

Scotia Sea ◽

Compressional Stress ◽

The North ◽

Stress States ◽

Bransfield Basin ◽

Minimum Horizontal Stress

AbstractPalaeostress inferred from brittle mesostructures in Seymour (Marambio) Island indicates a Cenozoic to Recent origin for an extensional stress field, with only local compressional stress states. Minimum horizontal stress (σ3) orientations are scattered about two main NE–SW and NW–SE modes suggesting that two stress sources have been responsible for the dominant minimum horizontal stress directions in the north-western Weddell Sea. Extensional structures within a broad-scale compressional stress field can be linked to both the decrease in relative stress magnitudes from active margins to intraplate regions and the rifting processes that occurred in the northern Weddell Sea. Stress states with NW–SE trending σ3are compatible with back-arc extension along the eastern Antarctic Peninsula. We interpret this as due to the opening of the Larsen Basin during upper Cretaceous to Eocene and to the spreading, from Pliocene to present, of the Bransfield Basin (western Antarctic Peninsula), both due to former Phoenix Plate subduction under the Antarctic Plate. NE–SW σ3orientations could be expressions of continental fragmentation of the northern Antarctic Peninsula controlling eastwards drifting of the South Orkney microcontinent and other submerged continental blocks of the southern Scotia Sea.

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