scholarly journals A ‘shallow bathtub ring’ of local sedimentary iron input maintains the Palmer Deep biological hotspot on the West Antarctic Peninsula shelf

2018 ◽  
Vol 376 (2122) ◽  
pp. 20170171 ◽  
Author(s):  
Robert M. Sherrell ◽  
Amber L. Annett ◽  
Jessica N. Fitzsimmons ◽  
Vincent J. Roccanova ◽  
Michael P. Meredith
Keyword(s):  
Antarctic Peninsula ◽  
Deep Water ◽  
Rapid Change ◽  
Euphotic Zone ◽  
The West ◽  
Inner Shelf ◽  
West Antarctic ◽  
Limiting Nutrient ◽  
Marine System ◽  
West Antarctic Peninsula

Palmer Deep (PD) is one of several regional hotspots of biological productivity along the inner shelf of the West Antarctic Peninsula. The proximity of hotspots to shelf-crossing deep troughs has led to the ‘canyon hypothesis’, which proposes that circumpolar deep water flowing shoreward along the canyons is upwelled on the inner shelf, carrying nutrients including iron (Fe) to surface waters, maintaining phytoplankton blooms. We present here full-depth profiles of dissolved and particulate Fe and manganese (Mn) from eight stations around PD, sampled in January and early February of 2015 and 2016, allowing the first detailed evaluation of Fe sources to the area's euphotic zone. We show that upwelling of deep water does not control Fe flux to the surface; instead, shallow sediment-sourced Fe inputs are transported horizontally from surrounding coastlines, creating strong vertical gradients of dissolved Fe within the upper 100 m that supply this limiting nutrient to the local ecosystem. The supply of bioavailable Fe is, therefore, not significantly related to the canyon transport of deep water. Near shore time-series samples reveal that local glacial meltwater appears to be an important Mn source but, surprisingly, is not a large direct Fe input to this biological hotspot. This article is part of the theme issue ‘The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change’.

scholarly journals Sensitivity of Circumpolar Deep Water Transport and Ice Shelf Basal Melt along the West Antarctic Peninsula to Changes in the Winds

2012 ◽  
Vol 25 (14) ◽  
pp. 4799-4816 ◽  
Author(s):  
Michael S. Dinniman ◽  
John M. Klinck ◽  
Eileen E. Hofmann
Keyword(s):  
Continental Shelf ◽  
Antarctic Peninsula ◽  
Deep Water ◽  
Constant Factor ◽  
Ice Shelf ◽  
The West ◽  
Ice Shelves ◽  
Circumpolar Deep Water ◽  
West Antarctic ◽  
West Antarctic Peninsula

Abstract Circumpolar Deep Water (CDW) can be found near the continental shelf break around most of Antarctica. Advection of this relatively warm water (up to 2°C) across the continental shelf to the base of floating ice shelves is thought to be a critical source of heat for basal melting in some locations. A high-resolution (4 km) regional ocean–sea ice–ice shelf model of the west Antarctic Peninsula (WAP) coastal ocean was used to examine the effects of changes in the winds on across-shelf CDW transport and ice shelf basal melt. Increases and decreases in the strength of the wind fields were simulated by scaling the present-day winds by a constant factor. Additional simulations considered effects of increased Antarctic Circumpolar Current (ACC) transport. Increased wind strength and ACC transport increased the amount of CDW transported onto the WAP continental shelf but did not necessarily increase CDW flux underneath the nearby ice shelves. The basal melt underneath some of the deeper ice shelves actually decreased with increased wind strength. Increased mixing over the WAP shelf due to stronger winds removed more heat from the deeper shelf waters than the additional heat gained from increased CDW volume transport. The simulation results suggest that the effect on the WAP ice shelves of the projected strengthening of the polar westerlies is not a simple matter of increased winds causing increased (or decreased) basal melt. A simple budget calculation indicated that iron associated with increased vertical mixing of CDW could significantly affect biological productivity of this region.

scholarly journals Oceanographic variability on the West Antarctic Peninsula during the Holocene and the influence of upper circumpolar deep water

2015 ◽  
Vol 119 ◽  
pp. 54-65 ◽  
Author(s):  
Victoria L. Peck ◽  
Claire S. Allen ◽  
Sev Kender ◽  
Erin L. McClymont ◽  
Dominic A. Hodgson
Keyword(s):  
Antarctic Peninsula ◽  
Deep Water ◽  
The West ◽  
The Holocene ◽  
Circumpolar Deep Water ◽  
West Antarctic ◽  
West Antarctic Peninsula

scholarly journals Macronutrient and carbon supply, uptake and cycling across the Antarctic Peninsula shelf during summer

2018 ◽  
Vol 376 (2122) ◽  
pp. 20170168 ◽  
Author(s):  
Sian F. Henley ◽  
Elizabeth M. Jones ◽  
Hugh J. Venables ◽  
Michael P. Meredith ◽  
Yvonne L. Firing ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Inorganic Carbon ◽  
Carbon Sink ◽  
Significant Proportion ◽  
Rapid Change ◽  
The West ◽  
Carbon Supply ◽  
West Antarctic ◽  
Shelf Sediment ◽  
West Antarctic Peninsula

The West Antarctic Peninsula shelf is a region of high seasonal primary production which supports a large and productive food web, where macronutrients and inorganic carbon are sourced primarily from intrusions of warm saline Circumpolar Deep Water. We examined the cross-shelf modification of this water mass during mid-summer 2015 to understand the supply of nutrients and carbon to the productive surface ocean, and their subsequent uptake and cycling. We show that nitrate, phosphate, silicic acid and inorganic carbon are progressively enriched in subsurface waters across the shelf, contrary to cross-shelf reductions in heat, salinity and density. We use nutrient stoichiometric and isotopic approaches to invoke remineralization of organic matter, including nitrification below the euphotic surface layer, and dissolution of biogenic silica in deeper waters and potentially shelf sediment porewaters, as the primary drivers of cross-shelf enrichments. Regenerated nitrate and phosphate account for a significant proportion of the total pools of these nutrients in the upper ocean, with implications for the seasonal carbon sink. Understanding nutrient and carbon dynamics in this region now will inform predictions of future biogeochemical changes in the context of substantial variability and ongoing changes in the physical environment. This article is part of the theme issue ‘The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change’.

scholarly journals Variability and change in the west Antarctic Peninsula marine system: Research priorities and opportunities

2019 ◽  
Vol 173 ◽  
pp. 208-237 ◽  
Author(s):  
Sian F. Henley ◽  
Oscar M. Schofield ◽  
Katharine R. Hendry ◽  
Irene R. Schloss ◽  
Deborah K. Steinberg ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Research Priorities ◽  
System Research ◽  
The West ◽  
West Antarctic ◽  
Marine System ◽  
West Antarctic Peninsula

scholarly journals Evidences of strong sources of DFe and DMn in Ryder Bay, Western Antarctic Peninsula

2018 ◽  
Vol 376 (2122) ◽  
pp. 20170172 ◽  
Author(s):  
Johann Bown ◽  
Hans van Haren ◽  
Michael P. Meredith ◽  
Hugh J. Venables ◽  
Patrick Laan ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Sediment Resuspension ◽  
Vertical Mixing ◽  
Rapid Change ◽  
Austral Summer ◽  
Bottom Surface ◽  
The West ◽  
West Antarctic ◽  
Deep Waters ◽  
West Antarctic Peninsula

The spatial distribution, biogeochemical cycling and external sources of dissolved iron and dissolved manganese (DFe and DMn) were investigated in Ryder Bay, a small coastal embayment of the West Antarctic Peninsula, during Austral summer (2013 and 2014). Dissolved concentrations were measured throughout the water column at 11 stations within Ryder Bay. The concentration ranges of DFe and DMn were large, between 0.58 and 32.7 nM, and between 0.18 and 26.2 nM, respectively, exhibiting strong gradients from the surface to the bottom. Surface concentrations of DFe and DMn were higher than concentrations reported for the Southern Ocean and coastal Antarctic waters, and extremely high concentrations were detected in deep water. Glacial meltwater and shallow sediments are likely to be the main sources of DFe and DMn in the euphotic zone, while lateral advection associated with local sediment resuspension and vertical mixing are significant sources for intermediate and deep waters. During summer, vertical mixing of intermediate and deep waters and sediment resuspension occurring from Marguerite Trough to Ryder Bay are thought to be amplified by a series of overflows at the sills, enhancing the input of Fe and Mn from bottom sediment and increasing their concentrations up to the euphotic layer. This article is part of the theme issue ‘The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change’.

Variability of warm water intrusions onto the Bellingshausen Sea continental shelf

2021 ◽  
Author(s):  
Ria Oelerich ◽  
Karen J. Heywood ◽  
Gillian M. Damerell ◽  
Andrew F. Thompson
Keyword(s):  
Continental Shelf ◽  
Continental Slope ◽  
Antarctic Peninsula ◽  
Deep Water ◽  
Warm Water ◽  
The West ◽  
Ice Shelves ◽  
West Antarctic ◽  
Bellingshausen Sea ◽  
West Antarctic Peninsula

<p>The continental shelf of the Bellingshausen Sea, located between the West Antarctic Peninsula and the Amundsen Sea, Antarctica, is poorly investigated, compared with its neighbours. Here, the southernmost frontal jet of the Antarctic Circumpolar Current is adjacent to the continental slope which impacts the transport of warm Circumpolar Deep Water onto the shelf. This in turn can influence the transport of heat southward across the shelf and therefore the melting of vulnerable ice shelves.</p><p>We present model-based investigations using the GLORYS12V1 1/12° reanalysis monthly output (GLOBAL_REANALYSIS_PHY_001_030) over 19 years from 2000 to 2018. By connecting the location of the frontal jet to SSH contours we identify seasonal and interannual variability in this current system and demonstrate that the closer the frontal jet is to the continental slope, the greater the flow of warm deep water onto the shelf. This onshore flow is limited to specific areas closest to the frontal jet, predominantly in the eastern Bellingshausen Sea. In contrast, other areas, specifically those troughs where water flows towards the West Antarctic Peninsula and close to the coastline of Antarctica show opposite behaviour with respect to onshelf heat content. Further analyses of flow patterns also indicate the involvement of a coastal jet close to the shore that is weaker when more warm water is on the shelf. Understanding the variability in the current structures throughout the continental shelf of the Bellingshausen Sea in response to a changing frontal jet is essential to gain knowledge about the distribution of heat and therefore the melting of ice shelves.</p>

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