The role of water column stability and wind mixing in the production/export dynamics of two bays in the Western Antarctic Peninsula

2019 ◽  
Vol 174 ◽  
pp. 105-116 ◽  
Author(s):  
Juan Höfer ◽  
Ricardo Giesecke ◽  
Mark J. Hopwood ◽  
Vania Carrera ◽  
Emilio Alarcón ◽  
...  
Keyword(s):  
Water Column ◽  
Antarctic Peninsula ◽  
Western Antarctic Peninsula ◽  
Water Column Stability ◽  
Export Dynamics ◽  
Wind Mixing

scholarly journals Water Column Stability and the Role of Velocity Shear on a Seasonally Stratified Shelf, Mississippi Bight, Northern Gulf of Mexico

2018 ◽  
Vol 123 (8) ◽  
pp. 5777-5796 ◽  
Author(s):  
Brian Dzwonkowski ◽  
Severine Fournier ◽  
Kyeong Park ◽  
Steven L. Dykstra ◽  
John T. Reager
Keyword(s):  
Gulf Of Mexico ◽  
Water Column ◽  
Velocity Shear ◽  
Northern Gulf Of Mexico ◽  
Water Column Stability

scholarly journals Spring–summer net community production, new production, particle export and related water column biogeochemical processes in the marginal sea ice zone of the Western Antarctic Peninsula 2012–2014

2018 ◽  
Vol 376 (2122) ◽  
pp. 20170177 ◽  
Author(s):  
Hugh W. Ducklow ◽  
Michael R. Stukel ◽  
Rachel Eveleth ◽  
Scott C. Doney ◽  
Tim Jickells ◽  
...  
Keyword(s):  
Sea Ice ◽  
Primary Production ◽  
Water Column ◽  
Antarctic Peninsula ◽  
Net Primary Production ◽  
Western Antarctic Peninsula ◽  
New Production ◽  
Net Community Production ◽  
Particle Export ◽  
Community Production

New production (New P, the rate of net primary production (NPP) supported by exogenously supplied limiting nutrients) and net community production (NCP, gross primary production not consumed by community respiration) are closely related but mechanistically distinct processes. They set the carbon balance in the upper ocean and define an upper limit for export from the system. The relationships, relative magnitudes and variability of New P (from 15 NO 3 – uptake), O 2  : argon-based NCP and sinking particle export (based on the 238 U :  234 Th disequilibrium) are increasingly well documented but still not clearly understood. This is especially true in remote regions such as polar marginal ice zones. Here we present a 3-year dataset of simultaneous measurements made at approximately 50 stations along the Western Antarctic Peninsula (WAP) continental shelf in midsummer (January) 2012–2014. Net seasonal-scale changes in water column inventories (0–150 m) of nitrate and iodide were also estimated at the same stations. The average daily rates based on inventory changes exceeded the shorter-term rate measurements. A major uncertainty in the relative magnitude of the inventory estimates is specifying the start of the growing season following sea-ice retreat. New P and NCP(O 2 ) did not differ significantly. New P and NCP(O 2 ) were significantly greater than sinking particle export from thorium-234. We suggest this is a persistent and systematic imbalance and that other processes such as vertical mixing and advection of suspended particles are important export pathways. 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 Holocene climate variations in the western Antarctic Peninsula: evidence for sea ice extent predominantly controlled by changes in insolation and ENSO variability

2013 ◽  
Vol 9 (4) ◽  
pp. 1431-1446 ◽  
Author(s):  
J. Etourneau ◽  
L. G. Collins ◽  
V. Willmott ◽  
J.-H. Kim ◽  
L. Barbara ◽  
...  
Keyword(s):  
Sea Ice ◽  
Water Column ◽  
Antarctic Peninsula ◽  
Primary Productivity ◽  
Climatic Factors ◽  
Southern Oscillation ◽  
Western Antarctic Peninsula ◽  
Deep Basin ◽  
Sea Ice Extent ◽  
Ice Conditions

Abstract. The West Antarctic ice sheet is particularly sensitive to global warming and its evolution and impact on global climate over the next few decades remains difficult to predict. In this context, investigating past sea ice conditions around Antarctica is of primary importance. Here, we document changes in sea ice presence, upper water column temperatures (0–200 m) and primary productivity over the last 9000 yr BP (before present) in the western Antarctic Peninsula (WAP) margin from a sedimentary core collected in the Palmer Deep Basin. Employing a multi-proxy approach, based on the combination of two biomarkers proxies (highly branched isoprenoid (HBI) alkenes for sea ice and TEX86L for temperature) and micropaleontological data (diatom assemblages), we derived new Holocene records of sea ice conditions and upper water column temperatures. The early Holocene (9000–7000 yr BP) was characterized by a cooling phase with a short sea ice season. During the mid-Holocene (~7000–3800 yr BP), local climate evolved towards slightly colder conditions and a prominent extension of the sea ice season occurred, promoting a favorable environment for intensive diatom growth. The late Holocene (the last ~2100 yr) was characterized by warmer temperatures and increased sea ice presence, accompanied by reduced local primary productivity, likely in response to a shorter growing season compared to the early or mid-Holocene. The gradual increase in annual sea ice duration over the last 7000 yr might have been influenced by decreasing mean annual and spring insolation, despite increasing summer insolation. We postulate that, in addition to precessional changes in insolation, seasonal variability, via changes in the strength of the circumpolar Westerlies and upwelling activity, was further amplified by the increasing frequency/amplitude of the El Niño–Southern Oscillation (ENSO). However, between 3800 and 2100 yr BP, the lack of correlation between ENSO and climate variability in the WAP suggests that other climatic factors might have been more important in controlling WAP climate at this time.

scholarly journals Holocene climate variations in the western Antarctic Peninsula: evidence for sea ice extent predominantly controlled by insolation and ENSO variability changes

2013 ◽  
Vol 9 (1) ◽  
pp. 1-41 ◽  
Author(s):  
J. Etourneau ◽  
L. G. Collins ◽  
V. Willmott ◽  
J. H. Kim ◽  
L. Barbara ◽  
...  
Keyword(s):  
Sea Ice ◽  
Water Column ◽  
Antarctic Peninsula ◽  
Primary Productivity ◽  
Climatic Factors ◽  
Southern Oscillation ◽  
Western Antarctic Peninsula ◽  
Deep Basin ◽  
Sea Ice Extent ◽  
Ice Conditions

Abstract. The West Antarctic ice sheet is particularly sensitive to global warming and its evolution and impact on global climate over the next few decades remains difficult to predict. In this context, investigating past sea ice conditions around Antarctica is of primary importance. Here, we document changes in sea ice presence, upper water column temperatures (0–200 m) and primary productivity over the last 9000 yr BP (before present) in the western Antarctic Peninsula (WAP) margin from a sedimentary core collected in the Palmer Deep basin. Employing a multi-proxy approach, we derived new Holocene records of sea ice conditions and upper water column temperatures, based on the combination of two biomarkers proxies (highly branched isoprenoid (HBI) alkenes for sea ice and TEXL86 for temperature) and micropaleontological data (diatom assemblages). The early Holocene (9000–7000 yr BP) was characterized by a cooling phase with a short sea ice season. During the mid-Holocene (~ 7000–3000 yr BP), local climate evolved towards slightly colder conditions and a prominent extension of the sea ice season occurred, promoting a favorable environment for intensive diatom growth. The late Holocene (the last ~ 3000 yr) was characterized by more variable temperatures and increased sea ice presence, accompanied by reduced local primary productivity likely in response to a shorter growing season compared to the early or mid-Holocene. The stepwise increase in annual sea ice duration over the last 7000 yr might have been influenced by decreasing mean annual and spring insolation despite an increasing summer insolation. We postulate that in addition to precessional changes in insolation, seasonal variability, via changes in the strength of the circumpolar Westerlies and upwelling activity, was further amplified by the increasing frequency/amplitude of El Niño-Southern Oscillation (ENSO). However, between 4000 and 2100 yr BP, the lack of correlation between ENSO and climate variability in the WAP suggests that other climatic factors might have been more important in controlling WAP climate at this time.

A high resolution relative paleointensity record from the Gerlache-Boyd paleo-ice stream region, northern Antarctic Peninsula

2006 ◽  
Vol 66 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Verónica Willmott ◽  
Eugene W. Domack ◽  
Miquel Canals ◽  
Stefanie Brachfeld
Keyword(s):  
Antarctic Peninsula ◽  
Mineral Assemblage ◽  
Western Antarctic Peninsula ◽  
Suitable Material ◽  
Relative Paleointensity ◽  
Shelf Sediments ◽  
Tephra Layers ◽  
Absolute Dating ◽  
Bransfield Basin

AbstractHerein we document and interpret an absolute chronological dating attempt using geomagnetic paleointensity data from a post-glacial sediment drape on the western Antarctic Peninsula continental shelf. Our results demonstrate that absolute dating can be established in Holocene Antarctic shelf sediments that lack suitable material for radiocarbon dating. Two jumbo piston cores of 10-m length were collected in the Western Bransfield Basin. The cores preserve a strong, stable remanent magnetization and meet the magnetic mineral assemblage criteria recommended for reliable paleointensity analyses. The relative paleomagnetic intensity records were tuned to published absolute and relative paleomagnetic stacks, which yielded a record of the last ∼8500 years for the post-glacial drape. Four tephra layers associated with documented eruptions of nearby Deception Island have been dated at 3.31, 3.73, 4.44, and 6.86 ± 0.07 ka using the geomagnetic paleointensity method. This study establishes the dual role of geomagnetic paleointensity and tephrochronology in marine sediments across both sides of the northern Antarctic Peninsula.

scholarly journals Surface circulation patterns and the pathways of sea surface carbon dioxide (CO<sub>2</sub>) off northern Chile (~27.5° S) between 30 and 10 kyr BP: global and/or local forcing?

2010 ◽  
Vol 6 (2) ◽  
pp. 347-368
Author(s):  
J. A. Placencia ◽  
N. Harada ◽  
R. Torres ◽  
C. B. Lange ◽  
D. Hebbeln
Keyword(s):  
Carbon Sequestration ◽  
Water Column ◽  
Coastal Upwelling ◽  
Isotope Composition ◽  
High Pco2 ◽  
Northern Chile ◽  
Water Column Stability ◽  
Surface Circulation ◽  
Circulation Patterns

Abstract. We present a reconstruction of past changes in partial pressure of CO2 (pCO2) from northern Chile (~27° S), between 10 and 30 kyr BP, based on carbon isotope composition of C37:2-alkenone. The high-pCO2 during the entire time series indicates that northern Chile upwelling system has been a permanent source of CO2 to the atmosphere. The multiproxy reconstruction suggests that the CO2 outgassing and sequestration pathways were modulated by local and global mechanisms. During global glacial conditions, an enhanced coastal upwelling forcing resulted in high-availability of deep water macronutrients and a CO2-supersaturated water column, which combined with high-inputs of iron from the continent, intensified the carbon sequestration pathway of the biological pump, through diatom biomass export. During the deglacial, a decrease in the upwelling forcing, an increment in water column stability and reduced continental inputs of iron are consistent with a larger role of calcifying organisms in the plankton assemblage in terms of carbon sequestration pathway through the carbonate system.

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