scholarly journals ENSO and variability of the Antarctic Peninsula pelagic marine ecosystem

2008 ◽  
Vol 21 (2) ◽  
pp. 135-148 ◽  
Author(s):  
Valerie J. Loeb ◽  
Eileen E. Hofmann ◽  
John M. Klinck ◽  
Osmund Holm-Hansen ◽  
Warren B. White
Keyword(s):  
Sea Ice ◽  
Antarctic Peninsula ◽  
Antarctic Circumpolar Current ◽  
Southern Oscillation ◽  
Marine Ecosystem ◽  
Weddell Sea ◽  
Enso Variability ◽  
Decadal Scale ◽  
Circumpolar Current ◽  
The Antarctic

AbstractThe West Antarctic Peninsula region is an important source of Antarctic krill (Euphausia superba) in the Southern Ocean. From 1980–2004 abundance and concentration of phytoplankton and zooplankton, krill reproductive and recruitment success and seasonal sea ice extent here were significantly correlated with the atmospheric Southern Oscillation Index and exhibited three- to five-year frequencies characteristic of El Niño–Southern Oscillation (ENSO) variability. This linkage was associated with movements of the Southern Antarctic Circumpolar Current Front and Boundary, a changing influence of Antarctic Circumpolar Current and Weddell Sea waters, and eastward versus westward flow and mixing processes that are consistent with forcing by the Antarctic Dipole high-latitude climate mode. Identification of hydrographic processes underlying ecosystem variability presented here were derived primarily from multi-disciplinary data collected during 1990–2004, a period with relatively stable year-to-year sea ice conditions. These results differ from the overwhelming importance of seasonal sea ice development previously established using 1980–1996 data, a period marked by a major decrease in sea ice from the Antarctic Peninsula region in the late 1980s. These newer results reveal the more subtle consequences of ENSO variability on biological responses. They highlight the necessity of internally consistent long-term multidisciplinary datasets for understanding ecosystem variability and ultimately for establishing well-founded ecosystem management. Furthermore, natural environmental variability associated with interannual- and decadal-scale changes in ENSO forcing must be considered when assessing impacts of climate warming in the Antarctic Peninsula–Weddell Sea region.

scholarly journals Shelf–ocean exchange and hydrography west of the Antarctic Peninsula: a review

2018 ◽  
Vol 376 (2122) ◽  
pp. 20170164 ◽  
Author(s):  
C. Moffat ◽  
M. Meredith
Keyword(s):  
Sea Ice ◽  
Antarctic Peninsula ◽  
Southern Oscillation ◽  
Numerical Models ◽  
Weddell Sea ◽  
The West ◽  
West Antarctic ◽  
West Antarctic Peninsula ◽  
The Antarctic

The West Antarctic Peninsula (WAP) is a highly productive marine ecosystem where extended periods of change have been observed in the form of glacier retreat, reduction of sea-ice cover and shifts in marine populations, among others. The physical environment on the shelf is known to be strongly influenced by the Antarctic Circumpolar Current flowing along the shelf slope and carrying warm, nutrient-rich water, by cold waters flooding into the northern Bransfield Strait from the Weddell Sea, by an extensive network of glaciers and ice shelves, and by strong seasonal to inter-annual variability in sea-ice formation and air–sea interactions, with significant modulation by climate modes like El Niño–Southern Oscillation and the Southern Annular Mode. However, significant gaps have remained in understanding the exchange processes between the open ocean and the shelf, the pathways and fate of oceanic water intrusions, the shelf heat and salt budgets, and the long-term evolution of the shelf properties and circulation. Here, we review how recent advances in long-term monitoring programmes, process studies and newly developed numerical models have helped bridge these gaps and set future research challenges for the WAP system. 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 Coupling Influences of ENSO and PDO on the Inter-Decadal SST Variability of the ACC around the Western South Atlantic

2019 ◽  
Vol 11 (18) ◽  
pp. 4853
Author(s):  
You-Lin Wang ◽  
Yu-Chen Hsu ◽  
Chung-Pan Lee ◽  
Chau-Ron Wu
Keyword(s):  
Antarctic Circumpolar Current ◽  
Water Mass ◽  
Southern Oscillation ◽  
Drake Passage ◽  
South Atlantic ◽  
Sst Variability ◽  
The Pacific ◽  
Circumpolar Current ◽  
The Antarctic

The Antarctic Circumpolar Current (ACC) plays an important role in the climate as it balances heat energy and water mass between the Pacific and Atlantic Oceans through the Drake Passage. However, because the historical measurements and observations are extremely limited, the decadal and long-term variations of the ACC around the western South Atlantic Ocean are rarely studied. By analyzing reconstructed sea surface temperatures (SSTs) in a 147-year period (1870–2016), previous studies have shown that SST anomalies (SSTAs) around the Antarctic Peninsula and South America had the same phase change as the El Niño Southern Oscillation (ENSO). This study further showed that changes in SSTAs in the regions mentioned above were enlarged when the Pacific Decadal Oscillation (PDO) and the ENSO were in the same warm or cold phase, implying that changes in the SST of higher latitude oceans could be enhanced when the influence of the ENSO is considered along with the PDO.

Recent glacial advance in the western Weddell Sea Sector driven by anomalous sea ice circulation

2020 ◽  
Author(s):  
Frazer Christie ◽  
Toby Benham ◽  
Julian Dowdeswell
Keyword(s):  
Sea Ice ◽  
Antarctic Peninsula ◽  
Ice Sheet ◽  
Weddell Sea ◽  
Landsat 8 ◽  
Ice Shelf ◽  
Total Contribution ◽  
Antarctic Ice Sheet ◽  
Ice Shelves ◽  
The Antarctic

<p>The Antarctic Peninsula is one of the most rapidly warming regions on Earth. There, the recent destabilization of the Larsen A and B ice shelves has been directly attributed to this warming, in concert with anomalous changes in ocean circulation. Having rapidly accelerated and retreated following the demise of Larsen A and B, the inland glaciers once feeding these ice shelves now form a significant proportion of Antarctica’s total contribution to global sea-level rise, and have become an exemplar for the fate of the wider Antarctic Ice Sheet under a changing climate. Together with other indicators of glaciological instability observable from satellites, abrupt pre-collapse changes in ice shelf terminus position are believed to have presaged the imminent disintegration of Larsen A and B, which necessitates the need for routine, close observation of this sector in order to accurately forecast the future stability of the Antarctic Peninsula Ice Sheet. To date, however, detailed records of ice terminus position along this region of Antarctica only span the observational period c.1950 to 2008, despite several significant changes to the coastline over the last decade, including the calving of giant iceberg A-68a from Larsen C Ice Shelf in 2017.</p><p>Here, we present high-resolution, annual records of ice terminus change along the entire western Weddell Sea Sector, extending southwards from the former Larsen A Ice Shelf on the eastern Antarctic Peninsula to the periphery of Filchner Ice Shelf. Terminus positions were recovered primarily from Sentinel-1a/b, TerraSAR-X and ALOS-PALSAR SAR imagery acquired over the period 2009-2019, and were supplemented with Sentinel-2a/b, Landsat 7 ETM+ and Landsat 8 OLI optical imagery across regions of complex terrain.</p><p>Confounding Antarctic Ice Sheet-wide trends of increased glacial recession and mass loss over the long-term satellite era, we detect glaciological advance along 83% of the ice shelves fringing the eastern Antarctic Peninsula between 2009 and 2019. With the exception of SCAR Inlet, where the advance of its terminus position is attributable to long-lasting ice dynamical processes following the disintegration of Larsen B, this phenomenon lies in close agreement with recent observations of unchanged or arrested rates of ice flow and thinning along the coastline. Global climate reanalysis and satellite passive-microwave records reveal that this spatially homogenous advance can be attributed to an enhanced buttressing effect imparted on the eastern Antarctic Peninsula’s ice shelves, governed primarily by regional-scale increases in the delivery and concentration of sea ice proximal to the coastline.</p>

scholarly journals Response of the Antarctic Circumpolar Current to Atmospheric Variability

2008 ◽  
Vol 21 (12) ◽  
pp. 3020-3039 ◽  
Author(s):  
J. B. Sallée ◽  
K. Speer ◽  
R. Morrow
Keyword(s):  
Sea Level ◽  
Southern Hemisphere ◽  
Antarctic Circumpolar Current ◽  
Southern Oscillation ◽  
Atmospheric Forcing ◽  
Atmospheric Variability ◽  
Central Pacific ◽  
Geographical Regions ◽  
Circumpolar Current ◽  
The Antarctic

Abstract Historical hydrographic profiles, combined with recent Argo profiles, are used to obtain an estimate of the mean geostrophic circulation in the Southern Ocean. Thirteen years of altimetric sea level anomaly data are then added to reconstruct the time variable sea level, and this new dataset is analyzed to identify and monitor the position of the two main fronts of the Antarctic Circumpolar Current (ACC) during the period 1993–2005. The authors relate their movements to the two main atmospheric climate modes of the Southern Hemisphere: the Southern Annular Mode (SAM) and the El Niño–Southern Oscillation (ENSO). The study finds that although the fronts are steered by the bathymetry, which sets their mean pathway on first order, in flat-bottom areas the fronts are subject to large meandering because of mesoscale activity and atmospheric forcing. While the dominant mode of atmospheric variability in the Southern Hemisphere, SAM, is relatively symmetric, the oceanic response of the fronts is not, showing substantial regional differences. Around the circumpolar belt the fronts vary in latitude, exposing them to different Ekman transport anomalies induced by the SAM. Three typical scenarios occur in response to atmospheric forcing: poleward movement of the frontal structure in the Indian Basin during positive SAM events, an equatorward movement in the central Pacific, and an intensification without substantial meridional movement in the Indo-Pacific basin. The study also shows the geographical regions that are dominated by a SAM or ENSO response at low and high frequencies.

scholarly journals A High-Resolution Anion Profile of an Ice Core From Dolleman Island, Antarctic Peninsula (Abstract)

1988 ◽  
Vol 11 ◽  
pp. 204-205 ◽  
Author(s):  
Robert Mulvaney ◽  
David A. Peel
Keyword(s):  
High Resolution ◽  
Sea Ice ◽  
Antarctic Peninsula ◽  
Ice Core ◽  
Weddell Sea ◽  
Sea Salt ◽  
Sea Ice Extent ◽  
The Core ◽  
The Antarctic ◽  
Annual Flux

In January 1986, a 133 m ice core, with an estimated age at the bottom of 300-350 years, was collected (using an electromechanical drill) on Dolleman Island (70° 35.2′S, 60°55.5′ W; 398 ma.s.l.; 10 m temperature −16.75°C). The site lies on the east coast of the Antarctic Peninsula and has a continental-type climate dominated by perennial sea ice in the Weddell Sea. The core is being analysed for a range of chemical impurities, in order to assess their potential as indicators of past climate. High-resolution (10-15 samples a−1) continuous profiles of the anionic species Cl−1, NO3 − and SO4 2−, together with the cation Na+, have been measured on a section of the core from 26 to 71 m depth. The core has previously been dated between 0 and 32 m depth using the δ18O profile (Peel and others 1988). Lack of δ18O data for the section 32-71 m forced us to seek an alternative method of dating. Biogenic outgassing of sulphurous gases from the ocean and subsequent photochemical oxidation contribute an excess of sulphate over that derived from the marine aerosol. We show that excess sulphate, calculated as (concentrations in Eq. 1−1 and assuming that all measured Na+ is derived from sea salt), is highly seasonal in character, and annual horizons are well preserved over the whole of the core. This enabled us to determine the chronology to 71 m depth, and date the bottom of this section as 1844 ± 5 years. Cl− is derived mainly from sea salt. Its profile in the core is also seasonal in character, with peaks that tend to occur in late summer, reflecting the period of minimum sea-ice extent in the Weddell Sea, and therefore maximum source area for the uptake of sea salt. From instrumental meteorological records, Limbert (1974) showed that there were three extended periods of warm or cold weather in the Antarctic Peninsula between 1903 and 1944. During the two 4 year cold periods, when the summer break-up of sea ice in the Weddell Sea is likely to have been reduced, we found that the annual flux of Cl− to the Dolleman Island snow-pack was lower than the average. Conversely, the 3 year warm period showed a peak in the values of annual flux of Cl−. We therefore propose that Cl− can be used as a palaeoclimatic indicator for sea-ice extent. Extending our chloride data into the latter half of the nineteenth century (before the earliest continuous instrumental records for the Antarctic), we found three distinct peaks in the values of annual flux of Cl−. We suggest that the period 1850-60 was marked by a decrease in Weddell Sea ice extent (due perhaps to a warm period), followed by an extended period of increased sea ice. There were then two periods of much-reduced sea ice during (approximately) 1885-1890 and 1895-1900, with an intervening period of greatly increased ice coverage. These events are in good agreement with the warm and cold periods which Aristarain and others (1986) identified in the deuterium profile from James Ross Island.

scholarly journals Marine pelagic ecosystems: the West Antarctic Peninsula

2006 ◽  
Vol 362 (1477) ◽  
pp. 67-94 ◽  
Author(s):  
Hugh W Ducklow ◽  
Karen Baker ◽  
Douglas G Martinson ◽  
Langdon B Quetin ◽  
Robin M Ross ◽  
...  
Keyword(s):  
Sea Ice ◽  
Antarctic Peninsula ◽  
Marine Ecosystem ◽  
Ocean Dynamics ◽  
The West ◽  
Sea Ice Extent ◽  
The Past ◽  
West Antarctic ◽  
West Antarctic Peninsula ◽  
The Antarctic

The marine ecosystem of the West Antarctic Peninsula (WAP) extends from the Bellingshausen Sea to the northern tip of the peninsula and from the mostly glaciated coast across the continental shelf to the shelf break in the west. The glacially sculpted coastline along the peninsula is highly convoluted and characterized by deep embayments that are often interconnected by channels that facilitate transport of heat and nutrients into the shelf domain. The ecosystem is divided into three subregions, the continental slope, shelf and coastal regions, each with unique ocean dynamics, water mass and biological distributions. The WAP shelf lies within the Antarctic Sea Ice Zone (SIZ) and like other SIZs, the WAP system is very productive, supporting large stocks of marine mammals, birds and the Antarctic krill, Euphausia superba . Ecosystem dynamics is dominated by the seasonal and interannual variation in sea ice extent and retreat. The Antarctic Peninsula is one among the most rapidly warming regions on Earth, having experienced a 2°C increase in the annual mean temperature and a 6°C rise in the mean winter temperature since 1950. Delivery of heat from the Antarctic Circumpolar Current has increased significantly in the past decade, sufficient to drive to a 0.6°C warming of the upper 300 m of shelf water. In the past 50 years and continuing in the twenty-first century, the warm, moist maritime climate of the northern WAP has been migrating south, displacing the once dominant cold, dry continental Antarctic climate and causing multi-level responses in the marine ecosystem. Ecosystem responses to the regional warming include increased heat transport, decreased sea ice extent and duration, local declines in ice-dependent Adélie penguins, increase in ice-tolerant gentoo and chinstrap penguins, alterations in phytoplankton and zooplankton community composition and changes in krill recruitment, abundance and availability to predators. The climate/ecological gradients extending along the WAP and the presence of monitoring systems, field stations and long-term research programmes make the region an invaluable observatory of climate change and marine ecosystem response.

scholarly journals Albedo of the ice-covered Weddell and Bellingshausen Sea

2011 ◽  
Vol 5 (6) ◽  
pp. 3259-3289 ◽  
Author(s):  
A. I. Weiss ◽  
J. C. King ◽  
T. A. Lachlan-Cope ◽  
R. S. Ladkin
Keyword(s):  
Sea Ice ◽  
Antarctic Peninsula ◽  
Surface Albedo ◽  
Weddell Sea ◽  
Ice Age ◽  
Large Variability ◽  
Linear Temperature ◽  
Pack Ice ◽  
Bellingshausen Sea ◽  
The Antarctic

Abstract. This study investigates the surface albedo of the sea ice areas adjacent to the Antarctic Peninsula during the austral summer. Aircraft measurements of the surface albedo which were conducted in the sea ice areas of the Weddell and Bellingshausen Sea show significant differences between these two regions. The averaged surface albedo varied between 0.13 and 0.81. The ice cover of the Bellingshausen Sea consisted mainly of first year ice and the sea surface showed an averaged sea ice albedo of αi = 0.64 ± 0.2 (± standard deviation). The mean sea ice albedo of the pack ice area in the Western Weddell Sea was αi = 0.75 ± 0.05. In the Southern Weddell Sea, where new, young sea ice prevailed, a mean albedo value of αi = 0.38 ± 0.08 was observed. Relatively warm open water and thin, newly formed ice had the lowest albedo values, whereas relatively cold and snow-covered pack ice had the highest albedo values. All sea ice areas consist of a mixture of a large variability of different sea ice types. An investigation of commonly used parameterizations of albedo as a function of surface temperature in the Weddell and Bellingshausen Sea ice areas showed that the albedo parameterizations don't work well in particular for areas with new, young ice. We determined typical linear temperature-albedo functions for three sea ice areas adjacent to the Antarctic Peninsula, which are reflecting the differences in the mixture of ice age, thickness and sea ice surface cover.

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