scholarly journals Weddell seal behaviour during an exceptional oceanographic event in the Filchner-Ronne Ice Shelf in 2017

2021 ◽  
pp. 1-13
Author(s):  
Sara Labrousse ◽  
Svenja Ryan ◽  
Fabien Roquet ◽  
Baptiste Picard ◽  
Clive R. McMahon ◽  
...  
Keyword(s):  
Ross Sea ◽  
Weddell Seal ◽  
Weddell Sea ◽  
Ice Shelf ◽  
Antarctic Species ◽  
Weddell Seals ◽  
Warm Deep Water ◽  
Shelf Region ◽  
The Impact ◽  
Oceanographic Conditions

Abstract Rapid and regionally contrasting climate changes have been observed around Antarctica. However, our understanding of the impact of these changes on ecosystems remains limited, and there is an urgent need to better identify habitats of Antarctic species. The Weddell seal (Leptonychotes weddellii) is a circumpolar mesopredator and an indicative species of Antarctic marine communities. It has been extensively studied in the western Ross Sea and East Antarctica, and an understanding of its ecology in the Weddell Sea in the wintertime is emerging. We documented the behavioural response(s) of four Weddell seals from February to June in 2017 in the Filchner-Ronne Ice Shelf region and related these to unusual oceanographic conditions in 2017. Unexpectedly, we found that Weddell seals had the longest foraging effort within the outflow of Ice Shelf Water or at its turbulent boundary. They also foraged on the eastern side of the trough from April to June within the Modified Warm Deep Water and seem to take advantage of the unusual conditions of persistent inflow of warm waters through the winter. Linking animal behavioural responses to oceanographic conditions is informative for quantifying rarely recorded events and provides great insight into how predators may respond to changing conditions.

Adjustment of anisakid nematode life cycles to the high Antarctic food web as shown by Contracaecum radiatum and C. osculatum in the Weddell Sea

1992 ◽  
Vol 4 (2) ◽  
pp. 171-178 ◽  
Author(s):  
Heinz Klöser ◽  
Joachim Plötz ◽  
Harry Palm ◽  
Annette Bartsch ◽  
Gerd Hubold
Keyword(s):  
Food Web ◽  
Fish Species ◽  
Nematode Species ◽  
Weddell Seal ◽  
Life Cycles ◽  
Weddell Sea ◽  
Weddell Seals ◽  
Third Stage ◽  
Benthic Food ◽  
Short Type

The infestation of Weddell seals and several fish species by the anisakid nematodes Contracaecum osculatum and C. radiatum was compared. Nematode numbers in Weddell seal stomachs ranged from 30 560 to 122 640. Third stage larvae from seals and fish were separated into a short and a long type. The short type was related to C. radiatum and the long type to C. osculatum. The short type was more abundant in pelagic fish species, whereas the long type prevailed in benthic fish species. Fish-feeding channichthyids Cryodraco antarcticus and Chionodraco myersi seemed to play an important role as paratenic hosts for the third stage larvae of both Contracaecum species. Different advantageous and detrimental features of a benthic versus a pelagic life cycle under high Antarctic ecological conditions are discussed. Varying abundance of the two nematode species in hosts may be controlled by differences in their life cycles, which follow either a pelagic or a benthic food web. Crucial importance is thus given to the local availability of pelagic versus benthic food resources for Weddell seals.

scholarly journals Reducing error and increasing reliability of wildlife counts from citizen science surveys: counting Weddell Seals in the Ross Sea from satellite images

2020 ◽  
Author(s):  
Leo A. Salas ◽  
Michelle LaRue ◽  
Nadav Nur ◽  
David G. Ainley ◽  
Sharon E. Stammerjohn ◽  
...  
Keyword(s):  
Citizen Science ◽  
Satellite Images ◽  
Ross Sea ◽  
Spatial Scales ◽  
Sampling Bias ◽  
Weddell Seal ◽  
Time Of Day ◽  
Weddell Seals ◽  
Novel Approach ◽  
High Resolution Satellite Images

ABSTRACTCitizen science programs can be effective at collecting information at large temporal and spatial scales. However, sampling bias is a concern in citizen science datasets and can lead to unreliable estimates. We address this issue with a novel approach in a first-of-its-kind citizen science survey of Weddell seals for the entire coast of Antarctica. Our citizen scientists inspected very high-resolution satellite images to tag any presumptive seals hauled out on the fast ice during the pupping period. To assess and reduce the error in counts in term of bias and other factors, we ranked surveyors on how well they agreed with each other in tagging a particular feature (presumptive seal), and then ranked these features based on the ranking of surveyors placing tags on them. We assumed that features with higher rankings, as determined by “the crowd wisdom,” were likely to be seals. By comparing citizen science feature ranks with an expert’s determination, we found that non-seal features were often highly ranked. Conversely, some seals were ranked low or not tagged at all. Ranking surveyors relative to their peers was not a reliable means to filter out erroneous or missed tags; therefore, we developed an effective correction factor for both sources of error by comparing surveyors’ tags to those by the expert. Furthermore, counts may underestimate true abundance due to seals not being present on the ice when the image was taken. Based on available on-the-ground haul-out location counts in Erebus Bay, the Ross Sea, we were able to correct for the proportion of seals not detected through satellite images after accounting for year, time-of-day, location (islet vs. mainland locations), and satellite sensor effects. We show that a prospective model performed well at estimating seal abundances at appropriate spatial scales, providing a suitable methodology for continent-wide Weddell Seal population estimates.

Polynoid polychaetes living in the gut of irregular sea urchins: a first case of inquilinism in the Southern Ocean

2011 ◽  
Vol 23 (2) ◽  
pp. 144-151 ◽  
Author(s):  
Stefano Schiaparelli ◽  
Maria Chiara Alvaro ◽  
Ruth Barnich
Keyword(s):  
Sea Urchin ◽  
Ross Sea ◽  
Sea Urchins ◽  
Weddell Sea ◽  
The Other ◽  
Antarctic Species ◽  
Host Switch ◽  
First Case ◽  
Oral Surface ◽  
The Antarctic

AbstractMany different polychaete-echinoderm relationships have been described, from tropical to polar environments. Most of these associations have been generally defined as ‘commensal’, with polychaetes guests usually found on the oral surface of their hosts or, in a very few cases, even inside the host's body. Here we present an inquilinistic association involving two Antarctic species, the polychaete Gorekia crassicirris (Willey, 1902) (Polynoidae) and the irregular sea urchin Abatus nimrodi (Koheler, 1911) (Schizasteridae) found in the Ross Sea. This record is only the second worldwide for this kind of association, after that of the polychaete Benthoscolex cubanus which lives in the gut of the spatangoid Archeopneustes hystrix in Caribbean waters. Gorekia crassicirris seems to be a polyxenous species as it was also observed on another schizasterid, Brachysternaster chescheri Larrain, 1985 in the Weddell Sea. Considering that A. nimrodi is absent from that area and that the two sea urchin species have a disjoint distribution, it is possible that a ‘host-switch’ phenomenon occurred at some stage. We review the available literature to compare the Antarctic pairing with the other known examples of similar associations.

scholarly journals ACCURACY ASSESSMENT OF RECENT GLOBAL OCEAN TIDE MODELS AROUND ANTARCTICA

2017 ◽  
Vol XLII-2/W7 ◽  
pp. 1521-1528 ◽  
Author(s):  
J. Lei ◽  
F. Li ◽  
S. Zhang ◽  
H. Ke ◽  
Q. Zhang ◽  
...  
Keyword(s):  
Accuracy Assessment ◽  
Weddell Sea ◽  
Global Ocean ◽  
Ocean Tide ◽  
Polar Regions ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Ross Ice Shelf ◽  
Shelf Region ◽  
Ocean Tide Models

Due to the coverage limitation of T/P-series altimeters, the lack of bathymetric data under large ice shelves, and the inaccurate definitions of coastlines and grounding lines, the accuracy of ocean tide models around Antarctica is poorer than those in deep oceans. Using tidal measurements from tide gauges, gravimetric data and GPS records, the accuracy of seven state-of-the-art global ocean tide models (DTU10, EOT11a, GOT4.8, FES2012, FES2014, HAMTIDE12, TPXO8) is assessed, as well as the most widely-used conventional model FES2004. Four regions (Antarctic Peninsula region, Amery ice shelf region, Filchner-Ronne ice shelf region and Ross ice shelf region) are separately reported. The standard deviations of eight main constituents between the selected models are large in polar regions, especially under the big ice shelves, suggesting that the uncertainty in these regions remain large. Comparisons with in situ tidal measurements show that the most accurate model is TPXO8, and all models show worst performance in Weddell sea and Filchner-Ronne ice shelf regions. The accuracy of tidal predictions around Antarctica is gradually improving.

scholarly journals An Analysis of Low-Level Jets in the Greater Ross Ice Shelf Region Based on Numerical Simulations

2008 ◽  
Vol 136 (11) ◽  
pp. 4188-4205 ◽  
Author(s):  
Mark W. Seefeldt ◽  
John J. Cassano
Keyword(s):  
Wind Speed ◽  
Ross Sea ◽  
Ice Shelf ◽  
Self Organizing Maps ◽  
Low Level ◽  
Ross Ice Shelf ◽  
The North ◽  
Low Level Jets ◽  
Shelf Region ◽  
Strong Seasonality

Abstract An analysis of the presence and location of low-level jets (LLJs) across the Ross Ice Shelf region in Antarctica is presented based on the analysis of archived output from the real-time Antarctic Mesoscale Prediction System (AMPS). The method of self-organizing maps (SOMs) is used to objectively identify different patterns in column-averaged wind speed (over the approximately lowest 1200 m of the atmosphere) as an identifier to the location of LLJs. The results indicate three primary LLJs in the region. The largest and most dominant LLJ is along the Transantarctic Mountains by the Siple Coast and the southern end of the Ross Ice Shelf. The second LLJ extends from the base of Byrd Glacier and curves to the north passing by the eastern extremes of Ross Island. The third LLJ extends from the base of Reeves Glacier and curves to the north across the western Ross Sea. A strong seasonality is observed in the frequency and intensity of the LLJs with the highest values for wind speed and the size of the LLJ at a maximum during the winter and spring months.

scholarly journals Modeling the Influence of the Weddell Polynya on the Filchner–Ronne Ice Shelf Cavity

2019 ◽  
Vol 32 (16) ◽  
pp. 5289-5303 ◽  
Author(s):  
Kaitlin A. Naughten ◽  
Adrian Jenkins ◽  
Paul R. Holland ◽  
Ruth I. Mugford ◽  
Keith W. Nicholls ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Deep Convection ◽  
Ocean Model ◽  
Shelf Break ◽  
Weddell Sea ◽  
Ice Shelf ◽  
Warm Deep Water ◽  
Regional Ocean Model ◽  
Ocean Models ◽  
Basal Melting

ABSTRACT Open-ocean polynyas in the Weddell Sea of Antarctica are the product of deep convection, which transports Warm Deep Water (WDW) to the surface and melts sea ice or prevents its formation. These polynyas occur only rarely in the observational record but are a near-permanent feature of many climate and ocean simulations. A question not previously considered is the degree to which the Weddell polynya affects the nearby Filchner–Ronne Ice Shelf (FRIS) cavity. Here we assess these effects using regional ocean model simulations of the Weddell Sea and FRIS, where deep convection is imposed with varying area, location, and duration. In these simulations, the idealized Weddell polynyas consistently cause an increase in WDW transport onto the continental shelf as a result of density changes above the shelf break. This leads to saltier, denser source waters for the FRIS cavity, which then experiences stronger circulation and increased ice shelf basal melting. It takes approximately 14 years for melt rates to return to normal after the deep convection ceases. Weddell polynyas similar to those seen in observations have a modest impact on FRIS melt rates, which is within the range of simulated interannual variability. However, polynyas that are larger or closer to the shelf break, such as those seen in many ocean models, trigger a stronger response. These results suggest that ocean models with excessive Weddell Sea convection may not be suitable boundary conditions for regional models of the Antarctic continental shelf and ice shelf cavities.

scholarly journals Abruptly attenuated carbon sequestration with Weddell Sea dense waters towards the end of the 21st century

2021 ◽  
Author(s):  
Cara Nissen ◽  
Ralph Timmermann ◽  
Mario Hoppema ◽  
Judith Hauck
Keyword(s):  
Carbon Sequestration ◽  
Deep Ocean ◽  
Weddell Sea ◽  
Carbon Accumulation ◽  
Ice Shelf ◽  
Warm Deep Water ◽  
High Emission ◽  
Ocean Carbon ◽  
High Emission Scenario ◽  
Model Setup

Abstract Antarctic Bottom Water formation, such as in the Weddell Sea, is an efficient vector for carbon sequestration on time scales of centuries. Possible changes in carbon sequestration under changing environmental conditions are unquantified to date, mainly due to difficulties in simulating the relevant processes on high-latitude continental shelves. Using a model setup including both ice-shelf cavities and oceanic carbon cycling, we demonstrate that by 2100, deep-ocean carbon accumulation in the southern Weddell Sea is abruptly attenuated to only 40% of the rate in the 1990s in a high-emission scenario, while still being 4-fold higher in the 2080s. Assessing deep-ocean carbon budgets and water mass transformations, we attribute this decline to an increased presence of Warm Deep Water on the southern Weddell Sea continental shelf, a 16% reduction in sea-ice formation, and a 79% increase in ice-shelf basal melt. Altogether, these changes lower the density and volume of newly formed bottom waters and reduce the associated carbon transport to the abyss.

scholarly journals The role of tides in ocean--ice-shelf interactions in the southwestern Weddell Sea

2020 ◽  
Author(s):  
Ute Hausmann ◽  
Jean-Baptiste Sallée ◽  
Nicolas Jourdain ◽  
Pierre Mathiot ◽  
Clement Rousset ◽  
...  
Keyword(s):  
Sea Ice ◽  
Freezing Point ◽  
Open Ocean ◽  
Weddell Sea ◽  
Ocean Tides ◽  
Ice Shelf ◽  
Large Variability ◽  
Continental Shelves ◽  
The Impact ◽  
Ocean Boundary

<p>A novel regional ocean-sea-ice model configuration is designed to investigate the mechanisms of ocean–ice-shelf-melt interactions in the Weddell Sea. It features explicit resolution of the cavities of eastern Weddell, Larsen and Filchner-Ronne ice-shelves (FRIS, at 1.5-2.5 km horizontal resolution), as well as of the adjacent continental shelves (~2.5 km) and deep open-ocean gyre (at 2.5-4 km), in presence of interannually-varying atmospheric and ocean boundary forcing as well as explicit ocean tides. Simulated circulation, water mass and ice-shelf melt properties compare overall well with available open-ocean and cavity observations, and simulated Weddell ice-shelf melting reveals large variability on tidal, seasonal and year-to-year timescales. The presence of ocean tides, investigated explicitly, is revealed to result in a systematic time-average enhancement of both the production of ice-shelf meltwater as well as its refreezing on ascending branches of especially the FRIS cavity circulation. This tide-driven enhancement of the melt-induced FRIS cavity circulation acts to increase net ice-shelf melting (by 50%, ~50 Gt/yr) and the meltwater export by the FRIS outflow, and modulates their seasonal and lower frequency variability. The tidal impact on ice-shelf melting is consistent with being primarily driven mechanically through enhanced kinetic energy of the time-varying flow in contact with the ice drafts. The dynamically-driven tide-induced melting is thereby to almost 90% compensated by cooling through meltwater produced, but not quickly exported from regions of melting in the Weddell cold-cavity regime. Ocean boundary layer thermal adjustment underneath ice drafts, minimizing departures from the in-situ freezing point, thus substantially dampens the impact of tides on Weddell ocean–ice-shelf interactions. Simulations furthermore suggest attendant changes on the open-ocean continental shelves, characterized by overall freshening and modest year-round sea-ice thickening, as well as a marked freshening of newly-formed bottom waters in the southwestern Weddell Sea.</p>

scholarly journals Phylogenetic relationship within Cumacea (Crustacea: Peracarida) and genetic variability of two Antarctic species of the family Leuconidae

2020 ◽  
Vol 84 (4) ◽  
pp. 385-392
Author(s):  
Peter Rehm ◽  
Sven Thatje ◽  
Florian Leese ◽  
Christoph Held
Keyword(s):  
Genetic Variability ◽  
16S Rdna ◽  
Family Relationships ◽  
Ross Sea ◽  
Extended Period ◽  
Bimodal Distribution ◽  
Genetic Distances ◽  
Weddell Sea ◽  
Antarctic Species ◽  
Phylogenetic Hypotheses

Phylogenetic hypotheses for the peracarid order Cumacea are scarce and have not provided a solution to the full extent. In the present study, a fragment of the mitochondrial 16S rDNA was used to erect a phylogenetic hypothesis for three cumacean families, Diastylidae, Bodotriidae and Leuconidae, along with intra-family relationships of the latter. The Cumacea resolved monophyletic with tanaids and isopods as outgroup taxa. The Diastylidae were the only family with good support for monophyly. The genus Leucon resolved paraphyletic, whereas the subgenus Crymoleucon was monophyletic. Furthermore, the genetic structure was analysed for two leuconid species, Leucon antarcticus Zimmer, 1907 and L. intermedius Mühlenhardt-Siegel, 1996, from the Weddell Sea and the Ross Sea. The two species showed different patterns of intraspecific genetic variability. In contrast to L. intermedius, a bimodal distribution of pairwise genetic distances was observed for L. antarcticus, which is correlated with geographical and depth distributions between the Ross Sea and the Weddell Sea. Although a clear evaluation of cryptic speciation in these species requires additional work on more specimens from more geographic regions and broader depth ranges, differences shown in the sequences of 16S rDNA can only be explained by genetic separation of populations between the Weddell Sea and the Ross Sea for an extended period of time.

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