Effects of sea ice cover on the swarming behaviour of Antarctic krill, Euphausia superba

2000 ◽  
Vol 57 (S3) ◽  
pp. 24-30 ◽  
Author(s):  
Andrew S Brierley ◽  
Jonathan L Watkins
Keyword(s):  
Sea Ice ◽  
Antarctic Krill ◽  
Open Water ◽  
Euphausia Superba ◽  
Ice Cover ◽  
Sea Ice Extent ◽  
Neighbour Distance ◽  
Bellingshausen Sea ◽  
Antarctic Krill Euphausia Superba ◽  
Swarming Behaviour

Much of the distribution range of Antarctic krill, Euphausia superba, is covered by permanent or seasonal sea ice. Sea ice extent has been implicated as a major factor affecting reproductive success of krill and krill dispersal, but little is known of the way in which ice cover may influence krill behaviour. This is largely because the under-ice environment is difficult to study. Ship-borne echosounders have, however, detected krill aggregations in midwater in ice-covered regions. We used 120-kHz echograms collected underway during three cruises that crossed ice-covered and adjacent open waters in the Bellingshausen, Weddell, and Scotia seas to compare morphological and next-neighbour characteristics of krill swarms within and without ice cover. No significant differences were detected between the horizontal and vertical extent of swarms or swarm next-neighbour distance in ice-covered or open waters. Distributions of swarm mid-depths did, however, differ significantly between ice-covered and open areas in all three seas, although the direction of difference was not the same in each instance: swarms in the Weddell and Scotia seas were generally shallower under ice than in open water, whereas in the Bellingshausen Sea the opposite prevailed.

scholarly journals A Regional Seasonal Forecast Model of Arctic Minimum Sea Ice Extent: Reflected Solar Radiation vs. Late Winter Coastal Divergence

2021 ◽  
pp. 1
Author(s):  
Rachel Kim ◽  
Bruno Tremblay ◽  
Charles Brunette ◽  
Robert Newton
Keyword(s):  
Solar Radiation ◽  
Sea Ice ◽  
Open Water ◽  
Forecast Model ◽  
Ice Cover ◽  
The Arctic ◽  
Late Winter ◽  
Coupled Models ◽  
Sea Ice Extent ◽  
Predictive Skill

AbstractThinning sea ice cover in the Arctic is associated with larger interannual variability in the minimum Sea Ice Extent (SIE). The current generation of forced or fully coupled models, however, have difficulty predicting SIE anomalies from the long-term trend, highlighting the need to better identify the mechanisms involved in the seasonal evolution of sea ice cover. One such mechanism is Coastal Divergence (CD), a proxy for ice thickness anomalies based on late winter ice motion, quantified using Lagrangian ice tracking. CD gains predictive skill through the positive feedback of surface albedo anomalies, mirrored in Reflected Solar Radiation (RSR), during melt season. Exploring the dynamic and thermodynamic contributions to minimum SIE predictability, RSR, initial SIE (iSIE) and CD are compared as predictors using a regional seasonal sea ice forecast model for July 1, June 1 and May 1 forecast dates for all Arctic peripheral seas. The predictive skill of June RSR anomalies mainly originates from open water fraction at the surface, i.e. June iSIE and June RSR have equal predictive skill for most seas. The finding is supported by the surprising positive correlation found between June Melt Pond Fraction (MPF) and June RSR in all peripheral seas: MPF anomalies indicate presence of ice or open water that is key to creating minimum SIE anomalies. This contradicts models that show correlation between melt onset, MPF and the minimum SIE. A hindcast model shows that for a May 1 forecast, CD anomalies have better predictive skill than RSR anomalies for most peripheral seas.

scholarly journals Sea-ice extent in the Southern Ocean during the Last Glacial Maximum: another approach to the problem

1998 ◽  
Vol 27 ◽  
pp. 302-304 ◽  
Author(s):  
Lloyd H. Burckle ◽  
Richard Mortlock
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Surface Sediments ◽  
Open Water ◽  
Ice Cover ◽  
Polar Front ◽  
Age Dating ◽  
Antarctic Polar Front ◽  
Sea Ice Extent ◽  
Biogenic Opal

Determining past sea-ice distribution is an important goal of paleocean-ographers. Here, we present a possible approach to determining past sea-ice distribution in the Southern Ocean during the Last Glaciol Maximum (LGM). Diatoms are the prin-cipal opal-forming organisms south of the Antarctic Polar Front; their productivity is partly mediated by the presence/absence of sea ice. We reasoned that there should be good coherence between percentage biogenic opal in surface sediments and percentage annual sea-ice cover. This hypothesis was tested by comparing percentage biogenic opal in surface sediments against modern-day sea-ice cover in surface waters directly above each core site. The chronology for each core was determined by various means (biostratigraphy, 14C age dating, and carbonate and opal stratigraphy). With the resulting curve we estimate that yearly concentration of sea ice can be determined to within 30%. Using these data, we estimated percentage sea-ice cover during the LGM for a number of sediment sites (50-66°S) from the Southern Ocean. Core sites now beneath 100% open water witnessed some 25-60% sea ice during the LGM, while core sites presently beneath sea ice during half of the year witnessed more than 75% sea-ice cover during the LGM.

scholarly journals Imprint of Arctic sea ice cover in North-Greenland ice cores

2019 ◽  
Author(s):  
Damiano Della Lunga ◽  
Hörhold Maria ◽  
Birthe Twarloh ◽  
Behrens Melanie ◽  
Dallmayr Remi ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ice Cores ◽  
Open Water ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
Blowing Snow ◽  
Sea Ice Extent ◽  
Arctic Sea ◽  
Frost Flowers ◽  
North Greenland

Abstract. Sea ice is a key component of the climate system, since it modifies the surface albedo, the radiation balance, as well as the exchange of heat, moisture and gases between the ocean and the overlying atmosphere. Hence, the reconstruction of sea ice cover before the instrumental era and the industrial times is crucial to understand the evolution of Arctic climate in the last millennium and better predict its future evolution. However, identifying relevant paleo proxies in climate archives related to sea ice cover is not straightforward. Ice cores from polar regions offer great potential to provide high-resolution records of Arctic sea ice variability from chemical impurities such as Bromine species, which were recently proposed as indicators of sea ice extent, although their variability might be modulated by regional influences. We here use Bromine and Bromine enrichment of two ice cores form North Greenland (B17 & B26) and investigate its potential as proxy to reconstruct sea ice extent over the period 1363–1993 AD. Across the instrumental period, a good correlation is observed with the Baffin Bay and the Greenland Sea for B26 and B17 respectively, with both record showing minima corresponding to known Artic warming events such as the 1420 AD (for B17) and 1920–1940 (Early century warming, B17 & B26), together with a strong decline starting in the late 19th century. We simultaneously derived a chemical classification of sea ice-related contributors of ionic species (i.e. blowing snow, frost flowers, open water) utilizing the depletion of SO42− compare to Ca2+, K+ and Mg2+ characterizing sea ice brines and blowing snow as well the excess of Br− and Cl−, characterizing frost flowers, to elucidate the evolution of the different sources. In both B17 and B26 records we observe a strong contribution of blowing snow in the earliest part of the datasets, gradually declining in recent years in favour of open water sources.

scholarly journals Flexibility in Antarctic krill Euphausia superba decouples diet and recruitment from overwinter sea-ice conditions in the northern Antarctic Peninsula

2020 ◽  
Vol 642 ◽  
pp. 1-19 ◽  
Author(s):  
J Walsh ◽  
CS Reiss ◽  
GM Watters
Keyword(s):  
Sea Ice ◽  
Water Column ◽  
Antarctic Peninsula ◽  
Lipid Content ◽  
Environmental Variables ◽  
Antarctic Krill ◽  
Euphausia Superba ◽  
Ice Cover ◽  
Ice Conditions ◽  
Ice Resources

Winter sea-ice conditions are considered important for Antarctic krill Euphausia superba survival and recruitment, yet few broad-scale longitudinal studies have examined the underlying relationships between winter conditions and krill recruitment. We used data from a 4 yr winter study of krill condition (lipid content), diet (stable isotopes and fatty acids), and length distributions around the northern Antarctic Peninsula to examine relationships among environmental variables (annual sea-ice cover, water column chlorophyll a [chl a], and upper mixed-layer water temperature), the condition and diet of krill, and recruitment success the following year. Diet indicators (lipid content, δ15N, δ13C, and the fatty acid ratios 16:1n-7/18:4n-3 and 18:1n-9/18:1n-7) in post-larvae were consistent among years regardless of sea-ice cover, suggesting that post-larval krill do not rely on sea-ice resources for overwinter survival. Diet indicators in larvae were more variable and suggest that larvae may feed on sea-ice resources when they are available but can still persist in the water column when they are not. Principal component analysis between environmental variables and diet indicators showed that water-column chl a was the only variable that significantly affected diet, regardless of annual changes in sea-ice cover. Extensive winter ice in one year did not translate into successful recruitment the following year. Krill demonstrate a high degree of flexibility with respect to overwinter habitat and diet, and the degree to which sea ice is important during different times of year and at different life stages may be more complex than previously thought.

scholarly journals Foraging behavior of antarctic krill Euphausia superba on sea ice microalgae

1988 ◽  
Vol 44 ◽  
pp. 131-139 ◽  
Author(s):  
JJ Stretch ◽  
PP Hamner ◽  
WM Hamner ◽  
WC Michel ◽  
J Cook ◽  
...  
Keyword(s):  
Sea Ice ◽  
Foraging Behavior ◽  
Antarctic Krill ◽  
Euphausia Superba ◽  
Antarctic Krill Euphausia Superba

Observation on behaviours of Antarctic krill (Euphausia superba) in lighting condition

2012 ◽  
Vol 36 (2) ◽  
pp. 300
Author(s):  
Peng-xiang XU ◽  
Ying-chun LI ◽  
Guo-ping ZHU ◽  
Hui XIA ◽  
Liu-xiong XU
Keyword(s):  
Antarctic Krill ◽  
Euphausia Superba ◽  
Lighting Condition ◽  
Antarctic Krill Euphausia Superba

Observations on moulting in Antarctic Krill (Euphausia superba Dana)

1982 ◽  
Vol 33 (1) ◽  
pp. 71 ◽  
Author(s):  
T Ikeda ◽  
P Dixon
Keyword(s):  
Phaeodactylum Tricornutum ◽  
Antarctic Krill ◽  
Dry Weight ◽  
Euphausia Superba ◽  
Dunaliella Tertiolecta ◽  
Antarctic Ocean ◽  
Fish Food ◽  
Antarctic Waters ◽  
The Antarctic ◽  
Antarctic Krill Euphausia Superba

Live E. superba were transported from Antarctic waters to a tropical laboratory where observations at the temperature of -0.5�C (0 to - 1.0�C), were made of intermoult period of specimens fed a mixture of microalgae (Dunaliella tertiolecta and Phaeodactylum tricornutum) or artificial pet fish food or starved. Mean intermoult period was 26.4-27.1 days for fed specimens and 29.6 days for starved specimens, with no relation to the size of specimens. The moult accounted for a loss of 2.63-4.35% of animal dry weight, which is equivalent to 1.1-1.8% of animal nitrogen or 1.4-2.3% of animal carbon. The contribution of moults to detritus in the Antarctic Ocean was estimated as 0.11 g C m-2 per year.

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