The effect of marginal ice-edge dynamics on production and export in the Southern Ocean along 170°W

Abstract. Sea-ice cover over the Southern Ocean responds to and impacts Southern Ocean dynamics and, thus, mid to high latitude climate in the Southern Hemisphere. In addition, sea-ice cover can significantly modulate the carbon exchange between the atmosphere and the ocean. As climate models are the only tool available to project future climate changes, it is important to assess their performance in simulating past changes. The Last Glacial Maximum (LGM, ∼21,000 years ago) represents an interesting target as it is a relatively well documented period with climatic conditions and a carbon cycle very different from pre-industrial conditions. Here, we study the changes in seasonal Antarctic sea-ice cover as simulated in numerical PMIP3 and LOVECLIM simulations of the LGM, and their relationship with windstress and ocean temperature. Simulations and paleo-proxy records suggest a fairly well constrained glacial winter sea-ice edge at 51.5° S (1 sigma range: 50°–55.5° S). Simulated glacial summer sea-ice cover however differs widely between models, ranging from almost no sea ice to a sea-ice edge reaching 55.5° S. The austral summer multi-model mean sea-ice edge lies at ∼60.5° S (1 sigma range: 57.5°–70.5° S). Given the lack of strong constraints on the summer sea-ice edge based on sea-ice proxy records, we extend our model-data comparison to summer sea-surface temperature. Our analysis suggests that the multi-model mean summer sea ice provides a reasonable, albeit upper end, estimate of the austral summer sea-ice edge allowing us to conclude that the multi-model mean of austral summer and winter sea-ice cover seem to provide good estimates of LGM conditions. Using these best estimates, we find that there was a larger sea-ice seasonality during the LGM compared to the present day.

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Interannual Sea-Ice Variations and Sea-Ice/Atmosphere Interations in the Southern Ocean, 1973–1975

Annals of Glaciology ◽

10.3189/s026030550000286x ◽

1982 ◽

Vol 3 ◽

pp. 249-254 ◽

Cited By ~ 4

Author(s):

Claire L. Parkinson ◽

Donald J. Cavalieri

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Interannual Variability ◽

Sea Level ◽

Spatial Dependence ◽

Spatial Coherence ◽

Yearly Cycle ◽

Small Term ◽

The Mean ◽

Ice Edge

Examination of satellite-derived 1973–75 sea-ice concentrations for the Southern Ocean and comparison with 1 000 mbar temperatures and sea-level pressures reveal considerable Interannual variability in both the ice and atmospheric fields plus strong suggestions of ice/atmosphere interconnections. The mean position of the ice edge undergoes a strong yearly cycle that lags the cycle of the zonally-averaged temperatures by about one month, but the mean ice edge does not contain small-term fluctuations or interannual variability to the same extent as either the temperature or the pressure. Regionally, the ice varies much more noticeably from year-to-year, with the interannual contrasts showing strong spatial dependence in all months and strong spatial coherence in winter. These are illustrated by selected maps of monthly differences in ice concentrations between 1973 and 1974 and between 1974 and 1975. It is shown that the interannual ice differences can, in many cases, be attributed to the Interannual differences in the positioning and intensity of cyclonic and anticyclonic systems.

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Search for the Little Ice Age in Southern Ocean Sea-Ice Records

Annals of Glaciology ◽

10.1017/s0260305500008624 ◽

1990 ◽

Vol 14 ◽

pp. 221-225 ◽

Cited By ~ 17

Author(s):

Claire L. Parkinson

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Little Ice Age ◽

Weddell Sea ◽

Ice Age ◽

Amundsen Sea ◽

Ice Edge ◽

Time Of Year ◽

Sea Ice Edge ◽

Eastern Weddell Sea

Records from the expeditions of Cook, Bellingshausen, Wilkes, and Ross in the late 18th and early 19th centuries have been examined for the information they provide on locations of the Southern Ocean sea-ice edge during the period of the late Little Ice Age in much of the Northern Hemisphere. When these locations are compared with satellite-derived ice edge locations in the mid 1970s, there is a suggestion of particularly heavy ice covers in the eastern Weddell Sea in December 1772, in the Amundsen Sea in March 1839, and perhaps, on the basis of an isolated observation, in a portion of the western Weddell Sea in January 1820. However, overall no strong Little Ice Age signal is found for the sea ice of the Southern Ocean. Many of the observations from the four expeditions indicate sea-ice edge locations that lie within the range of ice edge locations at the same time of year in the mid 1970s, and a few of the observations suggest a less extensive ice cover than in the 1970s.

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Southern Ocean Biogeochemical Argo detect under-ice phytoplankton growth before sea ice retreat

Biogeosciences ◽

10.5194/bg-18-25-2021 ◽

2021 ◽

Vol 18 (1) ◽

pp. 25-38

Author(s):

Mark Hague ◽

Marcello Vichi

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Light Adaptation ◽

Ice Cover ◽

Data Sampling ◽

Argo Data ◽

Ice Melt ◽

Antarctic Sea Ice ◽

Ice Retreat ◽

Ice Edge

Abstract. The seasonality of sea ice in the Southern Ocean has profound effects on the life cycle (phenology) of phytoplankton residing under the ice. The current literature investigating this relationship is primarily based on remote sensing, which often lacks data for half of the year or more. One prominent hypothesis holds that, following ice retreat in spring, buoyant meltwaters enhance available irradiance, triggering a bloom which follows the ice edge. However, an analysis of Biogeochemical Argo (BGC-Argo) data sampling under Antarctic sea ice suggests that this is not necessarily the case. Rather than precipitating rapid accumulation, we show that meltwaters enhance growth in an already highly active phytoplankton population. Blooms observed in the wake of the receding ice edge can then be understood as the emergence of a growth process that started earlier under sea ice. Indeed, we estimate that growth initiation occurs, on average, 4–5 weeks before ice retreat, typically starting in August and September. Novel techniques using on-board data to detect the timing of ice melt were used. Furthermore, such growth is shown to occur under conditions of substantial ice cover (>90 % satellite ice concentration) and deep mixed layers (>100 m), conditions previously thought to be inimical to growth. This led to the development of several box model experiments (with varying vertical depth) in which we sought to investigate the mechanisms responsible for such early growth. The results of these experiments suggest that a combination of higher light transfer (penetration) through sea ice cover and extreme low light adaptation by phytoplankton can account for the observed phenology.

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Mechanisms controlling the temporal variation of the sea ice edge in the Southern Ocean

Journal of Oceanography ◽

10.1007/s10872-007-0060-3 ◽

2007 ◽

Vol 63 (4) ◽

pp. 685-694 ◽

Cited By ~ 5

Author(s):

Noriaki Kimura

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Temporal Variation ◽

Ice Edge ◽

Sea Ice Edge

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Krill fishing activity in the southwest Atlantic

Antarctic Science ◽

10.1017/s0954102091000445 ◽

1991 ◽

Vol 3 (4) ◽

pp. 351-358 ◽

Cited By ~ 40

Author(s):

Inigo Everson ◽

Catherine Goss

Keyword(s):

Southern Ocean ◽

Shelf Zone ◽

Commercial Fishing ◽

Fishing Activity ◽

Southwest Atlantic ◽

Reporting Scheme ◽

Catch Data ◽

Antarctic Marine ◽

Ice Edge ◽

Half Degree

Commercial krill fishing has been undertaken in the Southern Ocean for twenty years. Recently the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) introduced a reporting scheme to summarize catch data from half degree of latitude by one degree of longitude rectangles. These data demonstrate that commercial fishing in the southwest Atlantic is concentrated in the shelf zone. Certain krill predators are also restricted to this area whilst collecting food for their young during the summer. Krill fishing takes place year round, moving northwards in winter as the ice edge advances.

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Interannual Sea-Ice Variations and Sea-Ice/Atmosphere Interations in the Southern Ocean, 1973–1975

Annals of Glaciology ◽

10.1017/s026030550000286x ◽

1982 ◽

Vol 3 ◽

pp. 249-254 ◽

Cited By ~ 12

Author(s):

Claire L. Parkinson ◽

Donald J. Cavalieri

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Interannual Variability ◽

Sea Level ◽

Spatial Dependence ◽

Spatial Coherence ◽

Yearly Cycle ◽

Small Term ◽

The Mean ◽

Ice Edge

Examination of satellite-derived 1973–75 sea-ice concentrations for the Southern Ocean and comparison with 1 000 mbar temperatures and sea-level pressures reveal considerable Interannual variability in both the ice and atmospheric fields plus strong suggestions of ice/atmosphere interconnections. The mean position of the ice edge undergoes a strong yearly cycle that lags the cycle of the zonally-averaged temperatures by about one month, but the mean ice edge does not contain small-term fluctuations or interannual variability to the same extent as either the temperature or the pressure. Regionally, the ice varies much more noticeably from year-to-year, with the interannual contrasts showing strong spatial dependence in all months and strong spatial coherence in winter. These are illustrated by selected maps of monthly differences in ice concentrations between 1973 and 1974 and between 1974 and 1975. It is shown that the interannual ice differences can, in many cases, be attributed to the Interannual differences in the positioning and intensity of cyclonic and anticyclonic systems.

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Importance of Ice Edge Phytoplankton Production in the Southern Ocean

BioScience ◽

10.2307/1310215 ◽

1986 ◽

Vol 36 (4) ◽

pp. 251-257 ◽

Cited By ~ 307

Author(s):

Walker O. Smith, ◽

David M. Nelson

Keyword(s):

Southern Ocean ◽

Phytoplankton Production ◽

Ice Edge

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