Ocean circulation off east Antarctica affects ecosystem structure and sea-ice extent

Nicol, Stephen; Pauly, Tim; Bindoff, Nathaniel L.; Wright, Simon W.; Thiele, Deborah; Hosie, Graham W.; Strutton, Peter G.; Woehler, Eric J.

doi:10.1038/35020053

Cited by 278 publications

(222 citation statements)

References 22 publications

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“…5d). Our results contribute to existing studies investigating the krill life cycle around Antarctica and/or transport mechanisms that support the highest krill biomass in East Antarctica 30 , western Antarctic Peninsula 31 and Scotia Sea regions 16 .…”

Section: Nature Ecology and Evolutionsupporting

confidence: 61%

The winter pack-ice zone provides a sheltered but food-poor habitat for larval Antarctic krill

et al. 2017

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A ntarctic krill Euphausia superba, a key species in Southern Ocean food webs 1 , plays a central role in ecosystem processes and community dynamics of apex predators, and is the target of a commercial fishery 2 . Krill spawn in late spring and their larvae develop during summer, autumn and under the ice in winter to emerge as juveniles in the following spring. The newly spawned eggs sink from the surface to up to 1,000 m depth where they hatch and the developing larvae actively swim upwards to feed in the upper water column 1 . Larval Antarctic krill have low lipid reserves, which are insufficient to support long periods of starvation. Therefore, winter, when primary production is minimal, is assumed to be a critical bottleneck for larval krill development and hence recruitment to the adult population 3,4 . Present hypotheses suggest that high algal biomass in winter sea ice enhances larval krill winter-feeding conditions and growth [5][6][7][8] . This implies that larvae have access to this high algal biomass within the sea ice. However, recent observations 9,10 indicate that the linkage between sea ice and krill recruitment success is not as direct as has been suggested. The timing of ice-edge advance and annual ice-season duration is highly variable, and does not necessarily show a clear link to krill recruitment in the following year ( Supplementary Figs. 1 and 2). Along the Antarctic Peninsula, adult krill have a five to six year population cycle with oscillations in biomass exceeding an order of magnitude 9 . According to bioenergetics models, part of the variability is due to interannual variation in reproductive output 11 as well as autumn blooms that may govern the possible overwinter survival rate of larvae 11,12 . In the Bransfield Strait, three krill winter surveys have shown that krill abundance is an order of magnitude higher than in summer, regardless of concurrent sea-ice conditions 10 A dominant Antarctic ecological paradigm suggests that winter sea ice is generally the main feeding ground for krill larvae. Observations from our winter cruise to the southwest Atlantic sector of the Southern Ocean contradict this view and present the first evidence that the pack-ice zone is a food-poor habitat for larval development. In contrast, the more open marginal ice zone provides a more favourable food environment for high larval krill growth rates. We found that complex under-ice habitats are, however, vital for larval krill when water column productivity is limited by light, by providing structures that offer protection from predators and to collect organic material released from the ice. The larvae feed on this sparse ice-associated food during the day. After sunset, they migrate into the water below the ice (upper 20 m) and drift away from the ice areas where they have previously fed. Model analyses indicate that this behaviour increases both food uptake in a patchy food environment and the likelihood of overwinter transport to areas where feeding conditions are more favourable in spring.

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Section: Nature Ecology and Evolutionsupporting

confidence: 61%

The winter pack-ice zone provides a sheltered but food-poor habitat for larval Antarctic krill

et al. 2017

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“…Changing influences of warm and cold air flows and oceanic temperature anomalies advected by ocean currents result in fluctuations in winter sea-ice extent (Murphy et al, 1995;Nicol et al, 2000Nicol et al, , 2008aNicol et al, , 2008bKwok andComiso, 2002a, 2002b;Comiso et al, 2011;Turner and Marshall, 2011). These latter variations are most marked in the Amundsen Sea and Bellingshausen seas and South Atlantic regions, and are linked to changes in atmospheric circulation in the area of the Amundsen Sea Low (Yuan and Martinson, 2001;Turner and Marshall, 2011).…”

Section: Physical Conditions and Circulation In The Antarcticmentioning

confidence: 95%

“…Ice drift in the Southern Ocean is greatly affected by the eastward flow within the Antarctic Circumpolar Current and a northward dispersal via Ekman transport. Sea ice is also advected by the Ross and Weddell Gyres (Schwegmann et al, 2011), as well as in smaller mesoscale gyres (Nicol et al, 2000;Nicol, 2006). Near the coast, the Antarctic Coastal Current leads to a westward ice drift (Emery et al, 1997).…”

Section: Transport Of Sea Ice In the Arctic And Antarcticmentioning

confidence: 99%

“…Larval and juvenile stages of Antarctic krill (Euphausia superba) use the undersurface of the ice as a refuge from predation and as a source of food (Daly, 1990;Daly and Macaulay, 1991). By incorporating the effects of sea-ice advance/retreat and drift on transport pathways, Thorpe et al (2007) demonstrated that krill interactions with sea ice were important in governing the variability of the circumpolar distribution of Antarctic krill (see also Nicol et al, 2000;Nicol, 2006).…”

Section: Advection Of Sea-ice Biota In the Antarctic And Its Fatementioning

confidence: 99%

“…This freshening is expected to have significant future impacts on the Ross Sea's contribution of deep water and the oceanic thermohaline circulation (Smith et al, 2014a). Elsewhere around the continent south of the Southern Boundary of the Antarctic Circumpolar Current, the oceanographic flows are complex and influenced by local and regional topographic conditions, resulting in a series of meso-scale gyres during summer (Nicol et al, 2000;Nicol, 2006;Williams et al, 2010).…”

Section: Physical Conditions and Circulation In The Antarcticmentioning

confidence: 99%

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Advection in polar and sub-polar environments: Impacts on high latitude marine ecosystems

Hunt

Drinkwater

Arrigo

et al. 2016

Progress in Oceanography

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a b s t r a c tWe compare and contrast the ecological impacts of atmospheric and oceanic circulation patterns on polar and sub-polar marine ecosystems. Circulation patterns differ strikingly between the north and south. Meridional circulation in the north provides connections between the sub-Arctic and Arctic despite the presence of encircling continental landmasses, whereas annular circulation patterns in the south tend to isolate Antarctic surface waters from those in the north. These differences influence fundamental aspects of the polar ecosystems from the amount, thickness and duration of sea ice, to the types of organisms, and the ecology of zooplankton, fish, seabirds and marine mammals. Meridional flows in both the North Pacific and the North Atlantic oceans transport heat, nutrients, and plankton northward into the Chukchi Sea, the Barents Sea, and the seas off the west coast of Greenland. In the North Atlantic, the advected heat warms the waters of the southern Barents Sea and, with advected nutrients and plankton, supports immense biomasses of fish, seabirds and marine mammals. On the Pacific side of the Arctic, cold waters flowing northward across the northern Bering and Chukchi seas during winter and spring limit the ability of boreal fish species to take advantage of high seasonal production there. Southward flow of cold Arctic waters into sub-Arctic regions of the North Atlantic occurs mainly through Fram Strait with less through the Barents Sea and the Canadian Archipelago. In the Pacific, the transport of Arctic waters and plankton southward through Bering Strait is minimal.In the Southern Ocean, the Antarctic Circumpolar Current and its associated fronts are barriers to the southward dispersal of plankton and pelagic fishes from sub-Antarctic waters, with the consequent evolution of Antarctic zooplankton and fish species largely occurring in isolation from those to the north. The Antarctic Circumpolar Current also disperses biota throughout the Southern Ocean, and as a result, the biota tends to be similar within a given broad latitudinal band. South of the Southern Boundary of the ACC, there is a large-scale divergence that brings nutrient-rich water to the surface. This divergence, along with more localized upwelling regions and deep vertical convection in winter, generates elevated nutrient levels throughout the Antarctic at the end of austral winter. However, such elevated nutrient levels do not support elevated phytoplankton productivity through the entire Southern Ocean, as iron concentrations are rapidly removed to limiting levels by spring blooms in deep waters. However, coastal http://dx

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Characteristics of water‐soluble inorganic and organic ions in aerosols over the Southern Ocean and coastal East Antarctica during austral summer

Gao

Qiu

et al. 2013

JGR Atmospheres

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[1] To characterize the concentrations and size distributions of water-soluble organic and inorganic aerosol species, including Na + , non-sea-salt sulfate (nss SO 4 2À ), methane sulfonate (MSA), oxalate, and succinate, over the Southern Ocean (SO) and coastal East Antarctica (CEA), bulk and size-segregated aerosols were collected from 40°S, 100°E to 69°S, 76°E and between 69°S, 76°E and 66°S, 110°E during a cruise from November 2010 to March 2011. Results show that sea salt was the major component of the total aerosol mass, accounting for 72% over the SO and 56% over CEA. The average concentrations of nss SO 4 2À varied from 420 ng m À3 over the SO to 480 ng m À3 over CEA. The concentrations of MSA ranged from 63 to 87 ng m À3 over the SO and from 46 to 170 ng m À3 in CEA. The average concentrations of oxalate were 3.8 ng m À3 over the SO and 2.2 ng m À3 over CEA. The concentrations of formate, acetate, and succinate were lower than those of oxalate. A bimodal size distribution of aerosol mass existed over CEA, peaking at 0.32-0.56 μm and 3.2-5.6 μm. MSA was accumulated in particles of 0.32-0.56 μm over CEA. High chloride depletion was associated with fine-mode particles enriched with nss SO 4 2À , MSA, and oxalate. Higher cation-to-anion and NH 4 + /nss SO 4 2À ratios in aerosols over CEA compared to that over the SO imply the higher neutralization capacity of the marine atmosphere over CEA.

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Ocean circulation off east Antarctica affects ecosystem structure and sea-ice extent

Cited by 278 publications

References 22 publications

The winter pack-ice zone provides a sheltered but food-poor habitat for larval Antarctic krill

The winter pack-ice zone provides a sheltered but food-poor habitat for larval Antarctic krill

Advection in polar and sub-polar environments: Impacts on high latitude marine ecosystems

Characteristics of water‐soluble inorganic and organic ions in aerosols over the Southern Ocean and coastal East Antarctica during austral summer

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