On the factors controlling phytoplankton ice edge blooms in the marginal ice zone of the northwestern Weddell Sea during sea ice retreat 1988

AbstractThe ocean response to wintertime sea-ice retreat is investigated in the coupled climate model HiGEM. We focus on the marginal ice zone and adjacent waters of the Nordic Seas, where the air-sea temperature difference can be large during periods of off-ice winds promoting high heat flux events. Both control and transient climate model ensembles are examined, which allows us to isolate the ocean response due to sea-ice retreat from the response due to climate change. As the wintertime sea-ice edge retreats towards the Greenland coastline, it exposes waters that were previously covered by ice which enhances turbulent heat loss and mechanical mixing, leading to a greater loss of buoyancy and deeper vertical mixing in this location. However, under global warming, the buoyancy loss is inhibited as the atmosphere warms more rapidly than the ocean which reduces the air-sea temperature difference. This occurs most prominently further away from the retreating ice edge, over the Greenland Sea gyre. Over the gyre the upper ocean also warms significantly, resulting in a more stratified water column and, as a consequence, a reduction in the depth of convective mixing. In contrast, closer to the coast the effect of global warming is overshadowed by the effect of the sea-ice retreat, leading to significant changes in ocean temperature and salinity in the vicinity of the marginal ice zone.

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On the freshening of the northwestern Weddell Sea continental shelf

Ocean Science ◽

10.5194/os-7-305-2011 ◽

2011 ◽

Vol 7 (3) ◽

pp. 305-316 ◽

Cited By ~ 50

Author(s):

H. H. Hellmer ◽

O. Huhn ◽

D. Gomis ◽

R. Timmermann

Keyword(s):

Sea Ice ◽

Continental Shelf ◽

Weddell Sea ◽

Central Basin ◽

Thermal Front ◽

Late 20Th Century ◽

Ice Shelves ◽

Ice Retreat ◽

Reduced Salt ◽

Sea Ice Retreat

Abstract. We analyzed hydrographic data from the northwestern Weddell Sea continental shelf of the three austral winters 1989, 1997, and 2006 and two summers following the last winter cruise. During summer a thermal front exists at ~64° S separating cold southern waters from warm northern waters that have similar characteristics as the deep waters of the central basin of the Bransfield Strait. In winter, the whole continental shelf exhibits southern characteristics with high Neon (Ne) concentrations, indicating a significant input of glacial melt water. The comparison of the winter data from the shallow shelf off the tip of the Antarctic Peninsula, spanning a period of 17 yr, shows a salinity decrease of 0.09 for the whole water column, which has a residence time of <1 yr. We interpret this freshening as being caused by a combination of reduced salt input due to a southward sea ice retreat and higher precipitation during the late 20th century on the western Weddell Sea continental shelf. However, less salinification might also result from a delicate interplay between enhanced salt input due to sea ice formation in coastal areas formerly occupied by Larsen A and B ice shelves and increased Larsen C ice loss.

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The impact of wintertime sea-ice retreat on convection in the Nordic Seas

10.5194/egusphere-egu2020-462 ◽

2020 ◽

Author(s):

Yue Wu ◽

David Stevens ◽

Ian Renfrew ◽

Xiaoming Zhai

Keyword(s):

Sea Ice ◽

Temperature Difference ◽

North Atlantic ◽

Nordic Seas ◽

Convective Mixing ◽

The North ◽

Ice Retreat ◽

The North Atlantic ◽

Ice Edge ◽

Sea Ice Retreat

<p>The Nordic Seas have a significant impact on global climate due to their role in providing dense overflows to the North Atlantic Ocean.&#160;However,&#160;the dramatic loss of sea ice in recent decades is creating a new atmosphere-ice-ocean environment where large swathes of the ocean that were previously ice-covered are now exposed to the atmosphere. Despite the largest sea-ice loss occurring in summer and autumn, the sea-ice loss in winter and spring is arguably more important for the climate system. Atmosphere-ocean coupling is the most intense in the extended winter, when convective mixing leads to water-mass modification processes, impacting the densest waters of the Atlantic Meridional Overturning Circulation. Here we focus on the marginal-ice-zone of the Nordic Seas where the air-sea temperature difference is large, promoting high heat flux events during periods of off-ice winds. We use both transient and control simulations of the coupled climate model HiGEM, which allows us to isolate the climate change response from the sea-ice retreat response. We find that wintertime sea-ice retreat leads to remarkable changes in ocean surface heat exchanges and wind energy input. As the sea ice edge retreats towards the Greenland coastline, there is a band of exposed ocean which was previously covered by ice. This exposure allows enhanced mechanical mixing by the wind and a greater loss of buoyancy from the ocean leading to deeper vertical mixing in the upper ocean. Sensible and latent heat fluxes from the ocean to the atmosphere provide the greatest loss of buoyancy. However, climate warming inhibits this process as the atmosphere warms more rapidly than the ocean which reduces the sea-air temperature difference. Further away from the retreating ice edge, toward the centre of the Greenland Sea, the upper ocean warms, resulting in a more stratified water column. As a consequence, the depth of convective mixing reduces over the deep ocean and increases over shallower regions close to the coast. This leads to changes in the formation and properties of some of the water masses that enter the North Atlantic and thus may modify the ocean circulation in the subpolar seas in response to sea-ice decline.&#160;</p>

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Climate control of sea-ice edge phytoplankton blooms in the Hudson Bay system

Elem Sci Anth ◽

10.1525/elementa.039 ◽

2020 ◽

Vol 8 (1) ◽

Author(s):

Lucas Barbedo ◽

Simon Bélanger ◽

Jean-Éric Tremblay

Keyword(s):

Sea Ice ◽

Primary Productivity ◽

Marine Ecosystem ◽

Spatiotemporal Variability ◽

Climate Indices ◽

Hudson Bay ◽

The North ◽

Ice Retreat ◽

Ice Edge ◽

Sea Ice Retreat

The Hudson Bay System (HBS), the world’s largest inland sea, has experienced disproportionate atmospheric warming and sea-ice decline relative to the whole Arctic Ocean during the last few decades. The establishment of almost continuous positive atmospheric air temperature anomalies since the late 1990s impacted its primary productivity and, consequently, the marine ecosystem. Here, four decades of archived satellite ocean color were analyzed together with sea-ice and climatic conditions to better understand the response of the HBS to climate forcing concerning phytoplankton dynamics. Using satellite-derived chlorophyll-a concentration [Chla], we examined the spatiotemporal variability of phytoplankton concentration with a focus on its phenology throughout the marginal ice zone. In recent years, phytoplankton phenology was dominated by two peaks of [Chla] during the ice-free period. The first peak occurs during the spring-to-summer transition and the second one happens in the fall, contrasting with the single bloom observed earlier (1978–1983). The ice-edge bloom, that is, the peak in [Chla] immediately found after the sea-ice retreat, showed substantial spatial and interannual variability. During the spring-to-summer transition, early sea-ice retreat resulted in ice-edge bloom intensification. In the northwest polynya, a marine wildlife hot spot, the correlation between climate indices, that is, the North Atlantic Oscillation and Arctic Oscillation (NAO/AO), and [Chla] indicated that the bloom responds to large-scale atmospheric circulation patterns in the North Hemisphere. The intensification of westerly winds caused by the strong polar vortex during positive NAO/AO phases favors the formation of the polynya, where ice production and export, brine rejection, and nutrient replenishment are more efficient. As a result, the winter climate preconditions the upper layer of the HBS for the subsequent development of ice-edge blooms. In the context of a decline in the NAO/AO strength related to Arctic warming, primary productivity is likely to decrease in the HBS and the northwest polynya in particular.

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Transient increase in Arctic deep-water formation and ocean circulation under sea-ice retreat

Journal of Climate ◽

10.1175/jcli-d-21-0152.1 ◽

2021 ◽

pp. 1

Author(s):

Anaïs Bretones ◽

Kerim H. Nisancioglu ◽

Mari F. Jensen ◽

Ailin Brakstad ◽

Shuting Yang

Keyword(s):

Sea Ice ◽

Meridional Overturning Circulation ◽

The Arctic ◽

Deep Water Formation ◽

Water Formation ◽

Ice Retreat ◽

Meridional Overturning ◽

Ice Edge ◽

Sea Ice Edge ◽

Sea Ice Retreat

AbstractWhile a rapid sea-ice retreat in the Arctic has become ubiquitous, the potential weakening of the Atlantic Meridional Overturning Circulation (AMOC) in response to global warming is still under debate. As deep mixing occurs in the open-ocean close to the sea-ice edge, the strength and vertical extent of the AMOC is likely to respond to ongoing and future sea-ice retreat. Here, we investigate the link between changes in Arctic sea-ice cover and AMOC strength in a long simulation with the EC-Earth-PISM climate model under the emission scenario RCP8.5. The extended duration of the experiment (years 1850-2300) captures the disappearance of summer sea ice in 2060 and the removal of winter sea ice in 2165. By introducing a new metric, the Arctic Meridional Overturning Circulation (ArMOC), we document changes beyond the Greenland-Scotland Ridge and into the central Arctic. We find an ArMOC strengthening as the areas of deep mixing move north, following the retreating winter sea-ice edge into the Nansen Basin. At the same time, mixing in the Labrador and Greenland Seas reduces and the AMOC weakens. As the winter sea-ice edge retreats further into the regions with high surface freshwater content in the central Arctic Basin, the mixing becomes shallower and the ArMOC weakens. Our results suggest that the location of deep-water formation plays a decisive role in the structure and strength of the ArMOC; however, the intermittent strengthening of the ArMOC and convection north of the Greenland-Scotland Ridge cannot compensate for the progressive weakening of the AMOC.

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Variability in spring phytoplankton blooms associated with ice retreat timing in the Pacific Arctic from 2003–2019

PLoS ONE ◽

10.1371/journal.pone.0261418 ◽

2021 ◽

Vol 16 (12) ◽

pp. e0261418

Author(s):

Hisatomo Waga ◽

Hajo Eicken ◽

Toru Hirawake ◽

Yasushi Fukamachi

Keyword(s):

Sea Ice ◽

Phytoplankton Biomass ◽

Phytoplankton Bloom ◽

Chukchi Sea ◽

Gaussian Function ◽

Phytoplankton Blooms ◽

The Pacific ◽

Marginal Ice Zone ◽

Ice Retreat ◽

Sea Ice Retreat

The Arctic is experiencing rapid changes in sea-ice seasonality and extent, with significant consequences for primary production. With the importance of accurate monitoring of spring phytoplankton dynamics in a changing Arctic, this study further examines the previously established critical relationship between spring phytoplankton bloom types and timing of the sea-ice retreat for broader temporal and spatial coverages, with a particular focus on the Pacific Arctic for 2003–2019. To this end, time-series of satellite-retrieved phytoplankton biomass were modeled using a parametric Gaussian function, as an effective approach to capture the development and decay of phytoplankton blooms. Our sensitivity analysis demonstrated accurate estimates of timing and presence/absence of peaks in phytoplankton biomass even with some missing values, suggesting the parametric Gaussian function is a powerful tool for capturing the development and decay of phytoplankton blooms. Based on the timing and presence/absence of a peak in phytoplankton biomass and following the classification developed by the previous exploratory work, spring bloom types are classified into three groups (under-ice blooms, probable under-ice blooms, and marginal ice zone blooms). Our results showed that the proportion of under-ice blooms was higher in the Chukchi Sea than in the Bering Sea. The probable under-ice blooms registered as the dominant bloom types in a wide area of the Pacific Arctic, whereas the marginal ice zone bloom was a relatively minor bloom type across the Pacific Arctic. Associated with a shift of sea-ice retreat timing toward earlier dates, we confirmed previous findings from the Chukchi Sea of recent shifts in phytoplankton bloom types from under-ice blooms to marginal ice zone blooms and demonstrated that this pattern holds for the broader Pacific Arctic sector for the time period 2003–2019. Overall, the present study provided additional evidence of the changing sea-ice retreat timing that can drive variations in phytoplankton bloom dynamics, which contributes to addressing the detection and consistent monitoring of the biophysical responses to the changing environments in the Pacific Arctic.

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Moisture transport and Antarctic sea ice: austral spring 2016 event

Earth System Dynamics ◽

10.5194/esd-9-939-2018 ◽

2018 ◽

Vol 9 (3) ◽

pp. 939-954 ◽

Cited By ~ 9

Author(s):

Monica Ionita ◽

Patrick Scholz ◽

Klaus Grosfeld ◽

Renate Treffeisen

Keyword(s):

Indian Ocean ◽

Sea Ice ◽

Ross Sea ◽

Weddell Sea ◽

Antarctic Region ◽

Austral Spring ◽

Ice Retreat ◽

The Indian Ocean ◽

Sea Ice Retreat ◽

The Antarctic

Abstract. In austral spring 2016 the Antarctic region experienced anomalous sea ice retreat in all sectors, with sea ice extent in October and November 2016 being the lowest in the Southern Hemisphere over the observational period (1979–present). The extreme sea ice retreat was accompanied by widespread warming along the coastal areas as well as in the interior of the Antarctic continent. This exceptional event occurred along with a strong negative phase of the Southern Annular Mode (SAM) and the moistest and warmest spring on record, over large areas covering the Indian Ocean, the Ross Sea and the Weddell Sea. In October 2016, the positive anomalies of the totally integrated water vapor (IWV) and 2 m air temperature (T2m) over the Indian Ocean, western Pacific, Bellingshausen Sea and southern part of Ross Sea were unprecedented in the last 39 years. In October and November 2016, when the largest magnitude of negative daily sea ice concentration anomalies was observed, repeated episodes of poleward advection of warm and moist air took place. These results suggest the importance of moist and warm air intrusions into the Antarctic region as one of the main contributors to this exceptional sea ice retreat event.

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Moisture transport and Antarctic sea ice: Austral spring 2016 event

10.5194/esd-2017-114 ◽

2017 ◽

Author(s):

Monica Ionita ◽

Patrick Scholz ◽

Klaus Grosfeld ◽

Renate Treffeisen

Keyword(s):

Indian Ocean ◽

Sea Ice ◽

Ross Sea ◽

Weddell Sea ◽

Antarctic Region ◽

Austral Spring ◽

Ice Retreat ◽

The Indian Ocean ◽

Sea Ice Retreat ◽

The Antarctic

Abstract. In austral spring 2016 the Antarctic region experienced anomalous sea ice retreat in all sectors, with sea ice extent in October and November 2016 being the lowest in the Southern Hemisphere over the observational record (1979–present). The extreme sea ice retreat was accompanied by widespread warming along the coastal areas as well as in the interior of the Antarctic continent. This exceptional event occurred along with a strong negative phase of the Southern Annular Mode (SAM) and the wettest and warmest spring on record, over large areas covering the Indian ocean, the Ross Sea and the Weddell Sea. In October 2016, the positive anomalies of the totally integrated water vapor (IWV) and 2 m air temperature (TT) over the Indian Ocean, Western Pacific, Bellingshausen Sea and southern part of Ross Sea were unprecedented in the last 39 years. In October and November 2016, when the lowest daily sea ice concentration anomalies were observed, repeated episodes of poleward advection of warm and moist air took place, with the most intense episode occurring at the end of November 2016. These results suggest the importance of moist and warm air intrusions into the Antarctic region as one of the main contributors to this exceptional sea ice retreat event.

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