scholarly journals A Numerical Investigation of Formation and Variability of Antarctic Bottom Water off Cape Darnley, East Antarctica

2014 ◽  
Vol 44 (11) ◽  
pp. 2921-2937 ◽  
Author(s):  
Yoshihiro Nakayama ◽  
Kay I. Ohshima ◽  
Yoshimasa Matsumura ◽  
Yasushi Fukamachi ◽  
Hiroyasu Hasumi
Keyword(s):  
Sea Ice ◽  
Continental Slope ◽  
Bottom Water ◽  
Heat Budget ◽  
East Antarctica ◽  
Salt Flux ◽  
Ice Formation ◽  
Minor Importance ◽  
Antarctic Bottom Water ◽  
Dense Water

Abstract At several locations around Antarctica, dense water is formed as a result of intense sea ice formation. When this dense water becomes sufficiently denser than the surrounding water, it descends the continental slope and forms Antarctic Bottom Water (AABW). This study presents the AABW formation off the coast of Cape Darnley [Cape Darnley Bottom Water (CDBW)] in East Antarctica, using a nonhydrostatic model. The model is forced for 8 months by a temporally uniform surface salt flux (because of sea ice formation) estimated from Advanced Microwave Scanning Radiometer for Earth Observing System (EOS; AMSR-E) data and a heat budget calculation. The authors reproduce AABW formation and associated periodic downslope flows of dense water. Descending pathways of dense water are largely determined by the topography; most dense water flows into depressions on the continental shelf, advects onto the continental slope, and is steered downslope to greater depths by the canyons. Intense sea ice formation is the most important factor in the formation of AABW off Cape Darnley, and the existence of depressions is of only minor importance for the flux of CDBW. The mechanism responsible for the periodic downslope flow of dense water is further analyzed using an idealized model setup. The period of dense water outflow is regulated primarily by the topographic beta effect.

Antarctic Bottom Water production by intense sea-ice formation in the Cape Darnley polynya

2013 ◽  
Vol 6 (3) ◽  
pp. 235-240 ◽  
Author(s):  
Kay I. Ohshima ◽  
Yasushi Fukamachi ◽  
Guy D. Williams ◽  
Sohey Nihashi ◽  
Fabien Roquet ◽  
...  
Keyword(s):  
Sea Ice ◽  
Bottom Water ◽  
Ice Formation ◽  
Antarctic Bottom Water ◽  
Water Production

Recent recovery of Antarctic Bottom Water formation in the Ross Sea driven by climate anomalies

2021 ◽  
Author(s):  
Alessandro Silvano ◽  
Annie Foppert ◽  
Steve Rintoul ◽  
Paul Holland ◽  
Takeshi Tamura ◽  
...  
Keyword(s):  
Sea Ice ◽  
Continental Shelf ◽  
Bottom Water ◽  
Ross Sea ◽  
Ice Sheet ◽  
Ice Formation ◽  
Depth Range ◽  
Antarctic Bottom Water ◽  
Climate Anomalies ◽  
The Antarctic

<div> <div> <div> <p>Antarctic Bottom Water (AABW) supplies the lower limb of the global overturning circulation, ventilates the abyssal ocean and sequesters heat and carbon on multidecadal to millennial timescales. AABW originates on the Antarctic continental shelf, where strong winter cooling and brine released during sea ice formation produce Dense Shelf Water, which sinks to the deep ocean. The salinity, density and volume of AABW have decreased over the last 50 years, with the most marked changes observed in the Ross Sea. These changes have been attributed to increased melting of the Antarctic Ice Sheet. Here we use in situ observations to document a recovery in the salinity, density and thickness (that is, depth range) of AABW formed in the Ross Sea, with properties in 2018–2019 similar to those observed in the 1990s. The recovery was caused by increased sea ice formation on the continental shelf. Increased sea ice formation was triggered by anomalous wind forcing associated with the unusual combination of positive Southern Annular Mode and extreme El Niño conditions between 2015 and 2018. Our study highlights the sensitivity of AABW formation to remote forcing and shows that climate anomalies can drive episodic increases in local sea ice formation that counter the tendency for increased ice-sheet melt to reduce AABW formation.</p> </div> </div> </div>

scholarly journals Flow of Antarctic Bottom Water from the Vema Channel 

2020 ◽  
Author(s):  
Eugene G Morozov ◽  
Dmitry I. Frey ◽  
Roman Y. Tarakanov
Keyword(s):  
Continental Slope ◽  
Water Flow ◽  
North Atlantic ◽  
Bottom Water ◽  
The Other ◽  
Antarctic Bottom Water ◽  
The North ◽  
The North Atlantic ◽  
Current Flows ◽  
Western Wall

Abstract We analyze measurements of bottom currents and thermohaline properties of water north of the Vema Channel with the goal to find pathway continuations of Antarctic Bottom Water flow from the Vema Channel into the Brazil Basin. The analysis is based on CTD/LADCP casts north of the Vema Channel. The flow in the deep Vema Channel consists of two branches. The deepest current flows along the bottom in the center of the channel and the other branch flows above the western wall of the channel. We found two smaller channels of the northern continuation of the deeper bottom flow. These flows become weak and almost disappear at a latitude of 25°30’S. The upper current flows at a depth of 4100-4200 m along the continental slope. We traced this current up to 24°S over a distance exceeding 250 km. This branch transports bottom water that eventually fills the deep basins of the North Atlantic.

scholarly journals Snow-ice growth: a fresh-water flux inhibiting deep convection in the Weddell Sea, Antarctica

2001 ◽  
Vol 33 ◽  
pp. 45-50 ◽  
Author(s):  
V.I. Lytle ◽  
S.F. Ackley
Keyword(s):  
Sea Ice ◽  
Thermohaline Circulation ◽  
Deep Convection ◽  
Ice Cover ◽  
Snow Accumulation ◽  
Heat Fluxes ◽  
Weddell Sea ◽  
Salt Flux ◽  
Ice Formation ◽  
Atmospheric Conditions

AbstractDuring a field experiment in July 1994, while the R.V. Nathaniel B. Palmer was moored to a drifting ice floe in the Weddell Sea, Antarctica, data were collected on sea-ice and snow characteristics. We report on the evolution of ice which grew in a newly opened lead. As expected with cold atmospheric conditions, congelation ice initially formed in the lead. Subsequent snow accumulation and large ocean heat fluxes resulted in melt at the base of the ice, and enhanced flooding of the snow on the ice surface. This flooded snow subsequently froze, and, 5 days after the lead opened, all the congelation ice had melted and 26 cm of snow ice had formed. We use measured sea-ice and snow salinities, thickness and oxygen isotope values of the newly formed lead ice to calculate the salt flux to the ocean. Although there was a salt flux to the ocean as the ice initially grew, we calculate a small net fresh-wlter input to the upper ocean by the end of the 5 day period. Similar processes of basal melt and surface snow-ice formation also occurred on the surrounding, thicker sea ice. Oceanographic studies in this region of the Weddell Sea have shown that salt rejection by sea-ice formation may enhance the ocean vertical thermohaline circulation and release heat from the deeper ocean to melt the ice cover. This type of deep convection is thought to initiate the Weddell polynya, which was observed only during the 1970s. Our results, which show that an ice cover can form with no salt input to the ocean, provide a mechanism which may help explain the more recent absence of the Weddell polynya.

scholarly journals Creation of a Heat and Salt Flux Dataset Associated with Sea Ice Production and Melting in the Sea of Okhotsk

2012 ◽  
Vol 25 (7) ◽  
pp. 2261-2278 ◽  
Author(s):  
Sohey Nihashi ◽  
Kay I. Ohshima ◽  
Noriaki Kimura
Keyword(s):  
Spatial Distribution ◽  
Sea Ice ◽  
Sea Of Okhotsk ◽  
Heat Budget ◽  
Salt Flux ◽  
The Sea Of Okhotsk ◽  
Ice Melt ◽  
Budget Analysis ◽  
Coastal Polynya ◽  
Ice Production

Abstract Sea ice formation, its transport, and its melting cause the redistribution of heat and salt, which plays an important role in the climate and biogeochemical systems. In the Sea of Okhotsk, a heat and salt flux dataset is created in which such sea ice processes are included, with a spatial resolution of ~12.5 km. The dataset is based on a heat budget analysis using ice concentration, thickness, and drift speed from satellite observations and the ECMWF Interim Re-Analysis (ERA-Interim) data. The salt flux calculation considers both salt supplied to the ocean from sea ice production and freshwater supplied when the ice melts. This dataset will be useful for the validation and boundary conditions of modeling studies. The spatial distribution of the annual fluxes shows a distinct contrast between north and south: significant ocean cooling with salt supply is shown in the northern coastal polynya region, while ocean heating with freshwater supply is shown in the south. This contrast suggests a transport of freshwater and negative heat by ice advection. The annual fluxes also show ocean cooling with freshwater supply in the Kashevarov Bank (KB) region and the central and eastern Sea of Okhotsk, suggesting the effect of warm water advection. In the ice melt season, relatively prominent ice melting is shown in the coastal polynya region, probably due to large solar heating of the upper ocean. This indicates that the polynya works as a “meltwater factory” in spring, contrasting with its role as an “ice factory” in winter. In the coastal polynya region, the spatial distribution of phytoplankton bloom roughly corresponds with the ice melt region.

scholarly journals Brief communication: Impacts of a developing polynya off Commonwealth Bay, East Antarctica, triggered by grounding of iceberg B09B

2016 ◽  
Vol 10 (6) ◽  
pp. 2603-2609 ◽  
Author(s):  
Christopher J. Fogwill ◽  
Erik van Sebille ◽  
Eva A. Cougnon ◽  
Chris S. M. Turney ◽  
Steve R. Rintoul ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Large Scale ◽  
Bottom Water ◽  
High Salinity ◽  
Satellite Observations ◽  
East Antarctica ◽  
Shelf Water ◽  
Antarctic Bottom Water ◽  
Glacier Tongue

Abstract. The dramatic calving of the Mertz Glacier tongue in 2010, precipitated by the movement of iceberg B09B, reshaped the oceanographic regime across the Mertz Polynya and Commonwealth Bay, regions where high-salinity shelf water (HSSW) – the precursor to Antarctic bottom water (AABW) – is formed. Here we present post-calving observations that suggest that this reconfiguration and subsequent grounding of B09B have driven the development of a new polynya and associated HSSW production off Commonwealth Bay. Supported by satellite observations and modelling, our findings demonstrate how local icescape changes may impact the formation of HSSW, with potential implications for large-scale ocean circulation.

scholarly journals Freshening of Antarctic Bottom Water Off Cape Darnley, East Antarctica

2020 ◽  
Vol 125 (8) ◽  
Author(s):  
S. Aoki ◽  
K. Katsumata ◽  
M. Hamaguchi ◽  
A. Noda ◽  
Y. Kitade ◽  
...  
Keyword(s):  
Bottom Water ◽  
East Antarctica ◽  
Antarctic Bottom Water

scholarly journals Flow of Antarctic Bottom water from the Vema Channel

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Eugene G. Morozov ◽  
Dmitry I. Frey ◽  
Roman Y. Tarakanov
Keyword(s):  
Continental Slope ◽  
Water Flow ◽  
North Atlantic ◽  
Bottom Water ◽  
The Other ◽  
Antarctic Bottom Water ◽  
The North ◽  
The North Atlantic ◽  
Current Flows ◽  
Western Wall

Abstract We analyze measurements of bottom currents and thermohaline properties of water north of the Vema Channel with the goal to find pathway continuations of Antarctic Bottom Water flow from the Vema Channel into the Brazil Basin. The analysis is based on CTD/LADCP casts north of the Vema Channel. The flow in the deep Vema Channel consists of two branches. The deepest current flows along the bottom in the center of the channel and the other branch flows above the western wall of the channel. We found two smaller channels of the northern continuation of the deeper bottom flow. These flows become weak and almost disappear at a latitude of 25° 30′ S. The upper current flows at a depth of 4100–4200 m along the continental slope. We traced this current up to 24° S over a distance exceeding 250 km. This branch transports bottom water that eventually fills the deep basins of the North Atlantic.

scholarly journals On deep convection events and Antarctic Bottom Water formation in ocean reanalysis products

Ocean Science ◽  
2017 ◽  
Vol 13 (6) ◽  
pp. 851-872 ◽  
Author(s):  
Wilton Aguiar ◽  
Mauricio M. Mata ◽  
Rodrigo Kerr
Keyword(s):  
Sea Ice ◽  
Bottom Water ◽  
Deep Convection ◽  
Open Ocean ◽  
Weddell Sea ◽  
Ocean Dynamics ◽  
Antarctic Bottom Water ◽  
Ocean Reanalysis ◽  
Reanalysis Product ◽  
Warm Deep Water

Abstract. Open ocean deep convection is a common source of error in the representation of Antarctic Bottom Water (AABW) formation in ocean general circulation models. Although those events are well described in non-assimilatory ocean simulations, the recent appearance of a massive open ocean polynya in the Estimating the Circulation and Climate of the Ocean Phase II reanalysis product (ECCO2) raises questions on which mechanisms are responsible for those spurious events and whether they are also present in other state-of-the-art assimilatory reanalysis products. To investigate this issue, we evaluate how three recently released high-resolution ocean reanalysis products form AABW in their simulations. We found that two of the products create AABW by open ocean deep convection events in the Weddell Sea that are triggered by the interaction of sea ice with the Warm Deep Water, which shows that the assimilation of sea ice is not enough to avoid the appearance of open ocean polynyas. The third reanalysis, My Ocean University Reading UR025.4, creates AABW using a rather dynamically accurate mechanism. The UR025.4 product depicts both continental shelf convection and the export of Dense Shelf Water to the open ocean. Although the accuracy of the AABW formation in this reanalysis product represents an advancement in the representation of the Southern Ocean dynamics, the differences between the real and simulated processes suggest that substantial improvements in the ocean reanalysis products are still needed to accurately represent AABW formation.

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