Summertime linkage between Antarctic sea-ice extent and ice-shelf basal melting through Antarctic coastal water masses’ variability: a circumpolar Southern Ocean model study

AbstractMuch attention has been paid to ocean–cryosphere interactions over the Southern Ocean. Basal melting of Antarctic ice shelves has been reported to be the primary ablation process for the Antarctic ice sheets. Warm waters on the continental shelf, such as Circumpolar Deep Water (CDW) and Antarctic Surface Water (AASW), play a critical role in active ice shelf basal melting. However, the temporal evolution and mechanisms of the basal melting and warm water intrusions throughout the twentieth century and the early twenty-first century have not been rigorously examined and are not fully understood. Here, we conduct a numerical experiment of an ocean–sea ice–ice shelf model forced with a century-long atmospheric reanalysis for the period 1900–2010. To begin with, we provide an assessment of the atmospheric conditions by comparing with available observation and show biases in warming and stronger westerly trends. Taking into account the limitation, we examine the interannual-to-multidecadal variability in the Antarctic ice shelf basal melting and the role of coastal water masses. A series of numerical experiments demonstrate that wind stress changes over the Southern Ocean drive enhanced poleward heat transport by stronger subpolar gyres and reduce coastal sea ice and cold-water formations, both of which result in an increased ocean heat flux into Antarctic ice shelf cavities. Furthermore, an increase of sea ice–free days leads to enhanced regional AASW contribution to the basal melting. This study demonstrates that changes in Antarctic coastal water masses are key metrics for better understanding of the ocean–cryosphere interaction over the Southern Ocean.

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A circumpolar coupled ocean – Antarctic ice sheet configuration for investigating recent changes in Southern Ocean heat content

10.5194/egusphere-egu2020-5647 ◽

2020 ◽

Author(s):

Charles Pelletier ◽

Lars Zipf ◽

Konstanze Haubner ◽

Hugues Goosse ◽

Frank Pattyn ◽

...

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Ice Sheet ◽

Heat Content ◽

Ice Shelf ◽

Sea Ice Extent ◽

Antarctic Ice Sheet ◽

Antarctic Sea Ice ◽

Physical Phenomena ◽

The Impact

From 2016 on, observed tendencies of Southern Ocean sea surface temperatures and Antarctic sea ice extent (SIE) have shifted from cooling down (with SIE increase) to warming up (SIE decrease). This change of Southern Ocean surface thermal properties has been sustained since, which indicates that it is not solely due to the interannual variability of the atmosphere, but also to modifications in the ocean itself. Among other physical phenomena, the acceleration of continental ice shelf melt, through its subsequent impact on the Southern Ocean stratification, has been proposed as one of the potential meaningful drivers of the sea ice changes. Reciprocally, recent studies suggest that besides atmosphere forcings, the upper ocean thermal content bears significant impact on ice shelf melt rates and dynamics. Here we present a new circumpolar coupled Southern Ocean &#8211; Antarctic ice sheet configuration aiming at investigating the impact of this ocean &#8211; continental ice feedback, developed within the framework of the PARAMOUR project. Our setting relies on the ocean and sea ice model NEMO3.6-LIM3 sending ice shelf melt rates to the Antarctic ice sheet model f.ETISh v1.5, who in turn responds to it and provides updated ice shelf cavity geometry. Both technical aspects and first coupled results are presented.

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Intercomparison of Antarctic ice-shelf, ocean, and sea-ice interactions simulated by MetROMS-iceshelf and FESOM 1.4

Geoscientific Model Development ◽

10.5194/gmd-11-1257-2018 ◽

2018 ◽

Vol 11 (4) ◽

pp. 1257-1292 ◽

Cited By ~ 9

Author(s):

Kaitlin A. Naughten ◽

Katrin J. Meissner ◽

Benjamin K. Galton-Fenzi ◽

Matthew H. England ◽

Ralph Timmermann ◽

...

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Water Mass ◽

Horizontal Resolution ◽

Ocean Model ◽

Small Scale ◽

Ice Shelf ◽

Vertical Coordinate ◽

Ice Shelves ◽

Basal Melting

Abstract. An increasing number of Southern Ocean models now include Antarctic ice-shelf cavities, and simulate thermodynamics at the ice-shelf/ocean interface. This adds another level of complexity to Southern Ocean simulations, as ice shelves interact directly with the ocean and indirectly with sea ice. Here, we present the first model intercomparison and evaluation of present-day ocean/sea-ice/ice-shelf interactions, as simulated by two models: a circumpolar Antarctic configuration of MetROMS (ROMS: Regional Ocean Modelling System coupled to CICE: Community Ice CodE) and the global model FESOM (Finite Element Sea-ice Ocean Model), where the latter is run at two different levels of horizontal resolution. From a circumpolar Antarctic perspective, we compare and evaluate simulated ice-shelf basal melting and sub-ice-shelf circulation, as well as sea-ice properties and Southern Ocean water mass characteristics as they influence the sub-ice-shelf processes. Despite their differing numerical methods, the two models produce broadly similar results and share similar biases in many cases. Both models reproduce many key features of observations but struggle to reproduce others, such as the high melt rates observed in the small warm-cavity ice shelves of the Amundsen and Bellingshausen seas. Several differences in model design show a particular influence on the simulations. For example, FESOM's greater topographic smoothing can alter the geometry of some ice-shelf cavities enough to affect their melt rates; this improves at higher resolution, since less smoothing is required. In the interior Southern Ocean, the vertical coordinate system affects the degree of water mass erosion due to spurious diapycnal mixing, with MetROMS' terrain-following coordinate leading to more erosion than FESOM's z coordinate. Finally, increased horizontal resolution in FESOM leads to higher basal melt rates for small ice shelves, through a combination of stronger circulation and small-scale intrusions of warm water from offshore.

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Intercomparison of Antarctic ice shelf, ocean, and sea ice interactions simulated by two models

10.5194/gmd-2017-268 ◽

2017 ◽

Author(s):

Kaitlin A. Naughten ◽

Katrin J. Meissner ◽

Benjamin K. Galton-Fenzi ◽

Matthew H. England ◽

Ralph Timmermann ◽

...

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Water Mass ◽

Horizontal Resolution ◽

Ocean Model ◽

Small Scale ◽

Ice Shelf ◽

Vertical Coordinate ◽

Ice Shelves ◽

Basal Melting

Abstract. An increasing number of Southern Ocean models now include Antarctic ice shelf cavities, and simulate thermodynamics at the ice-shelf/ocean interface. This adds another level of complexity to Southern Ocean simulations, as ice shelves interact directly with the ocean and indirectly with sea ice. Here we present the first published model intercomparison and evaluation of present-day ocean/sea-ice/ice-shelf interactions, as simulated by two models: a circumpolar Antarctic configuration of MetROMS (ROMS: Regional Ocean Modelling System coupled to CICE: Community Ice CodE) and the global model FESOM (Finite Element Sea-ice/ice-shelf Ocean Model), where the latter is run at two different levels of horizontal resolution. From a circumpolar Antarctic perspective, we compare and evaluate simulated ice shelf basal melting and sub-ice shelf circulation, as well as sea ice properties and Southern Ocean water mass characteristics as they influence the sub-ice shelf processes. Despite their differing numerical methods, the two models produce broadly similar results, and share similar biases in many cases. Both models reproduce many key features of observations, but struggle to reproduce others, such as the high melt rates observed in the small warm-cavity ice shelves of the Amundsen and Bellingshausen Seas. Several differences in model design show a particular influence on the simulations. For example, FESOM's greater topographic smoothing can alter the geometry of some ice shelf cavities enough to affect their melt rates; this improves at higher resolution, since less smoothing is required. In the interior Southern Ocean, the vertical coordinate system affects the degree of water mass erosion due to spurious diapycnal mixing, with MetROMS' terrain-following coordinates leading to more erosion than FESOM's z-coordinates. Finally, increased horizontal resolution in FESOM leads to higher basal melt rates for small ice shelves, through a combination of stronger circulation and small-scale intrusions of warm water from offshore.

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Last Glacial Maximum Antarctic sea ice linked with global mean ocean temperature: evidence from PMIP3, PMIP4 and MIROC-4m simulations

10.5194/egusphere-egu21-3550 ◽

2021 ◽

Author(s):

Tristan Vadsaria ◽

Sam Sherriff-Tadano ◽

Ayako Abe-Ouchi ◽

Takashi Obase ◽

Wing-Le Chan ◽

...

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Last Glacial Maximum ◽

Ocean Circulation ◽

Glacial Maximum ◽

Ocean Temperature ◽

Sea Ice Extent ◽

Last Glacial ◽

Antarctic Sea Ice ◽

The Antarctic

Southern Ocean sea ice and oceanic fronts are known to play an important role on the climate system, carbon cycles, bottom ocean circulation, and Antarctic ice sheet. However, many models of the previous Past-climate Model Intercomparison Project (PMIP) underestimated sea-ice extent (SIE) for the Last Glacial Maximum (LGM)(Roche et al., 2012; Marzocchi and Jensen, 2017), mainly because of surface bias (Flato et al., 2013) that may have an impact on mean ocean temperature (MOT). Indeed, recent studies further suggest an important link between Southern Ocean sea ice and mean ocean temperature (Ferrari et al., 2014; Bereiter et al., 2018 among others). Misrepresent the Antarctic sea-ice extent could highly impact deep ocean circulation, the heat transport and thus the MOT. In this study, we will stress the relationship between the distribution of Antarctic sea-ice extent and the MOT through the analysis of the PMIP3 and PMIP4 exercise and by using a set of MIROC models. To date, the latest version of MIROC improve its representation of the LGM Antarctic sea-ice extent, affecting the deep circulation and the MOT distribution (Sherriff-Tadano et al., under review).Our results show that available PMIP4 models have an overall improvement in term of LGM sea-ice extent compared to PMIP3, associated to colder deep and bottom ocean temperature. Focusing on MIROC (4m) models, we show that models accounting for Southern Ocean sea-surface temperature (SST) bias correction reproduce an Antarctic sea-ice extent, 2D-distribution, and seasonal amplitude in good agreement with proxy-based data. Finally, using PMIP-MIROC analyze, we show that it exists a relationship between the maximum SIE and the MOT, modulated by the Antarctic intermediate and bottom waters.

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Antarctic and Southern Ocean Sea-Ice and Climate Trends

Annals of Glaciology ◽

10.3189/s0260305500008417 ◽

1990 ◽

Vol 14 ◽

pp. 127-130 ◽

Cited By ~ 5

Author(s):

T.H Jacka

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Data Sets ◽

Climate Trends ◽

Sea Ice Extent ◽

Antarctic Sea Ice ◽

South Pacific Ocean ◽

Computer Based ◽

Long Term Trends

A computer-based climate monitoring project is described. Data sets include monthly and annual mean surface temperatures and pressures for occupied stations in Antarctica, the Southern Ocean and South Pacific Ocean; and monthly Antarctic sea-ice extent at each 10° of longitude.Simple statistical analyses of the data sets reveal a mean warming of ~0.15°C (10 a)−1 since the mid 1950s for Antarctic coastal stations and of ~0.04°C (10 a)−1 since the mid 1940s for the ocean stations. The sea-ice record from 1973 to 1988 reveals that the average northern ice limit has decreased at ~0.23°lat. (10 a)−1. Despite apparently compatible long-term trends of temperature and sea-ice extent, annual fluctuations of temperature and ice extent are highly variable and are not well correlated.

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The Response of the Southern Ocean and Antarctic Sea Ice to Freshwater from Ice Shelves in an Earth System Model

Journal of Climate ◽

10.1175/jcli-d-15-0501.1 ◽

2016 ◽

Vol 29 (5) ◽

pp. 1655-1672 ◽

Cited By ~ 45

Author(s):

Andrew G. Pauling ◽

Cecilia M. Bitz ◽

Inga J. Smith ◽

Patricia J. Langhorne

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Coupled Model ◽

Cmip5 Models ◽

Freshwater Flux ◽

Surface Mixed Layer ◽

Surface Cooling ◽

Ice Shelf ◽

Mass Imbalance ◽

Antarctic Sea Ice

ABSTRACT The possibility that recent Antarctic sea ice expansion resulted from an increase in freshwater reaching the Southern Ocean is investigated here. The freshwater flux from ice sheet and ice shelf mass imbalance is largely missing in models that participated in phase 5 of the Coupled Model Intercomparison Project (CMIP5). However, on average, precipitation minus evaporation (P − E) reaching the Southern Ocean has increased in CMIP5 models to a present value that is about greater than preindustrial times and 5–22 times larger than estimates of the mass imbalance of Antarctic ice sheets and shelves (119–544 ). Two sets of experiments were conducted from 1980 to 2013 in CESM1(CAM5), one of the CMIP5 models, artificially distributing freshwater either at the ocean surface to mimic iceberg melt or at the ice shelf fronts at depth. An anomalous reduction in vertical advection of heat into the surface mixed layer resulted in sea surface cooling at high southern latitudes and an associated increase in sea ice area. Enhancing the freshwater input by an amount within the range of estimates of the Antarctic mass imbalance did not have any significant effect on either sea ice area magnitude or trend. Freshwater enhancement of raised the total sea ice area by 1 × 106 km2, yet this and even an enhancement of was insufficient to offset the sea ice decline due to anthropogenic forcing for any period of 20 years or longer. Further, the sea ice response was found to be insensitive to the depth of freshwater injection.

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Dynamical mechanism of the poleward intensification of the Southern Hemispheric Westerlies due to sea ice extent change

10.5194/egusphere-egu2020-15627 ◽

2020 ◽

Author(s):

Hyeong-Gyu Kim ◽

Joowan Kim ◽

Sang-Yoon Jun ◽

Seong-Joong Kim

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Ocean Circulation ◽

Atmospheric Temperature ◽

Sea Ice Extent ◽

Dynamical Mechanism ◽

Antarctic Sea Ice ◽

Crucial Component ◽

Ice Conditions ◽

Geological Timescale

Paleoclimate data shows a good correlation between the concentration of CO2 and atmospheric temperature in the geological timescale. Many studies compare the Last Glacial Maximum (LGM) and the Pre-Industrial era (PI), to understand the coupling processes. A popular mechanism explaining this coupling process is a modulation of the ocean circulation and related CO2 emission over the Southern Ocean due to atmospheric westerly. The atmospheric westerly plays an important role in driving ocean circulation; however, the related processes are not fully understood for the LGM period.In this study, we examine physical processes determining the characteristics of the atmospheric westerly focusing on the Southern Ocean. Atmospheric states for LGM and PI are reproduced using a coupled earth system model with different sea ice conditions. A poleward intensification of the Southern Hemispheric Westerlies is observed for the LGM experiment. A comparison to PI shows that the meridional temperature gradient largely determines this intensification, and the enhanced meridional gradient is observed due to decreased heat flux from the subantarctic ocean in the LGM experiment. This result suggests that the Antarctic sea ice is a crucial component for understanding the Southern Hemispheric Westerly.

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Southern Ocean Sector Centennial Climate Variability and Recent Decadal Trends

Journal of Climate ◽

10.1175/jcli-d-12-00281.1 ◽

2013 ◽

Vol 26 (19) ◽

pp. 7767-7782 ◽

Cited By ~ 61

Author(s):

Mojib Latif ◽

Torge Martin ◽

Wonsun Park

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Atmospheric Circulation ◽

Climate Model ◽

Deep Convection ◽

Surface Air Temperature ◽

Weddell Sea ◽

Sea Ice Extent ◽

Low Level ◽

Antarctic Sea Ice

Abstract Evidence is presented for the notion that some contribution to the recent decadal trends observed in the Southern Hemisphere, including the lack of a strong Southern Ocean surface warming, may have originated from longer-term internal centennial variability originating in the Southern Ocean. The existence of such centennial variability is supported by the instrumental sea surface temperatures (SSTs), a multimillennial reconstruction of Tasmanian summer temperatures from tree rings, and a millennial control integration of the Kiel Climate Model (KCM). The model variability was previously shown to be linked to changes in Weddell Sea deep convection. During phases of deep convection the surface Southern Ocean warms, the abyssal Southern Ocean cools, Antarctic sea ice extent retreats, and the low-level atmospheric circulation over the Southern Ocean weakens. After the halt of deep convection the surface Southern Ocean cools, the abyssal Southern Ocean warms, Antarctic sea ice expands, and the low-level atmospheric circulation over the Southern Ocean intensifies, consistent with what has been observed during the recent decades. A strong sensitivity of the time scale to model formulation is noted. In the KCM, the centennial variability is associated with global-average surface air temperature (SAT) changes of the order of a few tenths of a degree per century. The model results thus suggest that internal centennial variability originating in the Southern Ocean should be considered in addition to other internal variability and external forcing when discussing the climate of the twentieth century and projecting that of the twenty-first century.

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Antarctic and Southern Ocean Sea-Ice and Climate Trends

Annals of Glaciology ◽

10.1017/s0260305500008417 ◽

1990 ◽

Vol 14 ◽

pp. 127-130 ◽

Cited By ~ 26

Author(s):

T.H Jacka

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Data Sets ◽

Climate Trends ◽

Sea Ice Extent ◽

Antarctic Sea Ice ◽

South Pacific Ocean ◽

Computer Based ◽

Long Term Trends

A computer-based climate monitoring project is described. Data sets include monthly and annual mean surface temperatures and pressures for occupied stations in Antarctica, the Southern Ocean and South Pacific Ocean; and monthly Antarctic sea-ice extent at each 10° of longitude. Simple statistical analyses of the data sets reveal a mean warming of ~0.15°C (10 a)−1 since the mid 1950s for Antarctic coastal stations and of ~0.04°C (10 a)−1 since the mid 1940s for the ocean stations. The sea-ice record from 1973 to 1988 reveals that the average northern ice limit has decreased at ~0.23°lat. (10 a)−1. Despite apparently compatible long-term trends of temperature and sea-ice extent, annual fluctuations of temperature and ice extent are highly variable and are not well correlated.

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