Uncertainty in the projected Antarctic contribution to sea level due to internal climate variability

Earth System Dynamics, Journal Year: 2025, Volume and Issue: 16(1), P. 293 - 315

Published: Feb. 18, 2025

Abstract. Identifying and quantifying irreducible reducible uncertainties in the Antarctic Ice Sheet (AIS) response to future climate change is essential for guiding mitigation adaptation policy decision. However, impact of internal variability, resulting from processes intrinsic system, remains poorly understood quantified. Here, we characterise both atmospheric oceanic variability a selection three Coupled Model Intercomparison Project Phase 6 (CMIP6) models (UKESM1-0-LL, IPSL-CM6A-LR, MPI-ESM1.2-HR) estimate their on contribution sea-level over 21st century under SSP2-4.5 scenario. To achieve this, use standalone ice-sheet model driven by ocean through parameterised basal melting atmosphere emulated surface mass balance estimates. The component Antarctica has similar amplitude CMIP6 models. In contrast, strongly depends its representation convective mixing ocean. A low bias sea-ice production an overly stratified lead lack deep which results weak near entrance ice-shelf cavities. Internal affects until 2100 45 % 93 depending model. This may be estimate, as CMIP likely underestimated. effect overwhelms dynamical loss factor 2 5, except Dronning Maud area Amundsen, Getz, Aurora basins, where contributions Based these results, recommend that projections consider (i) several members single account (ii) longer temporal period when correcting historical forcing match present-day observations.

Language: Английский

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Deep mixed ocean volume in the Labrador Sea in HighResMIP models

Climate Dynamics, Journal Year: 2021, Volume and Issue: 57(7-8), P. 1895 - 1918

Published: May 14, 2021

Abstract Simulations from seven global coupled climate models performed at high and standard resolution as part of the model intercomparison project (HighResMIP) are analyzed to study deep ocean mixing in Labrador Sea impact increased horizontal resolution. The representation convection varies strongly among models. Compared observations ARGO-floats EN4 data set, most substantially overestimate Sea. In four out five models, all using NEMO-ocean model, increasing 1° 1/4° leads Increasing atmospheric has a smaller effect than Simulated is mainly governed by release heat atmosphere vertical stratification water masses late autumn. Models with stronger sub-polar gyre circulation have generally higher surface salinity deeper convection. While high-resolution show more realistic they results indicate that sub-grid scale processes might be imperfect contribute biases Since half important for Atlantic Meridional Overturning Circulation (AMOC), this raises questions about future behavior AMOC

Language: Английский

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Southern Ocean polynyas in CMIP6 models

˜The œcryosphere, Journal Year: 2021, Volume and Issue: 15(9), P. 4281 - 4313

Published: Sept. 7, 2021

Abstract. Polynyas facilitate air–sea fluxes, impacting climate-relevant properties such as sea ice formation and deep water production. Despite their importance, polynyas have been poorly represented in past generations of climate models. Here we present a method to track the presence, frequency spatial distribution Southern Ocean 27 models participating Climate Model Intercomparison Project Phase 6 (CMIP6) two satellite-based products. Only half form open-water (OWPs), most underestimate area. As satellite observations, three show episodes high OWP activity separated by decades no OWP, while other unrealistically create OWPs nearly every year. In contrast, coastal polynya area is overestimated models, with least accurate representations occurring coarsest horizontal resolution. We that presence or absence linked changes regional hydrography, specifically linkages between convection and/or shoaling upper column thermocline. Models an Antarctic Circumpolar Current transport wind stress curl too frequent OWPs. Biases representation continue exist which has impact on ocean circulation ventilation should be addressed. However, emerging iceberg discharge schemes, more adequate vertical grid type overflow parameterisation are anticipated improve associated prediction future.

Language: Английский

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Influence of ocean tides and ice shelves on ocean–ice interactions and dense shelf water formation in the D’Urville Sea, Antarctica

Ocean Modelling, Journal Year: 2021, Volume and Issue: 162, P. 101794 - 101794

Published: March 26, 2021

Language: Английский

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Importance of the Antarctic Slope Current in the Southern Ocean Response to Ice Sheet Melt and Wind Stress Change

Journal of Geophysical Research Oceans, Journal Year: 2022, Volume and Issue: 127(5)

Published: April 28, 2022

Abstract We use two coupled climate models, GFDL‐CM4 and GFDL‐ESM4, to investigate the physical response of Southern Ocean changes in surface wind stress, Antarctic meltwater, combined forcing a pre‐industrial control simulation. The meltwater cools ocean all regions except Weddell Sea, where stress warms near‐surface layer. limited sensitivity Sea layer is due spatial distribution fluxes, regional bathymetry, large‐scale circulation patterns. dominates shelf models yield strikingly different responses along West Antarctica. disagreement attributable mean‐state representation meltwater‐driven acceleration Slope Current (ASC). In CM4, efficiently trapped on by well resolved, strong, accelerating ASC which isolates from warm offshore waters, leading strong subsurface cooling. ESM4, weaker diffuse allows more escape open ocean, does not become isolated, instead warming occurs. CM4 results suggest possible negative feedback mechanism that acts limit future melting, while ESM4 positive accelerate melt. Our demonstrate influence has governing shelf, highlighting importance coupling interactive ice sheet can resolve these dynamical processes.

Language: Английский

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An assessment of basal melt parameterisations for Antarctic ice shelves

˜The œcryosphere, Journal Year: 2022, Volume and Issue: 16(12), P. 4931 - 4975

Published: Dec. 14, 2022

Abstract. Ocean-induced ice-shelf melt is one of the largest uncertainty factors in Antarctic contribution to future sea-level rise. Several parameterisations exist, linking oceanic properties front ice shelf at base shelf, force ice-sheet models. Here, we assess potential a range these existing basal emulate rates simulated by cavity-resolving ocean model on circum-Antarctic scale. To do so, perform two cross-validations, over time and shelves respectively, re-tune perfect-model approach, compare produced newly tuned model. We find that quadratic dependence thermal forcing without dependency individual slope plume parameterisation yield best compromise, terms integrated spatial patterns. The box parameterisation, which separates sub-shelf circulation into boxes, PICOP combines with further from reference. linear cannot be recommended as resulting comparably furthest When using offshore hydrographic input fields comparison continental all worse; however, slope-dependent results. In addition new tuning, provide estimates for parameters.

Language: Английский

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Abruptly attenuated carbon sequestration with Weddell Sea dense waters by 2100

Nature Communications, Journal Year: 2022, Volume and Issue: 13(1)

Published: June 14, 2022

Abstract Antarctic Bottom Water formation, such as in the Weddell Sea, is an efficient vector for carbon sequestration on time scales of centuries. Possible changes under changing environmental conditions are unquantified to date, mainly due difficulties simulating relevant processes high-latitude continental shelves. Here, we use a model setup including both ice-shelf cavities and oceanic cycling demonstrate that by 2100, deep-ocean accumulation southern Sea abruptly attenuated only 40% 1990s rate high-emission scenario, while 2050s 2080s still 2.5-fold 4-fold higher, respectively, than 1990s. Assessing budgets water mass transformations, attribute this decline increased presence modified Warm Deep shelf, 16% reduction sea-ice 79% increase basal melt. Altogether, these lower density volume newly formed bottom waters reduce associated transport abyss.

Language: Английский

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Wind– and Sea‐Ice–Driven Interannual Variability of Antarctic Bottom Water Formation

Journal of Geophysical Research Oceans, Journal Year: 2023, Volume and Issue: 128(6)

Published: June 1, 2023

Abstract Antarctic Bottom Water (AABW) is a major component of the global overturning circulation, originating around continental margin. In recent decades AABW has both warmed and freshened, but there also evidence large interannual variability. The causes this underlying variability are not yet fully understood, in part due to lack ocean air‐sea‐ice flux measurements region. Here, we simulate formation export from 1958 2018 using global, eddying ocean–sea‐ice model which four regions transports agree reasonably well with observations. simulated exhibits strong correlated between different regions. Reservoirs very dense waters at depth Weddell Ross Seas following 1–2 years surface water mass transformation can lead higher for up decade. Prydz Bay Adélie Coast contrast, reservoirs do persist beyond 1 year attribute narrower shelf extent East main factor controlling high weaker easterly winds, reduce sea ice import into region, leaving increased areas open primed air‐sea buoyancy loss convective overturning. Our study highlights all regions, potential implications interpreting trends observational data only limited duration coverage.

Language: Английский

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Doubling of surface oceanic meridional heat transport by non-symmetry of mesoscale eddies

Nature Communications, Journal Year: 2023, Volume and Issue: 14(1)

Published: Sept. 6, 2023

Abstract Oceanic transport of heat by ubiquitous mesoscale eddies plays a critical role in regulating climate variability and redistributing excess absorbed ocean under global warming. Eddies have long been simplified as axisymmetric vortices their influence on remains unclear. Here, we combine satellite drifter data show that oceanic are asymmetric directionally-dependent, controlled self-sustaining nature dynamical environment. Both the direction amplitude eddy-induced fluxes significantly influenced eddy’s asymmetry directional dependence. When eddy velocity field is decomposed into symmetric components, kinetic energy exhibits nearly equal partition between these two components. The total meridional flux similarly doubles induced highlighting crucial contribution magnitude transport.

Language: Английский

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Observing Antarctic Bottom Water in the Southern Ocean

Frontiers in Marine Science, Journal Year: 2023, Volume and Issue: 10

Published: Dec. 8, 2023

Dense, cold waters formed on Antarctic continental shelves descend along the margin, where they mix with other Southern Ocean to form Bottom Water (AABW). AABW then spreads into deepest parts of all major ocean basins, isolating heat and carbon from atmosphere for centuries. Despite AABW’s key role in regulating Earth’s climate long time scales recording conditions, remains poorly observed. This lack observational data is mostly due two factors. First, originates shelf slope situ measurements are limited observations by satellites hampered persistent sea ice cover periods darkness winter. Second, north slope, found below approximately 2 km depth, also scarce cannot provide direct measurements. Here, we review progress made during past decades observing AABW. We describe 1) long-term monitoring obtained moorings, ship-based surveys, beneath through bore holes; 2) recent development autonomous tools coastal deep systems; 3) alternative approaches including assimilation models satellite-derived proxies. The variety beginning transform our understanding AABW, its formation processes, temporal variability, contribution lower limb global meridional overturning circulation. In particular, these highlight played winds, ice, Ice Sheet AABW-related processes. conclude discussing future avenues impressing need a sustained coordinated system.

Language: Английский

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