Inter-hemispheric asymmetry in the sea-ice response to volcanic forcing simulated by MPI-ESM (COSMOS-Mill)

Abstract. The decadal evolution of Arctic and Antarctic sea ice following strong volcanic eruptions is investigated in four climate simulation ensembles performed with the COSMOS-Mill version of the Max Planck Institute-Earth System Model. The ensembles differ in the magnitude of the imposed volcanic perturbations, with sizes representative of historical tropical eruptions (1991 Pinatubo and 1815 Tambora) and of tropical and extra-tropical "supervolcano" eruptions. A post-eruption Arctic sea-ice expansion is robustly detected in all ensembles, while Antarctic sea ice responds only to "supervolcano" eruptions, undergoing an initial short-lived expansion and a subsequent prolonged contraction phase. Strong volcanic forcing therefore emerges as a potential source of inter-hemispheric interannual-to-decadal climate variability, although the inter-hemispheric signature is weak in the case of historical-size eruptions. The post-eruption inter-hemispheric decadal asymmetry in sea ice is interpreted as a consequence mainly of different exposure of Arctic and Antarctic regional climates to induced meridional heat transport changes and of dominating local feedbacks that set in within the Antarctic region. "Supervolcano" experiments help clarifying differences in simulated hemispheric internal dynamics related to imposed negative net radiative imbalances, including the relative importance of the thermal and dynamical components of the sea-ice response. "Supervolcano" experiments could therefore serve the assessment of climate models' behavior under strong external forcing conditions and, consequently, favor advancements in our understanding of simulated sea-ice dynamics.

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Observed Concentration Budgets of Arctic and Antarctic Sea Ice

Journal of Climate ◽

10.1175/jcli-d-16-0121.1 ◽

2016 ◽

Vol 29 (14) ◽

pp. 5241-5249 ◽

Cited By ~ 13

Author(s):

Paul R. Holland ◽

Noriaki Kimura

Keyword(s):

Sea Ice ◽

Climate Models ◽

Arctic Sea Ice ◽

Ice Melting ◽

Antarctic Sea Ice ◽

Arctic Sea ◽

Ice Concentration ◽

Anthropogenic Contribution ◽

Ice Edge ◽

The Antarctic

Abstract In recent decades, Antarctic sea ice has expanded slightly while Arctic sea ice has contracted dramatically. The anthropogenic contribution to these changes cannot be fully assessed unless climate models are able to reproduce them. Process-based evaluation is needed to provide a clear view of the capabilities and limitations of such models. In this study, ice concentration and drift derived from AMSR-E data during 2003–10 are combined to derive a climatology of the ice concentration budget at both poles. This enables an observational decomposition of the seasonal dynamic and thermodynamic changes in ice cover. In both hemispheres, the results show spring ice loss dominated by ice melting. In other seasons ice divergence maintains freezing in the inner pack while advection causes melting at the ice edge, as ice is transported beyond the region where it is thermodynamically sustainable. Mechanical redistribution provides an important sink of ice concentration in the central Arctic and around the Antarctic coastline. This insight builds upon existing understanding of the sea ice cycle gained from ice and climate models, and the datasets may provide a valuable tool in validating such models in the future.

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Present-Day Arctic Sea Ice Variability in the Coupled ECHAM5/MPI-OM Model

Journal of Climate ◽

10.1175/2009jcli3065.1 ◽

2010 ◽

Vol 23 (10) ◽

pp. 2520-2543 ◽

Cited By ~ 16

Author(s):

Nikolay V. Koldunov ◽

Detlef Stammer ◽

Jochem Marotzke

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Ocean Circulation ◽

Climate Models ◽

Climate Model ◽

Heat Content ◽

Arctic Sea Ice ◽

The Arctic ◽

Max Planck ◽

Arctic Sea

Abstract As a contribution to a detailed evaluation of Intergovernmental Panel on Climate Change (IPCC)-type coupled climate models against observations, this study analyzes Arctic sea ice parameters simulated by the Max-Planck-Institute for Meteorology (MPI-M) fully coupled climate model ECHAM5/Max-Planck-Institute for Meteorology Hamburg Primitive Equation Ocean Model (MPI-OM) for the period from 1980 to 1999 and compares them with observations collected during field programs and by satellites. Results of the coupled run forced by twentieth-century CO2 concentrations show significant discrepancies during summer months with respect to observations of the spatial distribution of the ice concentration and ice thickness. Equally important, the coupled run lacks interannual variability in all ice and Arctic Ocean parameters. Causes for such big discrepancies arise from errors in the ECHAM5/MPI-OM atmosphere and associated errors in surface forcing fields (especially wind stress). This includes mean bias pattern caused by an artificial circulation around the geometric North Pole in its atmosphere, as well as insufficient atmospheric variability in the ECHAM5/MPI-OM model, for example, associated with Arctic Oscillation/North Atlantic Oscillation (AO/NAO). In contrast, the identical coupled ocean–ice model, when driven by NCEP–NCAR reanalysis fields, shows much increased skill in its ice and ocean circulation parameters. However, common to both model runs is too strong an ice export through the Fram Strait and a substantially biased heat content in the interior of the Arctic Ocean, both of which may affect sea ice budgets in centennial projections of the Arctic climate system.

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Faster Arctic Sea Ice Retreat in CMIP5 than in CMIP3 due to Volcanoes

Journal of Climate ◽

10.1175/jcli-d-16-0391.1 ◽

2016 ◽

Vol 29 (24) ◽

pp. 9179-9188 ◽

Cited By ~ 18

Author(s):

Erica Rosenblum ◽

Ian Eisenman

Keyword(s):

Sea Ice ◽

Climate Models ◽

Arctic Sea Ice ◽

Sea Ice Extent ◽

Arctic Sea ◽

Volcanic Forcing ◽

Global Mean Surface Temperature ◽

Ice Retreat ◽

Sea Ice Retreat ◽

Global Mean

Abstract The downward trend in Arctic sea ice extent is one of the most dramatic signals of climate change during recent decades. Comprehensive climate models have struggled to reproduce this trend, typically simulating a slower rate of sea ice retreat than has been observed. However, this bias has been widely noted to have decreased in models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5) compared with the previous generation of models (CMIP3). Here simulations are examined from both CMIP3 and CMIP5. It is found that simulated historical sea ice trends are influenced by volcanic forcing, which was included in all of the CMIP5 models but in only about half of the CMIP3 models. The volcanic forcing causes temporary simulated cooling in the 1980s and 1990s, which contributes to raising the simulated 1979–2013 global-mean surface temperature trends to values substantially larger than observed. It is shown that this warming bias is accompanied by an enhanced rate of Arctic sea ice retreat and hence a simulated sea ice trend that is closer to the observed value, which is consistent with previous findings of an approximately linear relationship between sea ice extent and global-mean surface temperature. Both generations of climate models are found to simulate Arctic sea ice that is substantially less sensitive to global warming than has been observed. The results imply that much of the difference in Arctic sea ice trends between CMIP3 and CMIP5 occurred because of the inclusion of volcanic forcing, rather than improved sea ice physics or model resolution.

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Advances in Understanding the Sea Ice Floe Size Distribution

10.26686/wgtn.17135921.v1 ◽

2021 ◽

Author(s):

◽

Laetitia Roach

Keyword(s):

Sea Ice ◽

Size Distribution ◽

Climate Models ◽

Arctic Sea Ice ◽

Climate System ◽

Model Parameters ◽

Physical Processes ◽

Sea Ice Concentration ◽

Ice Dynamics ◽

Polar Climate

Sea ice is a critical component of the polar climate system that is tightly coupled to the ocean and atmosphere. It is highly heterogeneous, composed of discrete floes which range in size across space and time. In this thesis, I use a combination of modelling and observational approaches to investigate how different physical processes determine the distribution of sea ice floe sizes. I construct the first global model that simulates floe sizes arising from the interaction of different physical processes. Floe sizes are modified by lateral melt, lateral growth, freezing together of floes and wave-ice interactions. By grounding process descriptions in underlying physics, observations of individual processes can be used to constrain model parameters. In light of the sparseness of floe size observations, I developed a novel methodology to constrain previously-unobserved floe freezing processes from in-situ observations. Results from global coupled sea ice–ocean model simulations are used to quantify the relative impacts of different processes on spatial and seasonal variability in the floe size distribution, providing hypotheses that could be tested by observational campaigns in the future. Under transient historical forcing, the model suggests that the fragmentation of Arctic sea ice has significantly increased over the satellite era. I also seek to improve understanding of feedbacks between sea ice floe size and the polar climate system. A fragmented ice cover exposes more ice area on the sides of floes to the ocean than sheet ice, promoting lateral melt, which reduces surface albedo. Conducting a statistical analysis of current climate models shows that inclusion of a lateral melt parametrization improves simulation of sea ice concentration relative to observations. However, calculation of lateral melt using the model for prognostic simulation of the sub-grid-scale floe size distribution results in little or no enhancement of lateral melt at a hemispheric scale compared to a simple parametrization, although it is likely to be important at smaller spatial and shorter temporal scales. The new model opens up the possibility of coupling sea ice and ocean surface wave models and of including floe size dependence in other processes, such as form drag, sea ice dynamics, ocean eddies and ocean–atmosphere heat transfer, which may result in significant impacts for polar climate.

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The relative roles of Arctic and Antarctic sea-ice loss in the response to greenhouse warming

10.5194/egusphere-egu21-16310 ◽

2021 ◽

Author(s):

Stephanie Hay ◽

Paul Kusnher

Keyword(s):

Sea Ice ◽

Climate Models ◽

Climate Model ◽

Arctic Sea Ice ◽

The Arctic ◽

Sea Ice Extent ◽

Antarctic Sea Ice ◽

Arctic Sea ◽

Climate Model Simulations ◽

Arctic Sea Ice Loss

Antarctic sea ice has gradually increased in extent over the forty-year-long satellite record, in contrast with the clear decrease in sea-ice extent seen in the Arctic over the same time period. However, state-of-the-art climate models ubiquitously project Antarctic sea-ice to decrease over the coming century, much as they do for Arctic sea-ice. Several recent years have also seen record low Antarctic sea-ice. It is therefore of interest to understand what the climate response to Antarctic sea-ice loss will be.&#160;We have carried out new fully coupled climate model simulations to assess the response to sea-ice loss in either hemisphere separately or coincidentally under different albedo parameter settings to determine the relative importance of each. By perturbing the albedo of the snow overlying the sea ice and the albedo of the bare sea ice, we obtain a suite of simulations to assess the linearity and additivity of sea-ice loss. We find the response to sea-ice loss in each hemisphere exhibits a high degree of additivity, and can simply be decomposed into responses due to loss in each hemisphere separately.&#160;We find that the response to Antarctic sea-ice loss exceeds that of Arctic sea-ice loss in the tropics, and that Antarctic sea-ice loss leads to statistically significant Arctic warming, while the opposite is not true.With these new simulations and one in which CO2 is instantaneously doubled , we can further characterize the response to sea-ice loss from each hemisphere using an extension to classical pattern scaling that includes three controlling parameters. This allows us to simultaneously compute the sensitivity patterns to Arctic sea-ice loss, Antarctic sea-ice loss, and to tropical warming. The statistically significant response to Antarctic sea-ice loss in the Northern Hemisphere extratropics is found to be mediated by tropical warming and small amounts of Arctic sea-ice loss.

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Making informed use of observations and climate models to advance understanding of past and future sea ice changes

10.5194/egusphere-egu21-207 ◽

2021 ◽

Author(s):

Francois Massonnet

Keyword(s):

Sea Ice ◽

Climate Models ◽

Arctic Sea Ice ◽

Satellite Observations ◽

Polar Regions ◽

Antarctic Sea Ice ◽

Arctic Sea ◽

Big Picture ◽

Assimilation Model

Polar Regions are viewed by many as "observational deserts", as in-situ measurements there are indeed scarce relative to other regions. The increasing availability of satellite observations does not entirely solve the problem, due to persistent uncertainties in the derived products. Climate models have been instrumental in completing the big picture, but they are themselves subject to errors, some of which are systematic. How to take advantage of the respective strengths of observations and models, while minimizing their respective weaknesses? &#160;To illustrate this point, I will discuss how recent advances in data assimilation, model evaluation, and numerical modeling have enabled progress on addressing important questions in polar research, such as: what are the causes of the recent Antarctic sea ice variability? What might the future of Arctic sea ice look like? How to improve the skill of seasonal sea ice predictions? How should the existing observational network be improved at high latitudes? What are the priorities in terms of modeling? By running through these cases, I will provide support for the emerging hypothesis that "the whole is greater than the sum of its parts": treating observations and climate models as two noisy instances of the same, unknown truth, gives access to answers that would not have been possible using each source separately.

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Arctic and Antarctic Sea Ice Change: Contrasts, Commonalities, and Causes

Annual Review of Marine Science ◽

10.1146/annurev-marine-010816-060610 ◽

2019 ◽

Vol 11 (1) ◽

pp. 187-213 ◽

Cited By ~ 20

Author(s):

Ted Maksym

Keyword(s):

Sea Ice ◽

Climate Models ◽

Ice Cover ◽

Natural Variability ◽

Arctic Sea Ice ◽

Regional Variability ◽

Antarctic Sea Ice ◽

Induced Changes ◽

Natural Climate ◽

The Impact

Arctic sea ice has declined precipitously in both extent and thickness over the past four decades; by contrast, Antarctic sea ice has shown little overall change, but this masks large regional variability. Climate models have not captured these changes. But these differences do not represent a paradox. The processes governing, and impacts of, natural variability and human-induced changes differ markedly at the poles largely because of the ways in which differences in geography control the properties of and interactions among the atmosphere, ice, and ocean. The impact of natural variability on the ice cover is large at both poles, so modeled ice trends are not entirely inconsistent with contributions from both natural variability and anthropogenic forcing. Despite this concurrence, the coupling of natural climate variability, climate feedbacks, and sea ice is not well understood, and significant biases remain in model representations of the ice cover and the processes that drive it.

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Advances in Understanding the Sea Ice Floe Size Distribution

10.26686/wgtn.17135921 ◽

2021 ◽

Author(s):

◽

Laetitia Roach

Keyword(s):

Sea Ice ◽

Size Distribution ◽

Climate Models ◽

Arctic Sea Ice ◽

Climate System ◽

Model Parameters ◽

Physical Processes ◽

Sea Ice Concentration ◽

Ice Dynamics ◽

Polar Climate

Sea ice is a critical component of the polar climate system that is tightly coupled to the ocean and atmosphere. It is highly heterogeneous, composed of discrete floes which range in size across space and time. In this thesis, I use a combination of modelling and observational approaches to investigate how different physical processes determine the distribution of sea ice floe sizes. I construct the first global model that simulates floe sizes arising from the interaction of different physical processes. Floe sizes are modified by lateral melt, lateral growth, freezing together of floes and wave-ice interactions. By grounding process descriptions in underlying physics, observations of individual processes can be used to constrain model parameters. In light of the sparseness of floe size observations, I developed a novel methodology to constrain previously-unobserved floe freezing processes from in-situ observations. Results from global coupled sea ice–ocean model simulations are used to quantify the relative impacts of different processes on spatial and seasonal variability in the floe size distribution, providing hypotheses that could be tested by observational campaigns in the future. Under transient historical forcing, the model suggests that the fragmentation of Arctic sea ice has significantly increased over the satellite era. I also seek to improve understanding of feedbacks between sea ice floe size and the polar climate system. A fragmented ice cover exposes more ice area on the sides of floes to the ocean than sheet ice, promoting lateral melt, which reduces surface albedo. Conducting a statistical analysis of current climate models shows that inclusion of a lateral melt parametrization improves simulation of sea ice concentration relative to observations. However, calculation of lateral melt using the model for prognostic simulation of the sub-grid-scale floe size distribution results in little or no enhancement of lateral melt at a hemispheric scale compared to a simple parametrization, although it is likely to be important at smaller spatial and shorter temporal scales. The new model opens up the possibility of coupling sea ice and ocean surface wave models and of including floe size dependence in other processes, such as form drag, sea ice dynamics, ocean eddies and ocean–atmosphere heat transfer, which may result in significant impacts for polar climate.

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Making an informed use of observations and climate models to advance understanding of past and future sea ice changes

10.5194/egusphere-egu2020-14046 ◽

2020 ◽

Author(s):

François Massonnet

Keyword(s):

Sea Ice ◽

Climate Models ◽

Arctic Sea Ice ◽

Polar Regions ◽

Antarctic Sea Ice ◽

Arctic Sea ◽

Big Picture ◽

Assimilation Model ◽

Major Progress

Polar Regions are viewed by many as "observational deserts", as in-situ measurements there are indeed scarce relative to other regions. The increasing availability of satellite observations is salutary but does not entirely solve the problem due to persistent uncertainties in the derived products. Climate models have been instrumental in completing the big picture. However, models are themselves subject to errors, some of which are systematic. How to take advantage of the respective strengths of observations and models, while minimizing their respective weaknesses? To illustrate this point, I will discuss how recent advances in data assimilation, model evaluation, and numerical modeling have enabled major progress in tackling important questions in polar research, such as: What are the causes of the recent Antarctic sea ice variability? What might the future of Arctic sea ice look like? How to improve the skill of seasonal sea ice predictions? How should the existing observational network be improved at high latitudes? What are the priorities in terms of sea ice modeling for climate change studies? By running through these cases, I will provide evidence for the emerging hypothesis that "the whole is greater than the sum of its parts": treating observations and climate models as two noisy instances of the same, but unknown truth, gives insights that would not be possible if each source was used separately.

Download Full-text