scholarly journals Consistent Changes in the Sea Ice Seasonal Cycle in Response to Global Warming

2011 ◽  
Vol 24 (20) ◽  
pp. 5325-5335 ◽  
Author(s):  
Ian Eisenman ◽  
Tapio Schneider ◽  
David S. Battisti ◽  
Cecilia M. Bitz
Keyword(s):  
Sea Ice ◽  
Northern Hemisphere ◽  
Surface Albedo ◽  
Climate Models ◽  
Climate Model ◽  
Ice Cover ◽  
Climate Forcing ◽  
Sea Ice Extent ◽  
Ice Retreat ◽  
Sea Ice Retreat

Abstract The Northern Hemisphere sea ice cover has diminished rapidly in recent years and is projected to continue to diminish in the future. The year-to-year retreat of Northern Hemisphere sea ice extent is faster in summer than winter, which has been identified as one of the most striking features of satellite observations as well as of state-of-the-art climate model projections. This is typically understood to imply that the sea ice cover is most sensitive to climate forcing in summertime, and previous studies have explained this by calling on factors such as the surface albedo feedback. In the Southern Hemisphere, however, it is the wintertime sea ice extent that retreats fastest in climate model projections. Here, it is shown that the interhemispheric differences in the model projections can be attributed to differences in coastline geometry, which constrain where sea ice can occur. After accounting for coastline geometry, it is found that the sea ice changes simulated in both hemispheres in most climate models are consistent with sea ice retreat being fastest in winter in the absence of landmasses. These results demonstrate that, despite the widely differing rates of ice retreat among climate model projections, the seasonal structure of the sea ice retreat is robust among the models and is uniform in both hemispheres.

scholarly journals Sea-ice and North Atlantic climate response to CO2-induced warming and cooling conditions

2006 ◽  
Vol 52 (178) ◽  
pp. 433-439 ◽  
Author(s):  
Larissa Nazarenko ◽  
Nickolai Tausnev ◽  
James Hansen
Keyword(s):  
Sea Ice ◽  
Northern Hemisphere ◽  
Surface Pressure ◽  
Climate Model ◽  
Global Climate Model ◽  
Ice Cover ◽  
The Arctic ◽  
Normal Surface ◽  
Sea Ice Extent ◽  
Polar Cell

AbstractUsing a global climate model coupled with an ocean and a sea-ice model, we compare the effects of doubling CO2 and halving CO2 on sea-ice cover and connections with the atmosphere and ocean. An overall warming in the 2 × CO2 experiment causes reduction of sea-ice extent by 15%, with maximum decrease in summer and autumn, consistent with observed seasonal sea-ice changes. The intensification of the Northern Hemisphere circulation is reflected in the positive phase of the Arctic Oscillation (AO), associated with higher-than-normal surface pressure south of about 50° N and lower-than-normal surface pressure over the high northern latitudes. Strengthening the polar cell causes enhancement of westerlies around the Arctic perimeter during winter. Cooling, in the 0.5 × CO2 experiment, leads to thicker and more extensive sea ice. In the Southern Hemisphere, the increase in ice-covered area (28%) dominates the ice-thickness increase (5%) due to open ocean to the north. In the Northern Hemisphere, sea-ice cover increases by only 8% due to the enclosed land/sea configuration, but sea ice becomes much thicker (108%). Substantial weakening of the polar cell due to increase in sea-level pressure over polar latitudes leads to a negative trend of the winter AO index. The model reproduces large year-to-year variability under both cooling and warming conditions.

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

2016 ◽  
Vol 29 (24) ◽  
pp. 9179-9188 ◽  
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.

scholarly journals The Role of Northern Sea Ice Cover for the Weakening of the Thermohaline Circulation under Global Warming

2007 ◽  
Vol 20 (16) ◽  
pp. 4160-4171 ◽  
Author(s):  
A. Levermann ◽  
J. Mignot ◽  
S. Nawrath ◽  
S. Rahmstorf
Keyword(s):  
Global Warming ◽  
Sea Ice ◽  
Heat Loss ◽  
Climate Models ◽  
Thermohaline Circulation ◽  
Ice Cover ◽  
Near Surface ◽  
Ice Retreat ◽  
Sea Ice Retreat

Abstract An increase in atmospheric CO2 concentration and the resulting global warming are typically associated with a weakening of the thermohaline circulation (THC) in model scenarios. For the models participating in the Coupled Model Intercomparison Project (CMIP), this weakening shows a significant (r = 0.62) dependence on the initial THC strength; it is stronger for initially strong overturning. The authors propose a physical mechanism for this phenomenon based on an analysis of additional simulations with the coupled climate models CLIMBER-2 and CLIMBER-3α. The mechanism is based on the fact that sea ice cover greatly reduces heat loss from the ocean. The extent of sea ice is strongly influenced by the near-surface atmospheric temperature (SAT) in the North Atlantic but also by the strength of the THC itself, which transports heat to the convection sites. Consequently, sea ice tends to extend farther south for weaker THC. Initially larger sea ice cover responds more strongly to atmospheric warming; thus, sea ice retreats more strongly for an initially weaker THC. This sea ice retreat tends to strengthen (i.e., stabilize) the THC because the sea ice retreat allows more oceanic heat loss. This stabilizing effect is stronger for runs with weak initial THC and extensive sea ice cover. Therefore, an initially weak THC weakens less under global warming. In contrast to preindustrial climate, sea ice melting presently plays the role of an external forcing with respect to THC stability.

Assessing Prior Emergent Constraints on Surface Albedo Feedback in CMIP6

2021 ◽  
Vol 34 (10) ◽  
pp. 3889-3905
Author(s):  
Chad W. Thackeray ◽  
Alex Hall ◽  
Mark D. Zelinka ◽  
Christopher G. Fletcher
Keyword(s):  
Sea Ice ◽  
Snow Cover ◽  
Surface Albedo ◽  
Climate Models ◽  
Sea Ice Thickness ◽  
Albedo Feedback ◽  
Out Of Sample ◽  
Ice Retreat ◽  
Sea Ice Retreat ◽  
Emergent Constraint

AbstractAn emergent constraint (EC) is a popular model evaluation technique, which offers the potential to reduce intermodel variability in projections of climate change. Two examples have previously been laid out for future surface albedo feedbacks (SAF) stemming from loss of Northern Hemisphere (NH) snow cover (SAFsnow) and sea ice (SAFice). These processes also have a modern-day analog that occurs each year as snow and sea ice retreat from their seasonal maxima, which is strongly correlated with future SAF across an ensemble of climate models. The newly released CMIP6 ensemble offers the chance to test prior constraints through out-of-sample verification, an important examination of EC robustness. Here, we show that the SAFsnow EC is equally strong in CMIP6 as it was in past generations, while the SAFice EC is also shown to exist in CMIP6, but with different, slightly weaker characteristics. We find that the CMIP6 mean NH SAF exhibits a global feedback of 0.25 ± 0.05 W m−2 K−1, or ~61% of the total global albedo feedback, largely in line with prior generations despite its increased climate sensitivity. The NH SAF can be broken down into similar contributions from snow and sea ice over the twenty-first century in CMIP6. Crucially, intermodel variability in seasonal SAFsnow and SAFice is largely unchanged from CMIP5 because of poor outlier simulations of snow cover, surface albedo, and sea ice thickness. These outliers act to mask the noted improvement from many models when it comes to SAFice, and to a lesser extent SAFsnow.

scholarly journals A spurious jump in the satellite record: is Antarctic sea ice really expanding?

2014 ◽  
Vol 8 (1) ◽  
pp. 273-288 ◽  
Author(s):  
I. Eisenman ◽  
W. N. Meier ◽  
J. R. Norris
Keyword(s):  
Sea Ice ◽  
Ice Cover ◽  
The Arctic ◽  
Sea Ice Extent ◽  
Physical Mechanisms ◽  
Antarctic Sea Ice ◽  
Ice Retreat ◽  
Bootstrap Algorithm ◽  
Sea Ice Retreat ◽  
The Antarctic

Abstract. Recent estimates indicate that the Antarctic sea ice cover is expanding at a statistically significant rate with a magnitude one third as large as the rapid rate of sea ice retreat in the Arctic. However, during the mid-2000s, with several fewer years in the observational record, the trend in Antarctic sea ice extent was reported to be considerably smaller and statistically indistinguishable from zero. Here, we show that the increase in the reported trend occurred primarily due to the effect of a previously undocumented change in the way the satellite sea ice observations are processed for the widely-used Bootstrap algorithm dataset, rather than a physical increase in the rate of ice advance. Although our analysis does not definitively identify whether this undocumented change introduced an error or removed one, the resulting difference in the trends suggests that a substantial error exists in either the current dataset or the version that was used prior to the mid-2000s, and numerous studies that have relied on these observations should be reexamined to determine the sensitivity of their results to this change in the dataset. Furthermore, a number of recent studies have investigated physical mechanisms for the observed expansion of the Antarctic sea ice cover. The results of this analysis raise the possibility that this expansion may be a spurious artifact of an error in the satellite observations, and that the actual Antarctic sea ice cover may not be expanding at all.

Do Climate Models Underestimate the Sensitivity of Northern Hemisphere Sea Ice Cover?

2011 ◽  
Vol 24 (15) ◽  
pp. 3924-3934 ◽  
Author(s):  
Michael Winton
Keyword(s):  
Sea Ice ◽  
Northern Hemisphere ◽  
Climate Models ◽  
Climate Model ◽  
Ice Cover ◽  
Natural Variability ◽  
Global Temperature ◽  
Temperature Trends ◽  
Gfdl Model ◽  
The Impact

Abstract The sensitivity of Northern Hemisphere sea ice cover to global temperature change is examined in a group of climate models and in the satellite-era observations. The models are found to have well-defined, distinguishable sensitivities in climate change experiments. The satellite-era observations show a larger sensitivity—a larger decline per degree of warming—than any of the models. To evaluate the role of natural variability in this discrepancy, the sensitivity probability density function is constructed based upon the observed trends and natural variability of multidecadal ice cover and global temperature trends in a long control run of the GFDL Climate Model, version 2.1 (CM2.1). This comparison shows that the model sensitivities range from about 1 to more than 2 pseudostandard deviations of the variability smaller than observations indicate. The impact of natural Atlantic multidecadal temperature trends (as simulated by the GFDL model) on the sensitivity distribution is examined and found to be minimal.

scholarly journals Response of the Northern Hemisphere sea ice to greenhouse forcing in a global climate model

2001 ◽  
Vol 33 ◽  
pp. 513-520 ◽  
Author(s):  
Larissa Nazarenko ◽  
James Hansen ◽  
Nikolai Tausnev ◽  
Reto Ruedy
Keyword(s):  
Sea Ice ◽  
Northern Hemisphere ◽  
General Circulation ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Circulation Model ◽  
High Sensitivity ◽  
Ice Cover ◽  
Sea Ice Extent

AbstractThe Q.-flux Goddard Institute of Space Studies (GISS) global climate model, in which an atmospheric general circulation model is coupled to a mixed-layer ocean with specified horizontal heat transports, is used to simulate the transient and equilibrium climate response to a gradual increase of carbon dioxide (1% per year increase of CO2 to doubled CO2). The results indicate that the current GISS model has a high sensitivity with a global annual warming of about 4°C for doubled CO2 . Enhanced warming is found at higher latitudes near sea-ice margins due to retreat of sea ice in the greenhouse experiment. Surface warming is larger in winter than in summer, in part because of the reductions in ice cover and thickness that insulate the winter atmosphere from the ocean. The annual mean reduction of sea-ice cover due to doubled CO2 is about 30% for the Northern Hemisphere. The CO2 experiment has a 70% reduction of sea-ice area and 55% thinning of ice in August in the Northern Hemisphere. Noticeable reduction of sea-ice cover has been found in both historical records and satellite observations. The largest reduction of simulated sea-ice extent occurs in summer, consistent with observations.

scholarly journals The Response of the Nordic Seas to Wintertime Sea-ice Retreat

2021 ◽  
pp. 1-40
Author(s):  
Yue Wu ◽  
David P. Stevens ◽  
Ian A. Renfrew ◽  
Xiaoming Zhai
Keyword(s):  
Global Warming ◽  
Sea Ice ◽  
Climate Model ◽  
Sea Temperature ◽  
Nordic Seas ◽  
Ocean Response ◽  
Marginal Ice Zone ◽  
Ice Retreat ◽  
Ice Edge ◽  
Sea Ice Retreat

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.

A 14 - 0 ka record of trends and events of sea ice cover, primary production and freshwater discharge in the Beaufort Sea, Arctic Ocean

2020 ◽  
Author(s):  
Junjie Wu ◽  
Ruediger Stein ◽  
Kirsten Fahl ◽  
Nicole Syring ◽  
Jens Hefter ◽  
...  
Keyword(s):  
Sea Ice ◽  
Primary Production ◽  
Beaufort Sea ◽  
Ice Cover ◽  
Sediment Flux ◽  
The Arctic ◽  
Proxy Records ◽  
Ice Retreat ◽  
Sea Ice Retreat ◽  
Natural Climate

<p>The Arctic is changing rapidly, and one of the main and most obvious features is the drastic sea-ice retreat over the past few decades. Over such time scales, observations are deficient and not long enough for deciphering the processes controlling this accelerated sea-ice retreat. Thus, high-resolution, longer-term proxy records are needed for reconstruction of natural climate variability. In this context, we applied a biomarker approach on the well-dated sediment core ARA04C/37 recovered in the southern Beaufort Sea directly off the Mackenzie River, an area that is characterized by strong seasonal variability in sea-ice cover, primary productivity and terrigenous (riverine) input. Based on our biomarker records, the Beaufort Sea region was nearly ice-free in summer during the late Deglacial to early Holocene (14 to 8 ka). During the mid-late Holocene (8 to 0 ka), a seasonal sea-ice cover developed, coinciding with a drop in both terrigenous sediment flux and primary production. Supported by multiple proxy records, two major flood events characterized by prominent maxima in sediment flux occurred near 13 and 11 ka. The former is coincident with the Younger Dryas Cooling Event probably triggered by a  freshwater outburst from the Lake Agassiz. The origin of the second (younger) one might represent a second Mackenzie flood event, coinciding with meltwater pulse IB/post-glacial flooding of the shelf and related increased coastal erosion. Here, our interpretation remains a little bit speculative, and further research is needed and also in progress.</p>

scholarly journals On the Potential for Abrupt Arctic Winter Sea Ice Loss

2016 ◽  
Vol 29 (7) ◽  
pp. 2703-2719 ◽  
Author(s):  
S. Bathiany ◽  
D. Notz ◽  
T. Mauritsen ◽  
G. Raedel ◽  
V. Brovkin
Keyword(s):  
Sea Ice ◽  
Surface Albedo ◽  
Climate Models ◽  
Climate Model ◽  
Multiple Steady States ◽  
Cloud Feedbacks ◽  
Ice Coverage ◽  
Threshold Mechanism ◽  
Co2 Levels ◽  
Perennial Ice

Abstract The authors examine the transition from a seasonally ice-covered Arctic to an Arctic Ocean that is sea ice free all year round under increasing atmospheric CO2 levels. It is shown that in comprehensive climate models, such loss of Arctic winter sea ice area is faster than the preceding loss of summer sea ice area for the same rate of warming. In two of the models, several million square kilometers of winter sea ice are lost within only one decade. It is shown that neither surface albedo nor cloud feedbacks can explain the rapid winter ice loss in the climate model MPI-ESM by suppressing both feedbacks in the model. The authors argue that the large sensitivity of winter sea ice area in the models is caused by the asymmetry between melting and freezing: an ice-free summer requires the complete melt of even the thickest sea ice, which is why the perennial ice coverage decreases only gradually as more and more of the thinner ice melts away. In winter, however, sea ice areal coverage remains high as long as sea ice still forms, and then drops to zero wherever the ocean warms sufficiently to no longer form ice during winter. The loss of basinwide Arctic winter sea ice area, however, is still gradual in most models since the threshold mechanism proposed here is reversible and not associated with the existence of multiple steady states. As this occurs in every model analyzed here and is independent of any specific parameterization, it is likely to be relevant in the real world.

Sign in / Sign up

Export Citation Format

Share Document