scholarly journals Review of manuscript by Merz et al. entitled “Warm Greenland during the last interglacial: the role of regional changes in sea ice cover”.

2016 ◽  
Author(s):  
Pepijn Bakker
Keyword(s):  
Sea Ice ◽  
Ice Cover ◽  
Last Interglacial

scholarly journals Warm Greenland during the last interglacial: the role of regional changes in sea ice cover

2016 ◽  
Vol 12 (10) ◽  
pp. 2011-2031 ◽  
Author(s):  
Niklaus Merz ◽  
Andreas Born ◽  
Christoph C. Raible ◽  
Thomas F. Stocker
Keyword(s):  
Sea Ice ◽  
Ice Cover ◽  
Labrador Sea ◽  
Last Interglacial ◽  
Atlantic Sector ◽  
Nordic Seas ◽  
Proxy Records ◽  
Ice Retreat ◽  
Sea Ice Retreat

Abstract. The last interglacial, also known as the Eemian, is characterized by warmer than present conditions at high latitudes. This is implied by various Eemian proxy records as well as by climate model simulations, though the models mostly underestimate the warming with respect to proxies. Simulations of Eemian surface air temperatures (SAT) in the Northern Hemisphere extratropics further show large variations between different climate models, and it has been hypothesized that this model spread relates to diverse representations of the Eemian sea ice cover. Here we use versions 3 and 4 of the Community Climate System Model (CCSM3 and CCSM4) to highlight the crucial role of sea ice and sea surface temperatures changes for the Eemian climate, in particular in the North Atlantic sector and in Greenland. A substantial reduction in sea ice cover results in an amplified atmospheric warming and thus a better agreement with Eemian proxy records. Sensitivity experiments with idealized lower boundary conditions reveal that warming over Greenland is mostly due to a sea ice retreat in the Nordic Seas. In contrast, sea ice changes in the Labrador Sea have a limited local impact. Changes in sea ice cover in either region are transferred to the overlying atmosphere through anomalous surface energy fluxes. The large-scale spread of the warming resulting from a Nordic Seas sea ice retreat is mostly explained by anomalous heat advection rather than by radiation or condensation processes. In addition, the sea ice perturbations lead to changes in the hydrological cycle. Our results consequently imply that both temperature and snow accumulation records from Greenland ice cores are sensitive to sea ice changes in the Nordic Seas but insensitive to sea ice changes in the Labrador Sea. Moreover, the simulations suggest that the uncertainty in the Eemian sea ice cover accounts for 1.6 °C of the Eemian warming at the NEEM ice core site. The estimated Eemian warming of 5 °C above present day based on the NEEM δ15N record can be reconstructed by the CCSM4 model for the scenario of a substantial sea ice retreat in the Nordic Seas combined with a reduced Greenland ice sheet.

scholarly journals Warm Greenland during the last interglacial: the role of regional changes in sea ice cover

2016 ◽  
Author(s):  
Niklaus Merz ◽  
Andreas Born ◽  
Christoph C. Raible ◽  
Thomas F. Stocker
Keyword(s):  
Sea Ice ◽  
Ice Cover ◽  
Labrador Sea ◽  
Last Interglacial ◽  
Atlantic Sector ◽  
Climate System Model ◽  
Nordic Seas ◽  
Ice Retreat ◽  
Sea Ice Retreat

Abstract. The last interglacial, the Eemian, is characterized by warmer than present conditions at high latitudes and is therefore often considered as a possible analogue for the climate in the near future. Simulations of Eemian surface air temperatures (SAT) in the Northern Hemisphere, however, show large variations between different climate models and it has been hypothesized that this model spread relates to diverse representations of the Eemian sea ice cover. Here we use versions 3 and 4 of the Community Climate System Model (CCSM3 and CCSM4), to highlight the crucial role of sea ice and sea surface temperatures during the Eemian, in particular for SAT in the North Atlantic sector and in Greenland. A substantial reduction in sea ice cover results in an amplified atmospheric warming and, thus, a better agreement with Eemian proxy records. Sensitivity experiments with idealized lower boundary conditions reveal that warming over Greenland is mostly due to a sea ice retreat in the Nordic Seas. In contrast, sea ice changes in the Labrador Sea have a limited local impact. Changes in sea ice cover in either region are transferred to the overlying atmosphere through anomalous surface energy fluxes. The large-scale warming simulated for the sea ice retreat in the Nordic Seas further relates to anomalous heat advection. Diabatic processes play a secondary role, yet distinct changes in the hydrological cycle are possible. Our results imply that temperature and accumulation records from Greenland ice cores are sensitive to sea ice changes in the Nordic Seas but insensitive to sea ice changes in the Labrador Sea. Moreover, our simulations suggest that the uncertainty in the Eemian sea ice cover accounts for 1.6 °C of the Eemian warming at the NEEM ice core site. The estimated Eemian warming of 5 °C above present-day based on the NEEM δ15N record can be reconstructed by the CCSM4 model for the scenario of a substantial sea ice retreat in the Nordic Seas combined with a reduced Greenland ice sheet.

scholarly journals Sustaining observations in the polar oceans

2014 ◽  
Vol 372 (2025) ◽  
pp. 20130337 ◽  
Author(s):  
E. P. Abrahamsen
Keyword(s):  
Sea Ice ◽  
Ocean Circulation ◽  
Ice Cover ◽  
Global Ocean ◽  
Shelf Seas ◽  
Polar Oceans ◽  
Global Ocean Circulation ◽  
Coordination And Collaboration ◽  
Temperature Depth

Polar oceans present a unique set of challenges to sustained observations. Sea ice cover restricts navigation for ships and autonomous measurement platforms alike, and icebergs present a hazard to instruments deployed in the upper ocean and in shelf seas. However, the important role of the poles in the global ocean circulation provides ample justification for sustained observations in these regions, both to monitor the rapid changes taking place, and to better understand climate processes in these traditionally poorly sampled areas. In the past, the vast majority of polar measurements took place in the summer. In recent years, novel techniques such as miniature CTD (conductivity–temperature–depth) tags carried by seals have provided an explosion in year-round measurements in areas largely inaccessible to ships, and, as ice avoidance is added to autonomous profiling floats and gliders, these promise to provide further enhancements to observing systems. In addition, remote sensing provides vital information about changes taking place in sea ice cover at both poles. To make these observations sustainable into the future, improved international coordination and collaboration is necessary to gain optimum utilization of observing networks.

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.

scholarly journals Simulating the Last Interglacial Greenland stable water isotope peak: The role of Arctic sea ice changes

2018 ◽  
Vol 198 ◽  
pp. 1-14 ◽  
Author(s):  
Irene Malmierca-Vallet ◽  
Louise C. Sime ◽  
Julia C. Tindall ◽  
Emilie Capron ◽  
Paul J. Valdes ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Sea Ice ◽  
Last Interglacial ◽  
Isotope Peak ◽  
Arctic Sea ◽  
Water Isotope

Arctic MIZ Sensitivity to Atmosphere- Ice-Ocean Feedbacks

2021 ◽  
Author(s):  
Rebecca Frew ◽  
Daniel Feltham ◽  
David Schroeder ◽  
Adam Bateson
Keyword(s):  
Sea Ice ◽  
Mixed Layer ◽  
Thickness Distribution ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
Atmospheric Conditions ◽  
Arctic Sea ◽  
Atmospheric Forcings ◽  
The Impact

<p><span>Over the past few decades, as the summer Arctic sea ice cover has been shrinking, the marginal ice zone (MIZ) has been widening. Projections indicate that the majority of the sea ice cover will become marginal (here defined as that region with ice area fractions between 0.15 and 0.8) over the next few decades. The impact of the change in atmospheric forcings on the sea ice cover and MIZ between the 1980s and the 2010s is evaluated using a coupled sea ice (CICE)-mixed layer model, that includes a prognostic floe size-thickness distribution (FSD) model. As the MIZ accounts for a greater fraction of the sea ice cover, some feedbacks with the atmosphere and ocean are expected to strengthen. The role of sea ice feedbacks with the atmosphere and ocean in response to the change in atmospheric conditions between the 1980s to the 2010s are evaluated using feedback denial simulations. In particular: i) the albedo feedback; ii) feedbacks associated with changes to mixed layer stratification (including changes in mixed layer properties) and therefore the ocean heat flux to the sea ice; and iii) changes to the lateral melt rate due to decreasing floe sizes.</span> </p>

scholarly journals Arctic Ocean sea ice cover during the penultimate glacial and the last interglacial

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Ruediger Stein ◽  
Kirsten Fahl ◽  
Paul Gierz ◽  
Frank Niessen ◽  
Gerrit Lohmann
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Ice Cover ◽  
Last Interglacial

The impact of orbital forcing on the Arctic climate during the Last Interglacial simulated by the IPSL-CM6A-LR model

2020 ◽  
Author(s):  
Marie Sicard ◽  
Masa Kageyama ◽  
Pascale Braconnot ◽  
Sylvie Charbit
Keyword(s):  
Solar Radiation ◽  
Sea Ice ◽  
Arctic Sea Ice ◽  
Arctic Climate ◽  
The Arctic ◽  
Orbital Forcing ◽  
Last Interglacial ◽  
Arctic Sea ◽  
The Impact

<p>The Last Interglacial (129 – 116 ka BP) is a time period with a strong orbital forcing which leads to a different seasonal and latitudinal distribution of insolation compared to the present. In particular, these changes amplify the Arctic climate seasonality. They induce warmer summers and colder winters in the high latitudes of the Northern Hemisphere. Such surface conditions favour a huge retreat of the arctic sea ice cover.<br>In this study, we try to understand how this solar radiation anomaly spreads through the surface and impacts the seasonal arctic sea ice. Using IPSL-CM6A-LR model outputs, we decompose the surface energy budget to identify the role of atmospheric and oceanic key processes beyond 60°N and its changes compared to pre-industrial. We show that solar radiation anomaly is greatly reduced when it reaches the Earth’s surface, which emphasizes the role of clouds and water vapor transport.<br>The results are also compared to other PMIP4-CMIP6 model simulations. We would like to thank PMIP participants for producing and making available their model outputs.</p>

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