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James W. Hurrell, James J. Hack, Dennis Shea, Julie M. Caron, and James Rosinski

.0) was released in June 2004, and the release included complete collections of component model source code, documentation, and input data, as well as model output from several experiments. The purpose of this note is to document the global sea surface temperature (SST) and sea ice concentration (SIC) boundary dataset that has been developed specifically for uncoupled simulations with present and future versions of CAM. Perhaps the most important field in climate system modeling is SST. A significant

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Ryan Eastman and Stephen G. Warren

1. Introduction Arctic climate has changed dramatically in the past two decades. End-of-summer sea ice extent has declined and reached surprisingly small values in 2007 and 2008 ( Stroeve et al. 2008 ; Comiso et al. 2008 ). Shrinking ice cover has been accompanied by an increase in surface air temperature (SAT) of almost 0.5°C decade −1 from 1979 through 2003, as observed by the International Arctic Buoy Programme ( Rigor et al. 2000 ). Clouds are thought to have an important role in the

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Zhaomin Wang, John Turner, Yang Wu, and Chengyan Liu

1. Introduction During 2014–16 Antarctic sea ice retreated at an unprecedented rate with total sea ice extent (SIE) reaching a record low level in spring 2016 ( Fig. 1 ). This was unexpected, as there had been a small but significant upward trend in total Antarctic SIE since 1978 ( Comiso and Nishio 2008 ; Turner et al. 2009 ; Parkinson and Cavalieri 2012 ), with record high daily extents being observed in September 2012 ( Turner et al. 2013 ), 2013 ( Reid et al. 2015 ), and 2014 ( Fetterer

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Zhuo Wang, John Walsh, Sarah Szymborski, and Melinda Peng

1. Introduction The recent decrease of Arctic sea ice coverage is one of the most striking indicators of global environmental change. The Arctic sea ice extent in September, as assessed from satellite observations, has changed significantly, with the pan-Arctic extent in each of the past 13 Septembers (2007–19) all lower than in any years of the earlier satellite era (1979–2006; NSIDC 2018 ). The Arctic is expected to become essentially ice-free during summer by about midcentury ( Notz and

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Jake Aylmer, David Ferreira, and Daniel Feltham

1. Introduction Sea ice is a major component of the climate system, influencing it through its enhanced surface reflectivity compared to the ocean, insulation of the oceans, and role in the thermohaline circulation (e.g., Barry et al. 1993 ). Current and projected loss of Arctic sea ice affects the climate on the global scale, mediated via changes to the atmosphere and ocean circulation ( Budikova 2009 ; Vihma 2014 ; Tomas et al. 2016 ). Antarctic sea ice variability is linked to large

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Uma S. Bhatt, Donald A. Walker, Martha K. Raynolds, Josefino C. Comiso, Howard E. Epstein, Gensuo Jia, Rudiger Gens, Jorge E. Pinzon, Compton J. Tucker, Craig E. Tweedie, and Patrick J. Webber

1. Introduction Arctic land surface temperatures have increased ( Kaufman et al. 2009 ) and are predicted to continue warming with major repercussions for terrestrial ecosystems ( ACIA 2004 ; Serreze et al. 2007 ; Post et al. 2009 ). Observational studies have documented the well-known cooling effect that sea ice has on adjacent landmasses ( Rouse 1991 ; Haugen and Brown 1980 ), whereas global climate model simulations show that coastal Arctic land surfaces warm when summer sea

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Hiroshi Sumata, Frank Kauker, Michael Karcher, and Rüdiger Gerdes

1. Introduction Sea ice is one of the most distinctive features of the Arctic climate system. Although sea ice forms on a thin solid layer of a few meters thick, it substantially modulates heat, freshwater, and momentum exchanges between the atmosphere and the ocean ( Wadhams 2002 ; McPhee 2008 ; Thomas and Dieckmann 2009 ). Improvement of dynamic and thermodynamic processes in sea ice models thus constitutes an important part of climate modeling and a prerequisite for meaningful predictions

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A. Levermann, J. Mignot, S. Nawrath, and S. Rahmstorf

buoyancy flux because of their impact on deep-water formation. Saenko et al. (2004) examine the role of northern sea ice cover for the overturning circulation during global warming experiments by altering the thermal diffusion coefficient in their atmospheric energy–moisture balance model, thereby producing varying temperature and sea ice extent in northern high latitudes. Their main conclusion is that the initial climate around the subpolar gyre is crucial for understanding the weakening of the THC

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Zheng Liu and Axel Schweiger

1. Introduction How atmosphere and sea ice interact depends on the prevailing weather, which can be characterized by the synoptic condition. Stramler et al. (2011) report that during the wintertime of the Surface Heat Budget of the Arctic (SHEBA) field campaign ( Uttal et al. 2002 ), there were two preferred states of surface and atmospheric conditions with distinct signatures in the surface net longwave radiative fluxes: a warm and opaquely cloudy state with low surface pressure, and a cold

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Keith M. Hines, David H. Bromwich, Lesheng Bai, Cecilia M. Bitz, Jordan G. Powers, and Kevin W. Manning

1. Introduction Sea ice, which provides a layer of thermal insulation between the ocean and atmosphere and reflects most of the incident solar insolation, is central to polar climate studies (e.g., Vihma 2014 ). During the twentieth century, Southern Hemisphere sea ice was characterized by large seasonal variations in areal coverage of relatively thin ice surrounding the Antarctic continent, while much of the Northern Hemisphere’s sea ice was thicker multiyear ice in the Arctic Ocean that was

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