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Casey J. Wall, Tsubasa Kohyama, and Dennis L. Hartmann

1. Introduction Sea ice, low clouds, and the atmospheric boundary layer modulate the climate of the Southern Ocean by influencing surface heat fluxes. During winter, sea ice insulates the ocean from the cold atmosphere above, reducing the rate of ocean heat loss at the surface by a factor of 10 to 100 ( Gordon 1991 ). Low clouds and moisture emit longwave (LW) radiation downward and heat the surface, and low-level winds control the surface turbulent heat and moisture fluxes. When sea ice forms

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Jan Sedláček, Reto Knutti, Olivia Martius, and Urs Beyerle

1. Introduction The Arctic sea ice area and thickness have been decreasing steadily over the last few decades ( Maslanik et al. 2007 ; Nghiem et al. 2007 ; Serreze et al. 2007 ; Comiso et al. 2008 ). Serreze et al. (2007) reported that the decrease occurred throughout the year. However, the summer months experienced a larger decrease than the winter months. During summer 2007 the Arctic sea ice area was reduced substantially. The minimum sea ice area in September was 28% lower than the

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Ana C. Ordoñez, Cecilia M. Bitz, and Edward Blanchard-Wrigglesworth

1. Introduction Sea ice predictability studies have focused mainly on the Arctic or Antarctic, with few comparative studies of Arctic and Antarctic differences, especially at the regional scale. Johnson et al. (1985) is the only paper to the authors’ knowledge that makes comparisons of predictability between the pan-Arctic and pan-Antarctic and among their subdivided regions, but their study relies on observational data from a short time period and considers only a limited set of sea ice

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James Williams, Bruno Tremblay, Robert Newton, and Richard Allard

1. Introduction There has been a negative trend in the Arctic Ocean sea ice extent since the late 1970s, when satellite observations became available on a consistent basis ( Parkinson et al. 1999 ). This trend is present in all months and ranges from −0.30 to −0.87 × 10 6 km 2 decade −1 (from −2.3% to −13.6% decade −1 ) in May and September, respectively ( Fetterer et al. 2002 , updated daily). The rate of decline in the September minimum sea ice extent (SIE) accelerated in recent decades

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Yuyan Li and Zhicong Yin

1. Introduction Since the beginning of the satellite-observed sea ice era, record-breaking minimum values of sea ice cover have been observed in 2007 and 2012 ( Polyakov et al. 2017 ), which might be connected to the trends of sea level pressure (SLP) in Arctic in summer ( Simmonds 2015 ). The dramatic reduction of the summer Arctic sea ice (ASI) extent in recent years has fundamentally changed the nature of the ice ( Maslanik et al. 2011 ) including the trend of thinning ( Kwok and Rothrock

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Erica Rosenblum and Ian Eisenman

several CMIP phases as comprehensive climate models have continued to be developed. The two most recent phases have been phase 3 (CMIP3; Meehl et al. 2007 ) and phase 5 (CMIP5; Taylor et al. 2012 ), which were used to project future climate change in the Intergovernmental Panel on Climate Change (IPCC) Fourth and Fifth Assessment Reports (AR4 and AR5), respectively. The historical simulations have shown substantial bias in reproducing Arctic sea ice changes during the satellite record, with the

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Michael Sigmond and John C. Fyfe

1. Introduction Antarctic sea ice extent (SIE) has increased by about 1% decade −1 since the introduction of reliable (satellite based) measurements in 1979 (e.g., Turner et al. 2013 ) and reached its highest observed value in September 2013 ( Fetterer et al. 2009 ). The question of why Antarctic sea ice has increased in a warming world represents one of the most fundamental unsolved mysteries in polar climate science. Previous studies have suggested a number of possible explanations

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Michael E. Kelleher, Blanca Ayarzagüena, and James A. Screen

, the pattern of influence has an AO-like structure with an anomalous center at high latitudes. The AO has also been linked to Arctic sea ice cover changes due to its influence on high-latitude temperature and wind. Rigor et al. (2002) found the winds associated with the positive AO phase cause a wind-driven movement of sea ice, which map onto one of the main Arctic sea ice circulation regimes presented in Proshutinsky and Johnson (1997) . The AO induces anomalous sea ice motion and therefore

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Matthieu Chevallier, David Salas y Mélia, Aurore Voldoire, Michel Déqué, and Gilles Garric

1. Introduction Within the last few years, the shrinking summer Arctic sea ice cover has awakened interest in obtaining seasonal outlooks of the sea ice cover. Such outlooks are intended to give valuable information, for example, on marine accessibility of maritime routes or on the duration of the ice-free season in the marginal ice zones. Only a few institutions produce sea ice predictions using a coupled atmosphere–ocean general circulation model (AOGCM), although such models are becoming the

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Mitchell Bushuk, Xiaosong Yang, Michael Winton, Rym Msadek, Matthew Harrison, Anthony Rosati, and Rich Gudgel

seasonal sea ice predictions in the Barents Sea. The sea ice cover in the Barents Sea is a dominant contributor to winter Arctic sea ice variability and trends ( Cavalieri and Parkinson 2012 ) and influences local economic activity such as fisheries, shipping, and natural resource industries ( Jung et al. 2016 ). These factors have motivated a need for accurate seasonal sea ice predictions in this region. A number of recent studies, using both statistical methods ( Schlichtholz 2011 ; Onarheim et al

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