Editing IPCC:AR6/SROCC/Chapter-3 (section)

===== 3.2.1.1.3 Seasonality =====

There is ''high confidence'' that the Arctic sea ice melt season has extended by 3 days per decade since 1979 due earlier melt onset, and 7 days per decade due to later freeze-up (Stroeve and Notz, 2018 <sup>[[#fn:r122|122]]</sup> ). This longer melt season is consistent with the observed loss of sea ice extent and thickness (Sections 3.2.1.1.1; 3.2.1.1.2). While the melt onset trends are smaller, they play a large role in the earlier development of open water (Stroeve et al., 2012b <sup>[[#fn:r123|123]]</sup> ; Serreze et al., 2016 <sup>[[#fn:r124|124]]</sup> ) and melt pond development (Perovich and Polashenski, 2012 <sup>[[#fn:r125|125]]</sup> ) which enhance the sea ice albedo feedback (Stroeve et al., 2014b <sup>[[#fn:r126|126]]</sup> ; Liu et al., 2015a <sup>[[#fn:r127|127]]</sup> ). Observed reductions in the duration of seasonal sea ice cover are reflected in community-based observations of decreased length of time in which activities can safely take place on sea ice (Laidler et al., 2010 <sup>[[#fn:r128|128]]</sup> ; Eisner et al., 2013 <sup>[[#fn:r129|129]]</sup> ; Fall et al., 2013 <sup>[[#fn:r130|130]]</sup> ; Ignatowski and Rosales, 2013 <sup>[[#fn:r131|131]]</sup> ).

Changes in the duration of Antarctic sea ice cover over 1979–2011 largely followed the spatial pattern of sea ice extent trends with reduced ice cover duration in the Amundsen/Bellingshausen Sea region in summer and autumn owing to earlier retreat and later advance, and increases in the Ross Sea due to later ice retreat and earlier advance (Stammerjohn et al., 2012 <sup>[[#fn:r132|132]]</sup> ).

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