Editing IPCC:AR6/SR15/Chapter-3 (section)

== 3.5.4.1 Arctic sea ice ==

<div id="section-3-5-4-1-block-1"></div>

Ice-free Arctic Ocean summers are ''very likely'' at levels of global warming higher than 2°C (Notz and Stroeve, 2016; Rosenblum and Eisenman, 2016; Screen and Williamson, 2017; Niederdrenk and Notz, 2018) <sup>[[#fn:r1169|1169]]</sup> . Some studies even indicate that the entire Arctic Ocean summer period will become ice free under 2°C of global warming, whilst others more conservatively estimate this probability to be in the order of 50% (Section 3.3.8; Sanderson et al., 2017) <sup>[[#fn:r1170|1170]]</sup> . The probability of an ice-free Arctic in September at 1.5°C of global warming is low and substantially lower than for the case of 2°C of global warming ( ''high confidence'' ) (Section 3.3.8; Screen and Williamson, 2017; Jahn, 2018; Niederdrenk and Notz, 2018) <sup>[[#fn:r1171|1171]]</sup> . There is, however, a single study that questions the validity of the 1.5°C threshold in terms of maintaining summer Arctic Ocean sea ice (Niederdrenk and Notz, 2018) <sup>[[#fn:r1172|1172]]</sup> . In contrast to summer, little ice is projected to be lost during winter for either 1.5°C or 2°C of global warming ( ''medium confidence'' ) (Niederdrenk and Notz, 2018) <sup>[[#fn:r1173|1173]]</sup> . The losses in sea ice at 1.5°C and 2°C of warming will result in habitat losses for organisms such as seals, polar bears, whales and sea birds (e.g., Larsen et al., 2014) <sup>[[#fn:r1174|1174]]</sup> . There is ''high agreement'' and ''robust evidence'' that photosynthetic species will change because of sea ice retreat and related changes in temperature and radiation (Section 3.4.4.7), and this is ''very likely'' to benefit fisheries productivity in the Northern Hemisphere spring bloom system (Section 3.4.4.7).

<div id="section-3-5-4-2"></div>

<span id="arctic-land-regions"></span>