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

==== 3.2.2.4 Sea Ice Changes ====

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Sea ice is a key driver of polar marine life, hosting unique ecosystems and affecting diverse marine organisms and food webs through its impact on light penetration and supplies of nutrients and organic matter ( [[#Arrigo--2014|Arrigo, 2014]] ). Since the late 1970s, Arctic sea ice area has decreased for all months, with an estimated decrease of 2 million km 2 (or 25%) for summer sea ice (averaged for August, September and October) in 2010–2019 as compared with 1979–1988 (WGI AR6 [[IPCC:Wg2:Chapter:Chapter-9#9.3.1|Section 9.3.1.1]] ; [[#Fox-Kemper--2021|Fox-Kemper et al., 2021]] ). For Antarctic sea ice there is no significant global trend in satellite-observed sea ice area from 1979 to 2020 in either winter or summer, due to regionally opposing trends and large internal variability (WGI AR6 [[IPCC:Wg2:Chapter:Chapter-9#9.3.2|Section 9.3.2.1]] ; [[#Maksym--2019|Maksym, 2019]] ; [[#Fox-Kemper--2021|Fox-Kemper et al., 2021]] ).

CMIP6 simulations project that the Arctic Ocean will ''likely'' become practically sea ice free (area below 1 million km 2 ) for the first time before 2050 and in the seasonal sea ice minimum in each of the four emission scenarios SSP1-1.9, SSP1-2.6, SSP2-4.5 and SSP5-8.5 (Figure 3.7; WGI AR6 [[IPCC:Wg2:Chapter:Chapter-9#9.3.2|Section 9.3.2.2]] ; Notze and SIMIP Community, 2020; [[#Fox-Kemper--2021|Fox-Kemper et al., 2021]] ). Antarctic sea ice area is also projected to decrease during the 21st century, but due to mismatches between model simulations and observations, combined with a lack of understanding of reasons for substantial inter-model spread, there is ''low confidence'' in model projections of future Antarctic sea ice changes, particularly at the regional level (WGI AR6 [[IPCC:Wg2:Chapter:Chapter-9#9.3.2|Section 9.3.2.2]] ; [[#Roach--2020|Roach et al., 2020]] ; [[#Fox-Kemper--2021|Fox-Kemper et al., 2021]] ).

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