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

==== 3.2.1.3 Ocean Circulation ====

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The major elements of Southern Ocean circulation are assessed in Cross-Chapter Box 7 in Chapter 3; Arctic Ocean circulation is considered here. Arctic processes, such as discharge of freshwater from the Greenland Ice Sheet, have the potential to impact on the formation of the headwaters of the Atlantic Meridional Overturning Circulation (Section 6.7.1), and can impact on the structure and function of the marine ecosystem with implications for commercially-harvested species (Sections 3.2.3, 3.2.4).

Satellite data indicate a general strengthening of the surface geostrophic currents in the Arctic basin (Armitage et al., 2017 <sup>[[#fn:r324|324]]</sup> ). Between 2003 and 2014, the strength of some currents in the Beaufort Gyre approximately doubled (Armitage et al., 2017 <sup>[[#fn:r323|323]]</sup> ). Over 2001–2014, annual Bering Strait volume transport from the Pacific to the Arctic Ocean increased from 0.7×10 6 m 3 s –1 to 1.2×10 6 m 3 s –1 (Woodgate et al., 2015 <sup>[[#fn:r325|325]]</sup> ). Mesoscale eddies are characterised by horizontal scales of ~10 km in the Arctic, and are important components of the ocean system. Increased wind power input to the Arctic Ocean system can in principle be compensated by the production of eddy kinetic energy; analysis of observations in the Beaufort Gyre region suggest this is ''about as likely as not'' (Meneghello et al., 2017 <sup>[[#fn:r326|326]]</sup> ). Data of sufficiently high resolution is limited in the boundary regions of the Arctic Ocean, precluding estimates of eddy variability on a basin-wide scale. In the central basin regions, a statistically significant higher concentration of eddies was sampled in the Canadian Basin compared to the Eurasian Basin between 2003 and 2014; further, a medium correspondence was found between eddy activity in the Beaufort Gyre region and intensified gyre flow (Zhao et al., 2014 <sup>[[#fn:r327|327]]</sup> ; Zhao et al., 2016 <sup>[[#fn:r328|328]]</sup> ).

In contrast to the Southern Ocean (Cross-Chapter Box 7 in Chapter 3), there is comparatively little knowledge on changing Arctic frontal positions and current cores since AR5. An exception is that the Beaufort Gyre expanded to the northwest between 2003 and 2014, contemporaneous with changes in its freshwater accumulation and alterations in wind forcing, resulting in increased proximity to the Chukchi Plateau and Mendeleev Ridge (Armitage et al., 2017 <sup>[[#fn:r329|329]]</sup> ; Regan et al., 2019 <sup>[[#fn:r330|330]]</sup> ) (Section 3.2.1.2.2).

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