Editing IPCC:AR6/SROCC/Chapter-4 (section)

==== 4.2.1.3 Ocean Processes ====

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In general, increasing temperatures lead to a lower density (‘thermal expansion’) and therefore the larger its volume per unit of mass. Thus, warming leads to a higher sea level even when the ocean mass remains constant. Over at least the last 1500 years changes in sea level were related to global mean temperatures (Kopp et al., 2016 <sup>[[#fn:r22|22]]</sup> ), partly because of ice mass loss, and partly because of thermal expansion. Models and observations indicate that over recent decades, more than 90% of the increase in energy in the climate system has been stored in the ocean. Hence, thermal expansion provides insight into climate sensitivity (Church et al., 2013 <sup>[[#fn:r23|23]]</sup> ). Findings from sea level studies and the energy budget are consistent (Otto et al., 2013 <sup>[[#fn:r24|24]]</sup> ). As thermal expansion per degree is dependent on the temperature itself, heat uptake by a warm region has a larger impact on SLR than heat uptake by a cold region. This contributes to regional changes in sea level, which are also caused by the water temperature and salinity variations (e.g., Lowe and Gregory, 2006; Suzuki and Ishii, 2011 <sup>[[#fn:r25|25]]</sup> ; Bouttes et al., 2014 <sup>[[#fn:r26|26]]</sup> ; Saenko et al., 2015 <sup>[[#fn:r27|27]]</sup> ). Regional patterns in sea level change are also modified from the global average by oceanic and atmospheric (fluid) dynamics (Griffies and Greatbatch, 2012 <sup>[[#fn:r28|28]]</sup> ), including trends in ocean currents, redistribution of temperature and salinity (sea water density), buoyancy, and atmospheric pressure. An analysis of these trends in Coupled Model Intercomparison Project Phase 5 (CMIP5) General Circulation Models (GCMs; Yin, 2012) demonstrates the potential for &gt;15 cm of SLR by 2100 and &gt;30 cm by 2300 (RCP8.5) along the east coast of the USA and Canada from fluid dynamical processes alone. However, Coupled Model Intercomparison Project Phase 6 (CMIP6) GCM simulations are not yet available for an updated analysis of these processes in SROCC.

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