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

===== 3.4.1.3.3 Drivers =====

There is ''high confidence'' that environmental drivers of Arctic surface water change are diverse and depend on local and regional factors such as permafrost properties and geomorphology (Nitze et al., 2018 <sup>[[#fn:r1498|1498]]</sup> ). Thermokarst lake expansion has been observed in the continuous permafrost of northern Siberia (Smith et al., 2005 <sup>[[#fn:r1499|1499]]</sup> ; Polishchuk et al., 2015 <sup>[[#fn:r1500|1500]]</sup> ) and Alaska (Jones et al., 2011 <sup>[[#fn:r1501|1501]]</sup> ); surface water area reduction has been observed in discontinuous permafrost of central and southern Siberia (Smith et al., 2005 <sup>[[#fn:r1502|1502]]</sup> ; Sharonov et al., 2012 <sup>[[#fn:r1503|1503]]</sup> ), western Canada (Labrecque et al., 2009 <sup>[[#fn:r1504|1504]]</sup> ; Carroll et al., 2011 <sup>[[#fn:r1505|1505]]</sup> ; Lantz and Turner, 2015 <sup>[[#fn:r1506|1506]]</sup> ) and interior Alaska (Chen et al., 2012 <sup>[[#fn:r1507|1507]]</sup> ; Rover et al., 2012 <sup>[[#fn:r1508|1508]]</sup> ). Increased evaporation from warmer/longer summers, decreased recharge due to reductions in snow melt volume, and dynamic processes such as ice-jam flooding (Chen et al., 2012 <sup>[[#fn:r1509|1509]]</sup> ; Bouchard et al., 2013 <sup>[[#fn:r1510|1510]]</sup> ; Jepsen et al., 2015 <sup>[[#fn:r1511|1511]]</sup> ) are important considerations for understanding observed surface water area change across the Arctic.

Satellite and model-derived estimates of evapotranspiration show increases across the Arctic (Rawlins et al., 2010 <sup>[[#fn:r1512|1512]]</sup> ; Liu et al., 2014 <sup>[[#fn:r1513|1513]]</sup> ; Liu et al., 2015b <sup>[[#fn:r1514|1514]]</sup> ; Fujiwara et al., 2016 <sup>[[#fn:r1515|1515]]</sup> ; Suzuki et al., 2018 <sup>[[#fn:r1516|1516]]</sup> ) ( ''medium confidence'' ). Increases in the seasonal active layer thickness impact temporary water storage and thus runoff regimes in drainage basins. Formation of taliks underneath lakes and rivers may result in reconnection of surface with sub-permafrost ground water aquifers with varying hydrological consequences depending on local geological and hydraulic settings (Wellman et al., 2013 <sup>[[#fn:r1517|1517]]</sup> ).

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