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

===== 3.4.3.1.2 Observed vertical redistributions =====

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Epipelagic isotherms have recently (1980–2015) deepened at an average of 6.6 ± 18.8 m per decade ( [[#Pinsky--2019|Pinsky et al., 2019]] ), but there is ''low agreement'' on whether species move deeper in pursuit of thermal refuge. Prior studies suggested range shifts to depth ( [[#Dulvy--2008|Dulvy et al., 2008]] ; [[#Pinsky--2013|Pinsky et al., 2013]] ; [[#Yemane--2014|Yemane et al., 2014]] ), but increasing evidence suggests that fish and planktonic communities across large parts of the North Atlantic, sub-Arctic and northeast Pacific Ocean redistribute horizontally with horizontal climate velocity, except where vertical temperature gradients are particularly steep. There is ''low confidence'' for temperature-driven depth shifts in the epipelagic zone ( [[#Burrows--2019|Burrows et al., 2019]] ; [[#Campana--2020|Campana et al., 2020]] ; [[#Caves--2021|Caves and Johnsen, 2021]] ). At the same time, decreasing oxygen concentrations and the vertical expansion of OMZs have already decreased suitable habitat of pelagic fishes, including tuna and billfishes, by ~15% primarily due to vertical compression of environmental niches ( [[#Stramma--2012|Stramma et al., 2012]] ; [[#Deutsch--2015|Deutsch et al., 2015]] ).

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