Future physical and chemical changes to the ocean are likely to significantly affect the distribution and productivity of many marine species. Tuna are of particular importance in the tropical Pacific, as they contribute significantly to the livelihoods, food and economic security of island states. Changes in water properties and circulation will impact on tuna larval dispersal, preferred habitat distributions and the trophic systems that support tuna populations throughout the region. Using recent observations and ocean projections from the CMIP3 and preliminary results from CMIP5 climate models, we document the projected changes to ocean temperature, salinity, stratification and circulation most relevant to distributions of tuna. Under a business-as-usual emission scenario, projections indicate a surface intensified warming in the upper 400 m and a large expansion of the western Pacific Warm Pool, with most surface waters of the central and western equatorial Pacific reaching temperatures warmer than 29 °C by 2100. These changes are likely to alter the preferred habitat of tuna, based on present-day thermal tolerances, and in turn the distribution of spawning and foraging grounds. Large-scale shoaling of the mixed layer and increases in stratification are expected to impact nutrient provision to the biologically active layer, with flow-on trophic effects on the micronekton. Several oceanic currents are projected to change, including a strengthened upper equatorial undercurrent, which could modify the supply of bioavailable iron to the eastern Pacific.

Item Type:	Refereed Article
Keywords:	climate change, tuna, Pacific Ocean
Research Division:	Earth Sciences
Research Group:	Oceanography
Research Field:	Biological oceanography
Objective Division:	Environmental Policy, Climate Change and Natural Hazards
Objective Group:	Understanding climate change
Objective Field:	Effects of climate change on the South Pacific (excl. Australia and New Zealand) (excl. social impacts)
UTAS Author:	Graham, FS (Dr Felicity McCormack)
ID Code:	102460
Year Published:	2013
Web of Science® Times Cited:	30
Deposited By:	IMAS Research and Education Centre
Deposited On:	2015-08-21
Last Modified:	2017-11-01
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