finding 26.1 : key-message-26-1

Alaska’s marine fish and wildlife habitats, species distributions, and food webs, all of which are important to Alaska’s residents, are increasingly affected by retreating and thinning arctic summer sea ice, increasing temperatures, and ocean acidification. Continued warming will accelerate related ecosystem alterations in ways that are difficult to predict, making adaptation more challenging (very likely, very high confidence).

This finding is from chapter 26 of Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II.

Process for developing key messages:

The Alaska regional chapter was developed through public input via workshops and teleconferences and review of relevant literature, primarily post 2012. Formal and informal technical discussions and narrative development were conducted by the chapter lead and contributing authors via email exchanges, teleconferences, webinars, in-person meetings, and public meetings. The authors considered inputs and comments submitted by the public, the National Academies of Sciences, Engineering, and Medicine, and federal agencies. The author team also engaged in targeted consultations during multiple exchanges with contributing authors, who provided additional expertise on subsets of the Traceable Account associated with each Key Message.

Description of evidence base:

Changes in arctic sea ice and its impacts on marine ecosystems and various biological resources are well documented by 38 years of satellite records2aa47611-1a24-4796-b0a8-a0ba3092e470 and the scientific literature.13e01b3b-caf8-4d85-ac0f-5689df47762a,da92a0e3-1fab-4616-a181-ed764427b250,379cfaee-cad3-44ac-95b1-8fbb068f4ab3,4533be93-297b-42ce-99d3-898b575d8dee,4aa97ec3-8028-499e-9ef2-9a73eafce4c6,7fbfdebd-eb73-40be-88ec-109ad7a226fd,fbcc5bed-188c-42db-8b6c-f699814f3838 The finding of a continuing retreat of arctic sea ice is supported by sea ice modeling and continued CO2 emissions.61d6757d-3f7a-4e90-add7-b03de796c6c4,6e730a84-66a2-4e74-96cb-c9e6824cf185 The northward distribution of ocean fish species is documented by numerous scientific papers: see Perry et al. (2005),6591e535-9938-4885-9377-0154b655241d Thorsteinson and Love (2016),eb929d72-ab8a-453a-bf91-d32bdd942b87 and Mecklenburg et al. (2002).7c26ef52-3041-49fe-a99a-f597b17c72f6 The impacts of an increased open Arctic sea contributing to increases in ocean acidification32a7c6b7-16ce-49f8-8667-7343d9d40ea9 and expanding deeper into the Arctic Basin3edd9d0c-4aed-49d8-b248-483dcb0dfff0 will need validation with further studies.

New information and remaining uncertainties:

To date, relatively few of Alaska’s marine species have been studied for their response to ocean acidification, and the assessment of potential impacts is challenging due to each species’ differing habitats, life cycle stages, and response and adaptation mechanisms. It is known that some organisms respond more dramatically to environmental change than others, and warming ocean temperatures may be more significant in the short term than ocean acidification. There is significant uncertainty in the projected increase of shipping through the Arctic and the Bering Strait, since much of this increase will be driven by economic factors and not climate or other environmental change.

Assessment of confidence based on evidence:

There is very high confidence that the arctic sea ice will continue to reduce in size over the next 20–40 years, and it is likely that the Arctic Ocean will be nearly ice-free in late summer by mid-century based on current climate models. There is also high confidence that this melting will have an effect on the northward expansion of North Pacific fish species and associated effects on associated food webs. There is very high confidence that continued melting of the Arctic Ocean ice will have an effect on the habitat and behavior of polar bear and walrus. There is high confidence that Alaska’s ocean waters are becoming increasingly acidic. Given this increase, it is very likely that there will be biological impacts, but it is uncertain which species will be affected and to what extent.

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