An anomaly or the new norm, researchers are carefully tracking the persistent warm water blob in the northeast Pacific Ocean and what it means for salmon.
In the last two months, a high pressure ridge that developed over B.C.’s coastal area resulted in an extended warm summer. The storm season was late, and the water is two to three degrees warmer.
Richard Dewey, associate director of science at Ocean Networks Canada, and the University of Victoria, has been carefully tracking the approximately 2,000-kilometre unseasonably warm area that made its first appearance in fall of 2013 and became much more noticeable in spring of 2014 — when researchers coined the term “the blob”.
“That event woke us up to what is happening here. The atmosphere, storm and jet streams come together and we get weaker winds over the gulf and therefore we don’t mix up the cold water and things remain warm,” Dewey said.
Now they’re paying attention. By 2017, oceanographers were starting to see the warm mass dissipate at depth, but this year it’s back in the northeast Pacific and in the Bering Sea.
“Maybe this is the trend. Maybe this is how climate change is going to reflect itself in our backyard, but we don’t quite know that yet,” Dewey said.
Ocean Networks Canada has instruments along the bottom and near the shore of the ocean. They didn’t pick up the 2014 blob on their sensor until months later, so researchers are keeping a close eye on satellite data and sea surface temperature maps for the Gulf of Alaska.
Impacts on salmon
Ocean warming is affecting fresh water temperatures as well.
Sue Grant is leading Fisheries and Oceans Canada’s (DFO) State of the Salmon Program. Her role is to integrate what we know about salmon and their ecosystems. Oceanographers and fresh water researchers are seeing a co-relation between the blob and the warming in rivers and streams.
“The blob itself is an oceanographic phenomenon but it’s caused by a coupling with the atmosphere and that also has repercussions in fresh water,” Grant said.
Salmon are anadromous, with fresh water and marine life stages, and they’re experiencing warmer temperatures in both habitats. Grant said the effects of the 2014 and 2015 warm blob vary across the salmon stocks in B.C. and Yukon territory.
“Responses are mixed, although some of our southern stocks and some of our northern ones weren’t doing so well this year. We were seeing lower than average survivals in salmon stocks in the Fraser Watershed last year across the different species and we were seeing below average survivals again this year in the Fraser. There are other examples up north,” she said.
Grant uses a marathon analogy to describe what the 3-5 degree Celsius above-season temperatures are doing to salmon.
If she were to run a marathon in 50 degrees Celsius she may not survive because 50-60 degrees Celsius is outside her optimal temperature range. Salmon have an optimal temperature range as well, and when they’re trying to migrate upstream during the summer run it can have a negative affect on their migration.
Warmer-than-average water temperatures are also impacting the level of nutrients.
When the ecosystem shifted in 2014-2015, the surface layer of the Gulf of Alaska was weaker in nutrients. Ocean Networks Canada saw that cold-water species requiring a nutrient-rich environment weren’t as prevalent, while warm-water species that could adapt to low-nutrient conditions tended to dominate.
“When the salmon are out there in the gulf and along the coast feeding under those conditions they came back in 2016-17, a little smaller than usual,” Dewey said.
“The numbers I have seen say these warm conditions can result in smaller fish sizes so that has some impact as well.”
Both Grant and Dewey say they’re paying attention but it’s far too early to make projections and what the 2018 warm blob means for salmon.
They can, however, take the data from the past few years — salmon responses to the warming in fresh water and marine ecosystems — and watch to see if there’s a pattern and what that could mean for the future of salmon stocks.