A more normal winter has helped to dispel a warm water patch in the North Pacific, but it hasn’t disappeared entirely.
The warm patch, nicknamed “the blob,” has been documented since fall 2013, when abnormally warm weather across the North Pacific led to changes in ocean conditions, potentially affecting marine life. Alaska has seen warmer winters with less snow for the past three years.
This year, though, temperatures fell back into the more normal range in Southcentral Alaska and around most of the state, according to climate records. Homer had to postpone its annual winter king salmon fishing tournament due to excessive ice in the harbors, and Anchorage saw some of its coldest temperatures since 1999. Skiers on the Kenai Peninsula had much more of a chance to get out this year, with plenty of long-lasting snowpack on the ground since December.
In fact, most of Southcentral’s weather stations registered below average temperatures this winter, said National Oceanic and Atmospheric Administration climatologist Rick Thoman.
“Sea surface temperatures in the Gulf of Alaksa have dropped back to pretty close to normal,” he said. “… If you look in the upper part of the ocean, there is still some area … where there is a slight warm anomaly. That is still there.”
The North Slope registered significantly above average temperatures this winter, while most of the state’s Interior and Southeast was about average, he said. Similarly, precipitation varied; though Anchorage and the lower-elevation parts of the Kenai Peninsula have seen above-average snow, snowfall is fairly low in the Matanuska-Susitna Valley and at higher elevations, like in Turnagain Pass.
The cooler winter has lowered the sea’s surface temperature, which in turn helps to reduce the overall temperature of the blob, though that takes time, said Kris Holderied, director of the NOAA Kasitsna Bay Laboratory on Kachemak Bay. The ocean temperatures are colder closer to the coasts, but further offshore, it takes longer for the temperature to change, she said. Through its monitoring programs, NOAA found that the blob permeated the ocean’s surface down to about 1,000 feet, she said.
“You can guess that it’s going to take awhile for all of that to cool off,” she said.
It’s hard to say exactly what the causes of the extra-warm water are, but Alaskans have been reporting wildlife die-offs in the last several years. In late 2015, Homer residents started spotting sick and dying sea otters on the beaches of Kachemak Bay; in January 2016, U.S. Fish and Wildlife Service biologists began looking into the large numbers of dead common murres that washed up on shores all along the west coast of the U.S., from California to Alaska. In summer 2016, dismal returns of pink salmon triggered commercial fishing closures in management areas all across the Gulf of Alaska and led to a federal disaster declaration in March 2017.
Each case likely had different causes — the murres, for example, were clearly starving, while some of the otters looked well-fed and showed signs of Strep Syndrome, a bacterial infection — but the ocean is the common factor between them. For the otters, the warm water conditions in 2015 coincided with a prevalence of harmful algal blooms in Kachemak Bay. The algal blooms cause toxins to accumulate in filter-feeding animals like mussels and clams, which otters feed on, said Kachemak Bay National Estuarine Research Reserve research director Angie Doroff in an email.
“The relationship between warm water events and sea otter mortality are not fully understood but a link via bioaccumulated toxins in their prey may play a role,” she wrote.
Surveys in 2012 estimated the otter population in Kachemak Bay at about 5,900 animals, but the estimate is preliminary and several years old. Researchers are planning another in summer 2017, she wrote. The reserve is also conducting a research project on native clams in the bay, as clam populations have been documented in decline, and including sea otter foraging studies because clams are a favorite prey item for otters, she wrote.
When the coastal conditions change, it could affect the basis of the food web for marine animals that feed on small animals and plankton that come from the coasts. NOAA researchers are conducting regular plankton studies in Kachemak Bay to see how changing ocean conditions are affecting the marine food web, Holderied said.
“As you’re closer to the coast here, like Kachemak Bay, we can see it cooling off relative to what it has been the last couple of winters,” she said. “It’s still not as cold as it can be, but it’s getting there.”
One thing that’s clear is that the El Nino weather pattern didn’t cause the blob to form — it began forming on its own before the warmer weather kicked in, Thoman said. While the cooler winter has helped, there may be other confounding factors, such as increased snowmelt from rivers in Southeast Alaska flowing out into the gulf. The freshwater can create an insulating layer for the warmer water beneath, he said.
“That’s one of the reasons that I would expect we’ll see some hint of that blob persist, and depending how the fall works out, that warmer water could (continue),” he said.
Outside the tropics, weather usually drives the ocean rather than vice versa, Thoman said. However, after several years of persistent warmer weather, the ocean can form a sort of memory, he said.
“If we persist and get that warmth down to depth, that becomes memory in the system,” he said. “What’s being driven can change based on the duration of the weather.”
Reach Elizabeth Earl at firstname.lastname@example.org.