Scientists sample the Chukchi and Beaufort seas for effects of climate warming
The NOAA research vessel Ocean Starr tied up at the port causeway last weekend, one in a parade of vessels carrying ocean scientists and their tools to document effects of climate warming and loss of sea ice on the Arctic marine ecosystem.
Fisheries research scientist Ed Farley and his team stopped at Nome following a three-week research cruise of the Chukchi and Beaufort seas where they worked the waters for an extensive look at midwater fishes as well as the food web and physical environment in that part of the Arctic.
“We’re trying to understand what is happening within the water column, the changes that may be occurring as we’re starting to see these big shifts in seasonal ice in terms of the loss of sea ice and the warming of the water column,” Farley explained.
Farley is a program manager at the Ecosystem Monitoring and Assessment Program at Alaska Fisheries Science Center laboratory in Juneau.
The team has performed sampling at 32 stations 30 nautical miles apart and completed 27 midwater trawl tows for samples to be examined, weighed, measured and recorded in the Ocean Starr’s onboard lab. The survey area lies between latitudes 70°N and 72.5°N on the Chukchi Sea shelf.
At each station the team is collecting information on zooplankton, the prey of fish and birds.
The scientists’ integrated study looks at the ecosystem through the lenses of physical oceanography—temperature and dissolved oxygen, the abundance of zooplankton and larval fish for analysis in the shipboard laboratory to find out what is going on with distribution of sea life and changes in the lowest elements of the food chain; they looked at midwater fishes. Arctic cod less than a year old dominated the midwater catch.
“We captured large numbers of Arctic sand lance within the midwater tows which constituted a significant percentage of the catch abundance in the western portion of the survey area,” said Farley. “That was new to us, in this northern region. This isn’t the first time we’ve been out here.”
The program has performed the integrated study four times—2012, 2013, 2017 and 2019. Arctic sand lance were not found in large numbers in 2017, and were typically only caught south of Cape Lisburne.
“The only thing I’m seeing that is really different than what we saw in the past is this northern extension of age zero walleye pollock,” he said. “I was surprised to see just how big they were in the nearshore area.”
They are conducting benthic trawls—sampling invertebrates as snails, small snow crab, and brittle stars as well as small fishes in the bottom.
Benthic? That’s anything associated with the bottom of a body of water.
“As usual for bottom trawls in this area, invertebrates dominated the catches, providing 97 percent of catch weight and only 3 percent was fish,” Farley said in a report to colleagues on the second leg of the survey.
The team took bottom grabs to examine the surface of the ocean floor. They collected mud samples, which they dumped out and sorted through in the lab, examining and recording everything in it.
Farley showed a large freezer in the lab that held hundreds of small fish and other specimens that will go to the Auk Bay Laboratory for further study.
The team uses a fine sieve apparatus—a bongo net, which looks like what? A couple of bongo drums. The net takes and strains the water column at mid-depths for plankton samples. They sampled fish for harmful algal blooms.
The scientists also use an apparatus called a CTD, an instrument that measures conductivity, temperature and depth (for pressure) of seawater. The gadget has a carousel of bottles, called Niskin bottles, which may be opened and shut by push button for sampling water at desired depths.
The scientists found very warm temperatures at the bottom and on the surface of the Chukchi in the survey area. Surface areas across the shelf varied from 5.3°C to 10.9°C, or 41.5° F to 51.6°F.
“Wow, that’s way up. In this region, in the Chukchi, that’s astounding,” Farley said. “We didn’t want that.”
Bottom temperatures including all stations ranged from negative 1.6°C to 7.7°C, or 29.12°F to 45.9°F. The warmest surface and bottom temperatures were recorded inshore near Icy Cape.
The next leg of the survey voyage has taken the team to the Southern Chukchi Sea where they will sample for juvenile salmon.
It is likely the rapidly warming Arctic region will continue to surprise and astound members of the science community who are trying to understand what is happening with the ecosystem. While the recession of the sea ice has not reached or exceeded the lower limits of record season 2012, it is getting close. This week, anecdotal reports from Kaktovik say the weather is in the high 50°s F; the trailing edge of the sea ice is 800 miles north of Savoonga, St. Lawrence Island, and 400 miles north of Utqiagvik (formerly Barrow).
The work is part of the Arctic Integrated Ecosystem Survey Aug. 23 to Sept. 19.
Farley’s current research is focused on addressing hypotheses that link climate change and variability to ecosystem function and to link ecosystem function to fish growth, fitness, and survival at critical life history stages.
There will be a final report on findings following conclusion of the final voyage of the survey and additional analysis.