In world of thinning ice, Arctic scientists view life and death

MONICA SOUTHWORTH

July 24, 2008 at 2:22PM AKST

A gray whale getting bludgeoned to death by orcas. Sea ice receding. The Arctic Ocean sucking up Pacific waters.

The seas off Alaska are an eventful place, found scientists from a Japanese oceanographic research vessel who recounted their research season at the Museum of the Aleutians on July 17.

During a five-week cruise through the Chukchi Sea, the scientists noted significant decline in sea ice coverage, collected algae and viewed a killer whale attack.

The scientists from Hokkaido University stopped on their way home to Japan to give a talk about their research on July 17 at the Museum of the Aleutians.

During its cruise, the Oshoro Maru traveled north to the Chukchi Sea, undertaking several projects. Four researchers presented their research and results from the 2007 cruise.

The first focused on sea ice and organisms, such as algae, that grow on the ice. The researchers took samples of plankton, benthos (organisms such as crab and sea urchins) and other items gathered from the bottom of the sea as the ship traveled north.

A second project, performed by Kohei Mizobata and K. Shimada from the Tokyo University of Marine Science and Technology, focused on Arctic sea ice reduction and warm Pacific water.

“The summer Pacific water triggers a sea ice reduction in the Arctic,” Mizobata said.

“In August 2007, we had the highest water temperature off the Alaska coast.”

Mizobata said that scientists need better measures for heat in the Bering Sea.

Currently researchers use satellite image and a single snapshot of temperature taken during the annual summer cruise. For the temperature index, Mizobata uses a data set from a University of Washington mooring buoy and uses a model to predict the temperatures year-round.

The result marked 2007 as an unusual year.

“We had a much higher heat flux, but we’re not sure about this year yet,” said Mizobata, who will have to wait until returning to Tokyo to analyze data collected on this cruise.

The third talk, given by Jia Wang, focuses on the Arctic dipole anomaly. Wang works for the National Oceanic and Atmospheric Administration in Ann Arbor, Mich. His work looks at heat flux changes beginning in 2000. The Oshoro Maru has been conducting these cruises for the past 15 years, but Wang only showed data sets back to 2000.

“In 2007 we recorded a record low sea-ice extent,” Wang said.

In a graph Wang showed during the presentation, there was a negative correlation between sea ice coverage and time.

Wang also showed the differences in sea-level pressure and changes that causes. If there is a lower pressure in the Arctic, water from the Pacific will be drawn into the Arctic. This will cause ice on the Pacific side of the Arctic Ocean to melt more quickly than the sea ice on the Atlantic side. He continued to explain the pressure and temperature difference causes the Arctic Ocean to “suck up” the warmer Pacific water.

Wang said that the dipole anomaly is an atmospheric movement causing ice to move from the Pacific side of the Arctic to the Atlantic side. The Arctic oscillation is the differences in sea level pressure, which causes water to move from one body of water to another, but is much more long term.

The dipole anomaly is considered to be more dominant because it is seasonal and the effects of it are much more visible during a short period of time.  

When the anomaly is positive, the pressure flows from the Pacific side of the Arctic Ocean to the Atlantic side, moving ice out of the Arctic Basin and towards the Nordic Seas. When the anomaly is negative, the ice flows from the Atlantic side of the Arctic to the Pacific, because of a stronger gyre in the Beaufort Sea.

The short-term effect of the anomaly is a seasonal driving of sea ice away, and the indirect long-term affect is that the Arctic Ocean will “suck up” warmer water that will increase its temperature.

The fourth talk at the museum was about cetaceans, an animal group that includes whales, dolphins and porpoises, in the Chukchi Sea.

“The most exciting part of the trip for me was seeing the killer whale attack,” Keiko Sekiguchi, a cetacean biologist at the Pacific Aquaculture and Coastal Resources Center at the University of Hawaii at Hilo.

Sekiguchi showed several pictures of killer whales attacking a gray whale. One picture showed the gray whale’s head coming out of the water with a noticeable stream of blood mixed with water coming out of its mouth.

Several of the pictures showed the killer whales attacking the gray whale by hitting it, possibly with their heads, but all that could be seen were large splashes of water mixed with blood from the whale. Sekiguchi said that some of the splashes they were seeing were larger than those of humpback whales.

“There were no wounds on the outside, the killer whales hit their prey,” Sekiguchi said.

“The whale was bleeding internally.”

Sekiguchi concluded by saying that marine mammals are moving farther north.

“You have to actively search for the whales,” Sekiguchi explained.

The two locations for looking for whales on the Oshoro Maru were the bridge and the upper deck. During bad weather, the lookout would stay in the bridge, but there was a better view from the upper deck.

Sekiguchi was excited to see her first bowhead whale on the cruise. The sighting was due in part to having all the right equipment searching for whales.

“And the most important and cheapest piece of equipment is the graduate student,” Sekiguchi said with a laugh.