Ocean Climate Change Headlines from the 2010 Alaska Marine Science Symposium
| Marilyn Sigman, Alaska SeaGrant/MAP
Tags: Climate Change, Bering Sea, Changing Alaska Marine Ecosystems, Changing Arctic Sea Ice, Changes in Ocean Current Systems, Ocean Acidification, Humpback Whales, Herring
The evidence of climate change presented for Alaska's seas at the 2010 AMSS included effects of both warmer years than on average and colder years than on average as well as evidence that different areas and species will respond differently to climate change.
Third Cold Year in a Row Drives the Bering Sea Ecosystem
Mike Sigler and Rodger Harvey summarized the findings of the team of scientists after field seasons during three cold years in a “Headlines” presentation:
- Cold winter and spring temperatures resulted again in a delay in sea ice melt and a sustained “cool pool” of water over the Continental Shelf into the summer after the ice melted.
- One of main hypotheses of the ecosystem study is that physics structures the trophic relations. Several aspects typical of a cold year pattern supported this hypothesis. Large Calanus spp. zooplankton were abundant during the spring while pollock were not abundant during the summer because the “cool pool” limited the extent of their spawning habitat suitable for pollock and also for cod. Scientists had predicted that most of the productivity under the extensive ice and near the ice edge would end up on the bottom to fuel the benthic community and were surprised at the amount of cycling of nutrients and carbon in the water column which they traced to activity of microzooplankton.
- Based on data from 2000-2005, juvenile pollock have lower overwinter survival during warm years and the water column is more stable during warm summers which also lowers pollock survival because nutrients are not recycled back into the upper water column.
- Seabirds foraged further and switched their prey in relation to the availability of prey compared to that in 2008, but fur seals did not.
- Based on their study of differences between the ice and water temperature regimes of the northern and southern Bering Sea, the physical oceanographers are now predicting that the northern Bering Sea will continue to sustain arctic conditions (cold water, long periods of darkness, sea ice cover) even if the Arctic Ocean warms. Another major hypothesis of the study is that “place matters,” and fish species are already moving northward in response warming seas to the south, so the persistence of these Arctic conditions has major implications.
- Surveys of Bering Sea community members are demonstrating that subsistence harvests have already shifted in relation to prey location and availability. Predicted changes in commercial fishing harvests are being modeled.
Headlines for 2010
- 2010 will be the fourth and final field season for the Bering Sea Ecosystem Study. Another cold year could continue the existing pattern or the El Nino weather pattern could provide a warm, or warmer, year to help the scientists test and refine their hypotheses and models.
The Polar Icescape has Changed
- Sea ice scientists observed polar ice that was more extensive than the maximum retreat that occurred in 2007, but also the smallest percentage of ice older than two years old on record. Areas mapped as multi-year ice during the interpretation of remote sensing images turned out, upon field observation, to be new ice or slushy, rotten ice; which would further reduce the actual amount of multi-year ice compared to the estimate.
- Late freeze-ups of sea ice in November continued, changing the overall ice regime in different ways for ice-dependent and ice-associated than for the migratory cetaceans. (Moran 2010, Eicken et. al., 2010; Moore et. al., 2010)
- Walrus used terrestrial haul-outs in the Chukchi Sea in 2007, when some 3,000 went ashore, and again in lower numbers in 2009. (Funk et. al., 2010)
- Gray whales are staying longer along the Arctic Coast and feeding in the Barrow “hot spot” as bowhead whales into November on krill. (In 2004, some gray whales remained throughout the winter.) (Moore et. al., 2010)
The Alaska Coastal Current has Strengthened and Freshened Significantly
Based on an analysis of annual chemical signatures in coralline red algae, the Alaska Coastal Current has freshened to a degree unprecedented in at least the previous 65 years which is likely a result of accelerated glacial melt. The ACC has also increased in strength. (Chan et. al., 2010)
Alaska’s Seas are Pre-conditioned to Become More Acidic Soon
Alaska's seas are especially vulnerable to rapidly-increasing acidification as a result of the storage of carbon from anthropogenic activities in the ocean due to the combination of cold water (with a higher storage capacity than warm water), highly-productive ecosystems that re-mineralize carbon in large amounts on a seasonal basis, and upwelling processes onto the Continental Shelf and inshore. Corrosive waters, which are undersaturated with aragonite, were documented at the surface in the Gulf of Alaska, Bering Sea, and Arctic Ocean during fall, 2009. (Mathis 2010)
Other Alaska marine research news: Humpback Whales have Winter Feasts on Herring in Prince William Sound
A series of studies and modeling by a team of nine scientists concluded that humpback whale predation on herring during the winter in Prince William Sound is taking a high percentage of the biomass that would have otherwise been available for commercial fishing on a sustainable basis and may be preventing the recovery of the population.
Abstracts from Symposium presentations and posters are available online.