The goal of the AOOS ecosystem/climate trends component is to build upon and leverage existing activities to develop an integrated network of physical, chemical and biological observations off Alaska to meet short- and long-term needs. Alaska has a need to understand marine climate variability and ecosystem change in the long term, as well as how conditions affect ocean circulation and productivity in the short term. Because of Alaska’s remoteness and the high cost of ship time, consortia are forming to maintain support of long-term time series of physical, biological and chemical oceanographic conditions to understand climate variability and ecosystem change.
Long times-series are required for scientists to tease out pattern (and cause) from simple year-to-year variability. Like other regions, the Northern Pacific undergoes significant inter-annual variability, driven partially by variations in major climatic indices (e.g. El Niños, the Pacific Decadal Oscillation). Larger longer-term variations referred to as “regime shifts” have occurred in the past, and will likely occur again. Regime shifts are expressed as fundamental shifts in ecosystem structure and function, such as the 1976 regime shift that resulted in a switch within the Gulf of Alaska from a shrimp-dominated fishery to one dominated by pollock, salmon and halibut. Given the potential for such profound climatic impact, the Seward Line Long-term Observation Program (http://www.sfos.uaf.edu/sewardline/) provides critical observations on the current state of the Northern Gulf of Alaska ecosystem, and a basis for understanding the mechanisms responsible for such changes.
The Seward Line represents the most comprehensive long-term multidisciplinary sampling program in the Coastal Gulf of Alaska that allows observation of changes in the oceanography of this region that is critical to Alaska’s fisheries, subsistence and tourist economies. Seward Line observations over the past 19 years have fundamentally revised our understanding of the coastal Gulf of Alaska ecosystem and allow us an appreciation of its major properties, and inter-annual variability. To date, we have observed both unusually warm and cold years, which influence the timing of the planktonic communities, but not necessarily their ultimate abundance and biomass. The quantity and composition of both late spring and summer zooplankton, appear to be significantly correlated with PWS hatchery Pink Salmon survival in this region; relationships to herring have yet to be fully explored. Thus, springtime abundance of zooplankton along the Seward Line appears to be an index of generally favorable years for higher trophic levels throughout the Gulf of Alaska. The Seward Line and associated projects are providing an oceanographic foundation to explore broader regional patterns as well as searching for relationships between oceanography and other species of forage and commercial fish.
Time series datasets. AOOS will partner with others to maintain long time series in the Gulf of Alaska, Bering Sea, and Chukchi/Beaufort Seas and to ensure that data from the sampling efforts are accessible to all researchers and the public, as well as marine spatial planning efforts. AOOS will contribute to a consortium led by UAF SFOS to support sampling along the Seward Line, the longest multidisciplinary time series in Alaska. The line provides a critical long-term data series on oceanographic conditions in the GOA and how the region may be changing with climate impacts. It has been sampled continuously since October 1997, with some measurements going back to late 1970’s. Funding supports the cost of two cruises a year (May and September), sample/data processing and analysis.
- Support ship transects along the Seward Line twice per year. Sampling activities will:
- Determine thermohaline, velocity, and nutrient structure of the Seward Line across the Gulf of Alaska shelf, and at stations throughout Prince William Sound.
- Determine phytoplankton biomass distribution, and estimate primary production.
- Determine the distribution, abundance and biomass of zooplankton.
- Support determination of Carbonate Chemistry (i.e. Ocean Acidification)
- Provide at-sea experience for graduate students within the UAF system