Seward Line Oceanography: Summer on the Tiglax Series

Compiled from online sources by: Debra Corbett | Nanutset Heritage

The first scientific expedition of the year for the USFWS M/V Tiglax supports the Seward Line Oceanography project, a long-term observation program begun in 1998-2004 by GLOBEC.  The project continued from 2005-2009 by the North Pacific Research Board (NPRB), and is now funded by NPRB, Alaska Ocean Observation System and Exxon Valdez Oil Spill, and managed through UAF’s Institute of Marine Science.  Cruises are conducted twice a year in spring (May) and late summer (early September).

The Gulf of Alaska (GOA) supports a diverse ecosystem that includes several commercially important fishes, as well as culturally and economically important mammals and plants.  Historic observations suggest a connection between the GOA ecosystems and climate variations that range from interannual to interdecadal; the specific mechanisms by which climate variation causes ecosystem changes, however, are poorly understood.  Sampling along the Seward line, from Resurrection Bay south to the outer continental shelf, is producing a multi-year data set that will lead to a better understanding of the seasonal cycle and the variability that occurs from year to year in environmental conditions and biological productivity in the Gulf of Alaska.

Seward Line

During seasonal sampling projects, data about the Seward line are collected about a variety of environmental and biological conditions from salinity and temperature to plankton. The physical environment is assessed using electronic device that measures Conductivity, Temperature and Depth (CTD) at high resolution in real-time. Additional sensors measure water clarity, plant pigment in the water, light is available for plant growth, and/or how much oxygen is dissolved in the water (DO).  The biological environment is sampled by capturing zooplankton for analysis.  Krill and other larger and faster zooplankton are captured at night using a sophisticated “Multinet” system which allows separation of the upper 100m of the ocean into 5 layers, each 20m thick.

The Seward Line is the most detailed multi-disciplinary long-term oceanographic sampling program in the northern Gulf of Alaska. The Seward Line work coordinates with other projects that focus on Cook Inlet and Kachemak Bay, the Alaska Coastal Current, Prince William Sound, and still more broadly across the Gulf of Alaska. The Seward Line monitoring shows that the GOA shelf undergoes alternating periods of warm and cold springs, each of which lasts for multiple years.

For more information about the Seward Line Oceanography project and results visit:



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