Story by Leone Thierman
This image of sea surface
temperature (in C) is based on output from a simulation
of the northern Gulf of Alaska SALMON model by Kate
Hedstrom. A visualization was created by Bill Brody,
ARSC Visualization Research Specialist, showing seasonal
warming and cooling.
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NORTHERN GULF OF ALASKA OCEAN FORECAST
SEA-AIR-LAND MODELING AND OBSERVING NETWORK
UNIVERSITY OF ALASKA FAIRBANKS
330 PM AST TUE JUL 1X 200X
TONIGHT…With fresh water runoff steadily rising, the 33
PSU isoline is moving deep offshore along the Northern Gulf Alaska.
Salinity is at 32.5 and surface temperatures are 18 C with light
bergy bits coming off Columbia Glacier. Fronts that move through the ocean affect water conditions and
marine life as intensely as weather fronts affect atmospheric conditions
above the water. Just like weather forecasting, predicting ocean
circulation conditions can offer a distinct advantage to the people
who live and work along the coastal waters of Alaska. Oceanographic
researchers, fisherman and others operating ocean vessels working
in the northern Gulf of Alaska will one day have real-time forecasts
that detail conditions in the marine environment beneath the sea
surface, as well as above it.
An ocean predictive system of this kind could allow marine biologists
to estimate fluctuations in fish, bird and marine mammal populations.
In turn, the system could assist in determining where, when and
how sea harvesting should be permitted. Advance knowledge of sea
surface currents could assist in search and rescue operations,
as well as in establishing response protocols and clean-up operations
for hazardous materials and oil spill dissemination.
To help make these possibilities a reality, the Sea-Air-Land
Modeling and Observing Network (SALMON) Project at the University
of Alaska Fairbanks (UAF) is combining observational data and computer
modeling to provide a coastal ocean forecasting system that can
help predict the variability of the Alaska marine ecosystem. As
part of this effort, ARSC’s oceanographic researcher, Kate
Hedstrom, is creating an oceanic and ecosystem-coupled model using
ARSC’s supercomputers.
The highlighted area
shows the coastal waters of the northern Gulf of Alaska
incorporated in the Hedstrom SALMON project computer
model.
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The area of the SALMON Project model stretches along the northern
Gulf of Alaska, from Kayak Island in the east to the Shumagin Islands
west of Kodiak, including Prince William Sound, Cook Inlet and
the outer coast of Kodiak. The computer-modeled output is compared
to real-time temperature, salinity, current and wind data gathered
from this region. This model output is also compared to information
on the many variables that affect the marine ecosystem, such as
nutrients, phytoplankton and zooplankton. These data are collected
through the use of various scientific instruments placed strategically
throughout the northern Gulf of Alaska, including oceanographic
buoys, meteorological stations and high- frequency radar sites.
Satellites located above the sound also contribute to the information
gathering process. Advanced Very High Resolution Radiometer (AVHRR)
data from around the world are received at stations in Gilmore
Creek, Alaska and Wallops Island, Virginia. These stations then
send the data to the National Oceanic and Atmospheric Administration
(NOAA) and the National Environmental Satellite, Data, and Information
Service (NESDIS) in Suitland, Maryland where the data are processed
and archived.
Collected data alone does not give the entire picture, and satellite
imagery only provides data for conditions from the sea surface
upwards. To initiate and implement the desired forecasting network,
scientists must combine the massive amounts of data collected on
ocean currents with data gathered on atmospheric and marine conditions
and incorporate all of it into a three-dimensional model. Insight
and predictive capabilities are gained with the use of a 3D-modeled
hypothesis. Thus, linking the observational component of this research
with modeling activities can help scientists explain the past,
the present and a projected future for the entire ecosystem.
Hedstrom uses the Regional Ocean Modeling System (ROMS) numerical
model for her simulation. Its efficient parallel algorithms provide
the ability to easily include tides, vertical mixing, atmospheric
forcing and freshwater inflow that are related to the northern
Gulf of Alaska. ROMS, in development by teams at UCLA and Rutgers
University, is particularly suited to simulate the coastal ocean
weather of the Coastal Gulf of Alaska (CGOA), as it can be used
to study both the complexities of the coastal ocean and large-scale
ocean currents that interact with the Alaska Coastal Current (ACC). |
