Kodiak Daily Mirror - As Arctic warms NOAA increases effort to update Alaska sea charts
As Arctic warms, NOAA increases effort to update Alaska sea charts
by James Brooks / editor@kodiakdailymirror.com
Sep 16, 2011 | 83 views | 0 0 comments | 2 2 recommendations | email to a friend | print
NOAA ship Fairweather rests alongside the cargo pier at Coast Guard base Kodiak on Tuesday, Sept. 13, 2011. The ship has just completed an extended mapping mission in Kotzebue Sound, off Alaska's northwest Coast.
(James Brooks photo)
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KODIAK — In 1826, Kodiak was already a bustling settlement as Capt. Frederick W. Beechey sailed the H.M.S Blossom along the Bering Strait on a mission to chart its waters for the Royal Navy.

His crew used a lead line, a piece of rope with a heavy object on the end, to measure the water’s depth.

They drew their own charts, scrawling shoals with a quill pen.

Today, almost two centuries later, mariners use those exact measurements to navigate the waters of Kotzebue Sound in Alaska’s far north. Countless tides, storms and waves have changed the shoreline and seabed, but the numbers have remained.

The crew of the National Oceanic and Atmospheric Administration ship Fairweather are on a mission to fix that.

One of three NOAA ships dedicated to hydrographic surveying — the first step in creating charts — the Fairweather has spent its summer in Alaska, chipping away at old data and creating new charts for the 21st century.

In addition to its mission off Kotzebue on Alaska’s northwest coast, the Fairweather has been working around Spruce Island. Measurements there date from the 1920s, when the lead line was still the height of technology and the great 1964 Alaska earthquake hadn’t shifted the earth.

“Most of the area that we’re charting in Alaska, a lot of it hasn’t been measured since the 1800s,” said Dawn Forsythe, a spokeswoman for the NOAA Office of Coast Survey, which manages the Fairweather and her sister ships, converting their data into physical charts.

Even for the federal government, that’s slow work.

“We’re responsible for 3.5 million square nautical miles,” Forsythe said. NOAA funding currently allows for mapping only 2,500 square nautical miles per year. “At the current rate, it would be like 500 years (to update it all).”

Because of that sheer size, NOAA has to prioritize its updates. Places with a lot of ship traffic, like port entrances, get first priority. So do places with a shifting ocean bottom, like the Gulf of Mexico.

“In some parts of the Gulf (of Mexico), we might come back every couple of years because of the hurricanes,” Forsythe said.

As the Arctic sea ice retreats and people rush north in search of oil and seafood, Alaska sea lanes are becoming more crowded and more important. A 500,000-ton oil platform can’t be placed using a chart from the 1800s.

In 2010, NOAA completed its Arctic Strategy and Vision plan, a strategy for how the organization will address the changing Arctic. It declared: “Most of the shoreline along Alaska’s northern and western coasts has not been mapped since 1960, if ever, and confidence in the nautical charts of the region is extremely low.”

In 2010, the Fairweather sailed the Bering Strait, mapping the sea around Little Diomede and Big Diomede, a pair of islands that straddle the International Date Line and the Russia-U.S. maritime boundary.

This year, the NOAA ship split its time between Kodiak and Kotzebue. Capt. David Neander, commander of the Fairweather, said budget problems in Washington fouled its schedule.

“On a normal year, we’ll get 190 to 200 days a year, which means we’ll have a spring project, a summer project and a fall project. Each one of those projects lasts on average two, two-and-a-half months. This year we had a one-month project off Kodiak and (the Kotzebue project).”

NOAA had scheduled six mapping projects in Alaska this year: Kotzebue, the mouth of the Kuskokwim River, the Krenitzin Islands at the eastern end of the Aleutians, the north coast of Kodiak Island, Chatham Strait in Southeast Alaska, and Prince of Wales Island, also in Southeast.

The Rainier, NOAA’s other Pacific Ocean mapping ship, was scheduled do some of that work, but an overhaul lasted longer than expected, and the ship is only now leaving drydock.

All that means demand for the Fairweather’s services is high. NOAA’s survey priorities map of Alaska looks like an explosion in a paint factory, with red signifying the most critical needs and other shades fading to a fluorescent green that dominates Prince William Sound, signifying full coverage.

A large portion of the waters southwest of Kodiak Island and hugging the northern coast is striped red and white. NOAA wanted to declare those a critical concern, Neander said, but was told it couldn’t add any more critical areas. Instead, they’re simply “emerging critical.”

“There are some longer-term projects scheduled for all around Kodiak Island to update the charts,” he said, but what the ship has already done is impressive. “We found some fairly significant differences between what was on the chart and what we found.”

In the area north of Spruce Island, for example, the Fairweather found a half-dozen variations requiring special notices to mariners.

“If we find it, we send it out as soon as we can,” he said.

In one example, “We found a three-foot sounding in the middle of a bay that was shaded at five fathoms,” Neander said.

The Fairweather does most of its work with a pair of active sonar. One, mounted on the bottom of the ship’s hull, provides accurate depth data, shooting many beams of sound per second to the seafloor. The sound bounces back at different rates, signifying variations in the surface.

A second sonar, called side-scan sonar, is in a torpedo-shaped body towed behind the ship. That sonar covers a wider area but doesn’t provide accurate depth data. It’s used primarily in areas with a sandy, flat bottom. It can confirm an area is level, while the ship’s primary sonar measures what that level is.

“So if we saw something stick up out there, we’d see it in the side-scan, then run it over with the depth data,” Neander said.

While the side-scan is useful in places like Kotzebue Sound, where the seafloor is flat, off Kodiak the seafloor is jagged and rocky, meaning the ship has to make more scanning passes.

The Fairweather does have four small boats with their own sonar, and those can be used in shallow bays and places where the Fairweather itself can’t go.

“Woody Island Channel would be something we could do if we were tied up for an extended period of time. We could run boats from downtown (Kodiak),” Neander said.

Aboard the ship, measurements are adjusted for tides, waves and other factors. The sonar beams themselves must be steered and altered for changing ocean conditions that can reflect the sound waves.

“We push the buttons and the computer processes, but knowing when to cast is another thing,” said NOAA Corps Ens. Steven Loy, a Fairweather officer.

All that work generates tremendous amounts of data. Lt. Caryn Zacharias, another officer onboard the Fairweather, said one day of work can generate a gigabyte of information. A whole mapping project can mean 500 GB. Alaska’s mapping projects this year alone would be 2.5 terabytes, equivalent to 2,500 copies of the Encyclopedia Britannica.

And the ship is only one part of the mapping process.

NOAA must fly shoreline surveys, charting the coast at high tide and low, then tie that in with measurements from the Fairweather. The data is processed at the NOAA office in Seattle, the branch that handles Pacific Ocean data.

“We have technicians there who do nothing but check and double check the soundings and tides,” Forsythe said. “Everything is checked for depths and precision.”

Once the technicians have their way with the data, the cartographers take over, transforming the processed information into a visual chart.

The whole process can take a year or more, which means the Fairweather’s measurements from this summer could start reaching sailors by next June.

Only then can they shelve Capt. Beechey’s maps where they belong — with the history books.

Contact Mirror editor James Brooks at editor@kodiak


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