Archive for the ‘Alaska’ Tag
by Ensign Sarah Chappel, NOAA Ship Rainier
NOAA Ship Rainier recently surveyed Whale Passage, which separates Whale Island from Kodiak Island, Alaska. The area has never been surveyed with modern full bottom coverage methods, and some project areas were last surveyed by lead lines around a hundred years ago. The area frequently experiences 7 knot currents, making rocky or shoal areas particularly treacherous. Whale Passage is a high traffic area for fishing vessels, U.S. Coast Guard cutters, barges, ferries, and small boats, which is why updating the area’s nautical charts is so important.
Strong currents push around Ilkognak Rock daymark at the entrance of Whale Passage. (Photo by LTJG Damian Manda)
The dynamics of the passage and surrounding area create several challenges for the hydrographic survey teams. The local tidal and current models are not well-known. To resolve this, Rainier was instructed to install four tide gauges in the greater project area, compared to a typical requirement for one gauge. Two of these gauges are a mere 4.5 nautical miles apart, in and just outside of Whale Passage itself. Some areas are so narrow and experience such high currents that it is only possible to survey in one direction in order to maintain control of the launch. The coxswain must plan each turn carefully, to avoid being pushed into dangerous areas. Ideally, these areas would be surveyed at or near slack tide. However, the slack in this survey area is incredibly brief and the predicted slack periods did not match what survey crews saw in the field.
The bathymetry is so dynamic that, even in relatively deep water, boat crews must remain alert for rocks and shoals. The survey teams found several large rocks in locations significantly different from where they were charted. Furthermore, the presence of large kelp beds increases the difficulty of surveying: they can foul the propellers on the launches, add noise to the sonar data, and can also obscure the presence of rocks.
While the work within Whale Passage, and the neighboring Afognak Strait on the north side of Whale Island, is challenging, it is also high-value. In addition to correcting the positions of known rocks and hazards, Rainier and her crew found a sunken vessel. Most importantly, though, they found areas that were charted twice as deep as they actually are. When the chart reads 8 fathoms (48 feet) and the actual depth is only 4 fathoms (24 feet), commercial traffic utilizing the passage could be in serious danger of running aground. Thus far, Rainier has submitted two DTON (danger to navigation) reports for depths significantly shoaler than charted. These new depths are already published on the latest version of chart 16594.
Rainier‘s multibeam sonar data shows a sunken fishing vessel in the vicinity of Whale Passage.
NOAA Ship Rainier will continue to survey the vicinity of Whale Passage, as well as the waters near Cold Bay out in the Alaskan Peninsula, for the remainder of the survey season before heading home to Newport, Oregon.
NOAA Ship Rainier recovers a survey launch after a morning of surveying and data collection. (Photo by LTJG Damian Manda)
–By Christy Fandel, Coast Survey physical scientist
Have you ever wondered what lies beneath the charted soundings on a nautical chart? While surveying Alaskan waters during the 2013 hydrographic field season, collecting bathymetry to update NOAA’s nautical charts, hydrographers revealed many interesting geologic features on the seafloor.
NOAA focuses a significant portion of our ocean mapping effort along the Alaskan coast. The Alaskan coastline represents over 50% of the United States coastline and dated nautical charts are inadequate for the increasing vessel traffic in this region. NOAA surveys are essential for providing reliable charts to the area’s commercial shippers, passenger vessels, and fishing fleets.
This past season, NOAA-funded hydrographic surveys in Alaska revealed many interesting geological features on the seafloor. Three surveys, in particular, took place in southeastern Alaska in the Behm Canal, along the Aleutian Chain within the coastal waters surrounding Akutan Island, and around Chirikof Island.
These three areas were among the areas surveyed by the NOAA Ship Rainier and surveying contractor Fugro-Pelagos during the 2013 field season.
In May, hydrographic surveying conducted by NOAA Ship Rainier in the Behm Canal revealed two distinct geological features. In the northern region of the canal, scientists identified a long, meandering ancient river. This ancient submarine river is nearly 40 km in length with up to 50 m in relief. Further south, Rainier surveyed a large volcanic-like feature. The surveyed volcano appears to have a distinct caldera, or collapse-feature that most likely formed after the volcanic eruption.
Multibeam bathymetry of the northeastern portion of the Behm Canal shows a large, meandering submarine river. The cross-sectional inset highlights the relief of the channel, nearly 50 m, as shown by the red box.
Multibeam data acquired by NOAA Ship Rainier shows a large volcanic feature in the southern portion of the Behm Canal.
Directly following the Behm Canal survey, Rainier transited west to survey the coastal waters surrounding Chirikof Island. The acquired bathymetric data revealed a stark northeast-trending fault in the southeastern portion of the survey area. This surveyed fault is distinguished by a clear misalignment across the fracture.
The red box outlines the northeast-trending fault along the coast of Chirikof Island, shown with bathymetry acquired by the Rainier.
Concurrently, an Office of Coast Survey hydrographic surveying contractor – Fugro-Pelagos – was surveying off the western coast of Akutan Island. Fugro’s hydrographers identified a large volcanic feature within the acquired bathymetric data. The surveyed volcanic feature is believed to be either a volcanic vent or cinder cone volcano. The multiple circular rings outlining this feature may represent the successive lava flows that formed the volcano.
Multibeam bathymetry acquired by Fugro, around Akutan Island, shows a large volcanic vent or cinder cone volcano, marked by multiple circular rings that represent the successive lava flows that formed the volcano.
With the upcoming 2014 hydrographic field season quickly approaching, the number of geologic discoveries will only increase. Extending all along the Aleutian Chain, from Kodiak Island to Bechevin Bay, the planned surveys for the 2014 field season will surely reveal many interesting and previously unknown geologic features.
Cold Bay Elementary School students visit the NOAA Ship Rainier
On September 13, NOAA Ship Rainier began surveying Cold Bay, its fourth project of the summer. Cold Bay is a small town on the Aleutian Peninsula approximately 540 miles southwest of Anchorage, Alaska. The town currently has approximately 88 full-time residents and boasts an airport with one of the longest runways in Alaska.
On September 19, after deploying her launches for the day, officers and crew welcomed aboard the entire Cold Bay Elementary School – all eight students, teaching assistant Mrs. Lyons, and their teacher, Mrs. Burkhardt. The students are currently between fourth and seventh grade and go to school in a state-of-the-art, two-room school-house.
During the tour, the students learned about driving the ship and making nautical charts. They saw how sonars work, and they even used a sediment sampler to determine the seafloor composition.
The students were full of questions and enjoyed learning about life on a ship. They also captured the admiration of Rainier‘s commanding officer. “When Cold Bay residents describe their town, they can also boast of wonderful elementary school students who have a desire to explore new things,” explained Cmdr. Rick Brennan. “One of the great things about working on a NOAA ship is the opportunity to meet students like this. Combining our love of the sea with their enthusiasm for learning — that’s where America’s future hydrography starts.”
This student is ready to work!
The group examines bottom samples collected by the Rainier.
Cmdr. Rick Brennan explains how davits work.
- Cmdr. Brennan with friends — and potential future hydrographers.
In late May, NOAA Ship Rainier officially started her Chatham Strait hydrographic survey project in southeast Alaska. It’s often difficult to imagine the age of many of the depth measurements depicted on Alaskan charts, but this short animation brings it home.
The older picture is U.S. Coast and Geodetic Survey Steamer Patterson and her steam-powered launch Cosmos, surveying Gut Bay in 1897. (The USC&GS is one of NOAA’s predecessor agencies, and a direct predecessor of the Office of Coast Survey.) We juxtaposed Patterson with the Rainier, who is finally able to update the bathymetry — at the exact same location — 116 years later.
The Patterson was under the command of Lt. Cmdr. E.K. Moore, U.S. Navy, while Coast Survey assistants carried out the scientific work. In today’s Coast Survey, a NOAA officer — on the Rainier, it is Cmdr. Richard Brennan — is both commander of the vessel and its chief scientific officer.
The opening to Gut Bay is only about 100 yards wide – and it seems narrower!
“It must have been a real challenge to get the Patterson into this tiny bay in 1897,” Cmdr. Brennan observed. “The opening to the bay is only about 100 yards wide — and seems narrower than that when you are in the middle of it, since the cliffs rise almost vertically on either side.”
“We had the benefit of surveying the very narrow entrance’s seafloor with complete multibeam sonar coverage, and had the use of radar and GPS to inform us about our exact location as we made our way through the incredibly tiny opening into this bay. The Patterson (a steam powered sailing vessel) would have had to do this visually with only a few lead line soundings across the entrance. This must have made for an exciting navigational experience!”
Credit for photo of Rainier: Ensign Damian Manda
In June 2011, Coast Survey issued the first edition of the Arctic Nautical Charting Plan, a major effort to improve Arctic chart coverage that is inadequate for modern needs. After consultations with maritime interests and the public, as well as with other federal, state, and local agencies, we have issued the updated Arctic Nautical Charting Plan: A plan to support sustainable marine transportation in the Alaska and the Arctic.
“Maritime challenges are increasing in the Arctic. As multi-year sea ice continues to disappear at a rapid rate, vessel traffic in the Arctic is on the rise,” said Rear Admiral Gerd Glang, Coast Survey’s director. “This is leading to new maritime concerns, especially in areas increasingly transited by the offshore oil and gas industry and cruise liners.”
“Given the lack of emergency response infrastructure in remote Arctic waters, nautical charts are even more important to protect lives and fragile coastal areas,” Glang points out.
Commercial vessels depend on NOAA to provide charts and publications with the latest depth information, but many regions of Alaska’s coastal areas have never had full bottom bathymetric surveys — and some haven’t had more than superficial depth measurements since Captain Cook explored the northern regions in the late 1700s.
“Ships need updated charts with precise and accurate measurements,” explained Capt. Doug Baird, chief of Coast Survey’s Marine Chart Division. “We do not have decades to get it done; ice diminishment is here, now.”
We appreciate the perspectives offered by Alaska’s mariners in response to the 2011 Arctic Charting Plan. For instance, feedback called for adding a large-scale inset to the layout for the “Kotzebue Harbor and Approaches” chart, which we published as the first plan-inspired new chart, in April 2012.
The 2013 plan specifies 14 additional new charts, to complement existing chart coverage. Seven of the charts will fill gaps in medium-scale chart coverage from the Alaska Peninsula to Cape Lisburne at the edge of the North Slope, for coastal transits along the west coast of Alaska. Larger scale charts will provide for safer passage though the Etolin and Bering Straits, or for entry into harbors such as Barrow, the northernmost town in the United States.
The revised plan also adds NOAA chart numbers for all of the 14 future charts, and provides updated information and graphics describing the infrastructure and data needed to compile the charts.
The charting plan continues as a “living document,” as new concerns and challenges emerge. Anyone can submit comments through the Coast Survey Inquiry and Discrepancy System.