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> 09-11-05: Lomonosov Ridge
Ute_Kaden
post Sep 12 2005, 11:12 PM
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Lomonosov Ridge
9-11-05


Ship Position at 2005/09/11 22:45:01 UTC -
Longitude: 176 53.313 W Latitude: 89 24.256 N
"IBCAO" depth: 3625 m Multibeam depths: 3707.0 m

In the pipe (announcement through ships loud speakers) 5 min ago it was announced that the helicopters from Healy and Oden have landed at the North Pole! North Pole we are coming!

We are transiting to the North Pole. Estimated arrival time for the ships is in several hours, Monday, 9/12/05.

During night we traveled through very heavy ice. I could feel it by the bouncing and vibrating of my whole bunk bed which woke me up four times. The Captain got called to the bridge to avoid getting stuck in the ice. Captain Dan Oliver has extraordinary experience and skills for the Arctic. In the morning at the bridge he showed us the path of the ship with the familiar zig- zag pattern and said thoughtfully:” We beat the hell out of the ship…” No, we did not get stuck and I developed a deep respect for the engineers that constructed the ship; strong hulls and engines. The transverse trip to the North Pole gives me time to report on something special.

"Is there a Gap in the Lomonosov Ridge?"

"Mare incognitum, The Arctic Ocean, is despite its critical role in
global climate evolution, the only ocean basin whose history is virtually
unknown. Investigating the Arctic Ocean is certain to yield scientific
and technological benefits to the Society." (COMPLEX, 1999)

What fascinates me on our trip through the Arctic Ocean it the exploration of the unknown. Our scientists answer some of my questions with, “We really don’t know”. Realizing that the seismic images that come back from the ocean floor are the first images ever seen by man of an unknown area makes us feel a bit special on the Healy. What we know so far about the ocean floor is compiled on the Bathymetric map of the Arctic Ocean (IBCAO), the international chart of the bathymetry of the Arctic Ocean (depth chart) and Dr. Martin Jacobsson onboard of the Healy is one of the leading scientists working on the development and update of the map. Martin Jacobosson made me the small maps so you can locate our survey stations. Thank you Martin!

IPB Image
Map about our survey area

Yes, not all the areas on the map got surveyed yet. Sometimes the data we have is sketchy and very little swath (multibeam data ) is available from this remote location of the earth. The lack of adequate site survey hampers the general understanding of the area. This adds to the importance of the seismic data collection of our cruise.
Our ship surveyed the Lomonosov ridge two days ago. The Lomonosov Ridge is more than 1500 km long and less than 150 km wide. Data suggests that is a continental fragment.

The buzz on the ship was about “The Gap” in the Lomonosov Ridge. Does it exist? On the current IBCAO map the Gap was several thousands of meters deep. The Gap functions as a place of water exchange between the eastern and western hemisphere.

When the data came back it turned out that the gap is not as deep as we thought. “A kind of gap, a shallow gap, a small gap….”,are the comments of the astounded scientists. Well, let the swath bathometry speak …

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IPB Image
IPB Image

Map of our multibeam swath over the "Gap" in the Lomonosov Ridge

It is absolutely cool to see that we do not know everything about our earth and some things we think we know may be incorrect! Science in action.

Best regards,
Ute

What is echo sounding?
Sonar-swath bathymetric survey , SEA BEAM Multibeam ocean floor mapping


Echo sounding is a technique for measuring water depth by transmitting acoustic pulses from the ocean surface and listening for their reflection (echo) from the sea floor, recording the time. This technique has been used since the early twentieth century to provide depth input to charts that now map most of the world’s water-covered areas so ships can navigate safely. In addition, information derived from echo sounding has aided in laying trans- oceanic telephone cables, exploring and drilling for oil, locating underwater mineral deposits, and improving our understanding of the earth’s geological processes.

In 1964, SeaBeam Instruments (at the time the Harris Anti-Submarine Warfare Division) developed the multibeam depth sounding which gives higher resolution of wide swaths of the ocean floor with each ping. Historically, the system was developed and used to detect submarines or mines.

The Healy uses a Seabeam 2112 Bottom Mapping multibeam sonar system for bathymetric surveying . Sonar is for detecting objects in water using sound.
Sound pulse (Ping generation), propagation, echoing and reception

The SEA BEAM system sends a sonar signal (ping) at 12 kHZ from projectors (sound source) mounted along the keel of the Healy forming a single beam projected across a swath (area on the ocean floor perpendicular to the path of the survey vessel) under the ship. The sonar signal travels to the sea floor and is reflected back. Hydrophones mounted across the bottom of the ship listen to the reflection signal. Computers process the signals based on time and signal intensity. The system integrates sonar data with GPS location of the ship and produces real time images (depth) of the ocean floor.
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