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> 08-30-05: Dirty ice, holothurian..., ...and a sextant navigation lesson
Ute_Kaden
post Sep 2 2005, 08:57 PM
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Dirty ice, a holothurian and a sextant navigation lesson
8-30-05



Ship Position Information at 2005/09/01 00:57:01 UTC
Longitude: 150 59.913 W Latitude: 84 10.504 N
"IBCAO" depth: 2562 m Seabeam Centerbeam depth: 2504.8
Speed: -0.3 Heading: 305.5 Water Temp: -1.579 Sal: 29.92 Fluor: 0.092

Last night, thick multiyear ice slowed us down to about 1 knot average speed with a lot of backing and ramming (back and forth) to go through the ice up to 5 m thick. At pressure ridges ice can be as thick as 12 m and more. We try to avoid pressure ridges at all costs.

Since two days we see continuous dirty ice floes (ice with mud and grains in it, sometimes grass and other organic materials). The scientists are very excited about this. We had not seen any below 82 N. Glenn, Martin and Dennis went out on the ice to collect bags of dirty ice. This will help them to understand the ocean ice drift. The Fe- grains will function as the fingerprint to trace the source of the dirty ice. If it turns out that the dirty ice originated in the Siberian coastal waters near the Lena River in the Laptev Sea, it would confirm the models of ice drift in the Arctic Ocean.

Ruben, Sandrine and I helped Glenn recovering the multi core from a depth of 1800 m. Remember; the multi core gives us the top 40-50 cm of sediments of the ocean floor. Guess what, we found an unusual little critter in one of the cores-excitement! Look at the photos. How cute it is. Leonid and Dale are recognized as biology knowledgeable people and got called in to identify the thing. “A sea cucumber (holothurian)...”, was the judgement. Well, whatever that is… (Physics teacher comment).

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The highlight of the day was a lesson in nautical navigation by Garry Brass. Garry ,a sailor himself, loves nautical navigation and has a collection of sextants. He has brought on of his “Babies “onboard of the Healy-you know, just in case our 3 GPS systems malfunction, so we can find our way home. After waiting several days for a suitable celestial object to appear in the sky the sun came out and we were in business.

I got a lesson in how to use the sextant and take a sun reading. Very interesting is the path the light takes through the mirrors and lens system. As legend says, in the old days navigators got blind in one eye because they had to look at the sun to fix the ships position during the long cruises. Not to worry, never look in the sun, we had sun filters on the sextant.

Writing down the readings and we went back to nautical books and tables, tables, tables. After lots of number crunching, adjustments for altitude, dip correction, corrections for parallax, declination, refraction, polar temperatures, air pressure…and some admiration for the Royal Society in England we found out that the ship’s GPS was off by 20 nautical miles smile.gif . Pretty good! This exercise renewed my deep respect for the old sailors that set out to circumnavigate the globe and actually found the right way. On the contrary a lot of them got lost…Glory to the GPS system.

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Sextant - A double-reflecting instrument for measuring angles, primarily altitudes of celestial bodies. As originally used, the term applied only to instruments having an arc of 60 degrees, a sixth of a circle, from which the instrument derived its name.

Best regards,
Ute
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