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In the photos on this page we are measuring some properties of the sea
ice. Sea ice is just frozen ocean water, often covered by snow; it is
similar in that sense to the ice on frozen lakes, in that it is just
that the surface of the water froze. It differs from the ice I've
worked on before, in the interior of Antarctica, which fell as snow
and gradually got compressed into solid ice. Ice bergs are pieces of
ice that broke off of glaciers or ice sheets where they reach the
coast, so they are also formed from snow, not ocean water. Most of
the salt in the ocean water gets rejected as the water freezes, so the
sea ice is much fresher than the ocean water; sea ice that has
survived one or more summers is nearly salt free, and could safely be
drunk; sea ice that has been around for less than a year keeps up to
about a third of the salt from the ocean water, mostly in pockets of
very salty liquid water in the ice, leaving it still quite
salty. In these first photos we are preparing to drill through the ice to measure the thickness. To do this we use a normal battery-powered Bosch drill with the auger bits in the black case, in the first photo, and in Sebastian's hand, in the second. Each auger section is about one meter long, and they can be connected together to drill through six meters (18 feet) or more. After the hole was drilled, we could drop a weighted tape measure through to find the thickness. Most of the ice we worked on was about 1.5 meters (4-5 feet) thick, and it varied from 30 cm (1 foot) to more than 5 meters (15 feet) in ridges. The snow on top was usually around 20 to 30 cm (8-12 inches), and varied from 0 to more than one meter. |
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When we make the hole in the ice like above the only thing that comes
out of the hole are little, cut-up bits of ice, just like when you
drill through wood. In the photos below we are using a corer to take
out samples of the ice. Each core is about 3 feet long, and 3 inches
(8 cm) in diameter. After one core is removed, an extension can be
used to take the next piece deeper down. To drive the corer we use a
small 2-stroke engine or a T-bar and arms. |
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Here a section of core is being removed from the corer. |
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A section of the core ready for processing. |
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In these photos Anja and Gorm are measuring the temperature of the ice
core at different depths to see how much heat is getting from the
relatively warm liquid ocean water (around -2°C or 28°F) to the colder
air above the ice. Other cores are cut up to measure the amount of
salt in them at different depths. There are some algae that live in
the sea ice, so we also sometimes took cores to measure the amount of
chlorophyll in the ice. |
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| Work from the ship, Page 1 of 4 | |||
| Page 1 | Page 2 | Page 3 | Page 4 |
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Page created 19 July 2008, Last updated 19 July 2008 17:12 CEST.