SO .. now we have it in the Chukchi headed north
and we need to explain how it gets into the Arctic. That is one of
the main questions of this whole project. I can give you some ideas.
One is again the winds - they push it off the shelf over the deep
basin. One is just gravity. As it flows over the shelf, it's denser
than the water it flows into and so it flows down. Because the earth
is spinning, ocean currents like to turn to the right in the Northern
Hemisphere, so quite a lot of the waters flowing out of the Chukchi
Sea (past the moorings we picked first in the trip) turn right and
flow along the north coast of Alaska (past the moorings we just finished
with yesterday). There again the wind can push it off shore and/or
the current can "go unstable" and little bits of it break
off and form eddies (large [about 5 miles across] rotating blobs of
water, big, slow whirlpools if you like) and these can move off into
the Arctic. We see the waters from the Chukchi Sea right out in the
central Arctic, and even exiting the Arctic in Fram Strait east of
Greenland, in a layer about 300-450 feet down in the ocean. I don't
think much of the shelf water actually gets down much deeper than
this. Some people talk about plumes of really dense water formed on
the shelves plunging down the side of the Arctic Ocean to great depths
(1/2 a mile or more), but no-one has found them yet."
Dispatch 27 - October 6, 2003
By C. A. Linder
Weather conditions: Overcast skies, 45 kt winds gusting to
55 kts, 10-15 ft seas, air temperature 28°F
Nick of Time
We deployed the moorings yesterday in the nick of time! As night
fell another arctic gale hit us, bringing our CTD operations to
a halt at 2:30AM. The storm increased in intensity through the day,
peaking at a sustained wind speed of 50 knots! Standing on deck
felt like sticking your head out of a car window driving down the
highway -- in winter... Even bundled up, after several minutes on
deck my head was throbbing like I had an ice cream headache. Nothing
I had to wear could stop that icy wind from cutting through.
Since science operations were canceled, it was a welcome day of
rest for most of the science party. Thanks to the marvels of satellite
technology, half of the science party was glued to a laptop in the
science lounge watching a webcast of the Boston Red Sox vs. Oakland
A's game. A crowd also gathered on the bridge to watch Healy
meeting the fury of the gale. Every
few minutes the ship would hit a particularly large wave at just
the right moment, sending spray flying
as high as 70 feet in the air. It was an incredible sight, and several
crewmembers videotaped the experience from the safety of the bridge.
We also gained a new appreciation for how stable the Healy
is in rough seas. A smaller vessel would have been lost in the 15
foot wave troughs today, but the Healy cruised along with
only minor rolls and pitches.
Another elementary school class has joined our online expedition!
These questions come from Mrs. Lyons' 5th grade class at
Mt. Alvernia Academy, Chestnut Hill, Massachusetts.
Question from Sam: Why does the water flow from the Chukchi Sea into the Deep Basin?
Answer: I asked Chief Scientist Rebecca Woodgate
to answer this question. She has been studying the physical oceanography
of the Arctic for over a decade.
"We have some ideas of why water flows north through the Chukchi
into the Arctic, and it's to do with the ocean and atmosphere circulation
of the whole world. Basically, water evaporates from the Atlantic
ocean, is carried over to the Pacific ocean by air currents, and
rains back down on the Pacific. So now we have "too much"
water in the Pacific and it has to get back somehow, so it flows
back through the Chukchi Sea and the Arctic. That's part of it.
The ocean currents could be doing the same sort of thing - pushing
too much water into the Pacific, so it leaks out at the top into
the Arctic. We call these effects "pressure head" effects,
because there is more water on one side (the Pacific) than on the
other (the Arctic) and so that drives a flow. It's the same effect
as causes your toilet to flush - kinda. The winds drive the water
in the Chukchi Sea too, but the average wind is actually
towards the south, and tries to drive the water back south against
this pressure head. The effect of the wind is however less than
the pressure head effect, so on average the water still goes north.
Question from Victoria: Is this the coldest place you have ever been?
Answer: Hi, Victoria. Believe it or not, the weather
actually hasn't been that cold so far on this trip. I can recall some
mornings waiting for the bus to take me to high school in Wisconsin
that were much colder than out here... And this past winter you surely
remember that week (or was it two?) when the temperature in Massachusetts
hardly broke out of the teens. I will say this, though - this is the
coldest I have ever been in October!
Our latest weather forecast calls for the storm to begin subsiding by tomorrow afternoon. As soon as the weather permits, we will be resuming our high resolution CTD section alongside the mooring array.