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Dispatch 8: Going Exploring

9th August 2012

Siglufjordur, Iceland Harbor Approach

The ship seems a bit bereft this morning of both gear and people.  The mooring work complete—with great success, thanks to fair weather and skillful technicians and ship handlers—we dropped off six of our number and several tons of their gear in the little fishing town of Siglufjördur at the apex of a glacier-carved notch in the northern coast of Iceland.  In only eight days, this team recovered fourteen moorings, extracted their stored data, and redeployed ten of them north of Iceland and in the Denmark Strait.  Though the odds were stacked against it, every one came back intact bearing complete data sets.  “That,” said Bob, “is off the charts.”  So now, after the year-long knowledge gained from twelve moorings that had been strung picket-fence fashion across the Denmark Strait, Bob and his international colleagues have left but five moorings in the most propitious spots to measure the through flow.

In the wee hours of yesterday morning, light wind, glassy flat seas, mountains materialized out of the fog.  Only isolated patches of snow spatter the higher elevations, but the signs of ancient ice, cirques and arêtes that look cairns built by trolls, and other alpine features, are apparent everywhere.  If Ice Age glaciers formed a first draft of this coast, contemporary erosion continues to rewrite it.  Silver ribbons of waterfalls slice deep gorges in the mountain flanks.  Parallel rows of steel revetments mounted on the steeper slopes wait to protect the little town from winter avalanches that further erode the landscape, geologic time in fast-forward mode.

By 0800, the bridge watch had their ship smack on the range marks leading to the harbor.  An hour later, Captain Chapman, with his usual aplomb, eased her against the industrial wharf where customs people waited to clear us off the ship for a stroll around town.  We said a fond goodbye to our departing friends, Roald and Lorendz from NIOZ, Jim and Murph from WHOI, Hedinn and Steingrimur, the Icelandic oceanographers.  By 1600, we were underway again, and Iceland, like Greenland before it, faded astern in the fog.  That completed what let’s call part one of the cruise.  Part two, the study of the East Greenland Current, now begins.

Old Lighthouse
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Both parts, however, are directly concerned with the flow through the Denmark Strait.  In a previous post (please see “OVERTURNING), I described broadly the northward surface flow of warm, salty water from the Gulf Stream System into the Nordic Seas and the return flow of cold, dense water at depth called the Meridional Overturning Circulation (MOC).  Now before we get much farther north, let’s take a closer look at the flow through the strait itself.

As If We Were Tourists

The old paradigm held that the dense water in the East Greenland Current, some of it flowing south out of the High Arctic, accounted for all the water passing through the strait.  But in 1999, our Icelandic friends, Steingrimur Jonsson and Hedinn Valdmarsson, “blew that idea out of the water,” as Bob put it.  Monitoring with ADCPs the slope waters close aboard the north coast of their island, they noticed a margin of enhanced flow in 600 meters of water.  It looked a lot like a current.  But nobody had ever heard of such a thing.  Could this actually be a new current?  Well, maybe.  But it might just as well have been some tidal phenomenon or a short-term variation in something or other.  So they went back for another look.  And there it was again, flowing from east to west toward the Denmark Strait.  It wasn’t enormous, about one million cubic meters of cold water per second, but that’s not trivial.  In 2004 Hedinn and Steingrimur published a paper in the technical journal Geophysical Research Letters, proposing that it was indeed a new current, and what’s more, it contributed a “major” portion of the water entering the Denmark Strait.

This notion was very intriguing, but it was based mainly on velocity measurements with little hydrographic information, that is to say, minimal temperature and salinity data to identify its fingerprint.  The Icelanders recognized that of course, but they lacked the ship time to perform extensive measurements.  Physical oceanography is expensive, and since there’s no pending profit in it, private enterprise doesn’t participate.  Funding must come from governmental organizations such as the National Science Foundation in the U.S. and its counterparts abroad.  Still, this question of a new current, and not just any new current, but one contributing significantly to the Denmark Strait Overflow, had to be answered; it was a potential paradigm shifter.  That’s where Bob and his colleague Kjetil entered the picture, spelling the beginning of what yesterday Bob called a “career changing collaboration with Steingrimur and Hedinn.”
In October 2008 on a cruise aboard R/V Knorr to retrieve and redeploy several moorings in the Denmark Strait, Bob and Kjetil managed, between storms, to run CTD sections athwart the mysterious current.  Sure enough, it was there right where the Icelanders claimed, hugging the Iceland shelf and flowing from east to west—into the strait.  (Incidentally, that cruise began for me a career changing collaboration with Bob and treasured friendships with him and several others presently aboard JCR.)

Inside Siglufjordur Harbor

'To discover it’s true nature, its ways and means, is the objective of this, the second half of the cruise.'

Bob, Kjetil, Steingrimur, and Hedinn returned to the region aboard the Icelandic R/V Bjarni Samundsson in 2009 to run more hydrographic and velocity lines across the current.  Then everyone went home to analyze the data.  Yes, the current actually does flow around the northwest corner of Iceland into the strait, no question about it.  So now it needed a name.  In exploration, the privilege of naming the new traditionally falls to the discoverer(s).  The Icelanders settled on the North Icelandic Jet (NIJ).  But the current’s existence, now affirmed, presented multiple questions:  Where did it come from?  What caused it?  More data was necessary before old paradigms fell to the new.  That came last year, again aboard R/V Knorr.  Bob and Kjetil proved that the NIJ does not flow from elsewhere, but originates right there on the Iceland shelf, result of a complex oceanographic process that we need not expound, since the details of the NIJ are not our present concern.  The important point for us now is that the NIJ supplies some fifty percent of the cold dense water flowing through the strait, thence southward to sustain the integrity of the vital Meridional Overturning Circulation.

That brings us to today and to that other approximately fifty-percent component of the Denmark Strait Overflow—the East Greenland Current (EGC).  Like so much else involving the ocean, the EGC is not the straightforward stream of water the community once assumed.  To discover it’s true nature, its ways and means, is the objective of this, the second half of the cruise.  We’re going exploring.
- Dallas

Mountains Above Siglufjordur