Ice Navigation RV Mirai Deployment 2013 #4

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It is the Arctic.  Everything changes constantly.  Weather changes, the ice changes.  Plans change.  Most often it is the variability in ice conditions that cause plans to change.  This time, it was weather.

Having passed the Arctic Circle and into the Chukchi Sea on the morning of the 31st, RV Mirai had begun a transect line along longitude 168º45’W, stopping to occupy science stations every 30’ of latitude.  The plan was to proceed steadily northward towards 72ºN, then alter and run towards Point Barrow to conduct a number of current mooring recoveries and redeployments.  All was going very well on the 1st of September as the weather about the ship remained sunny, winds NE light to moderate, just about right.  At the most complex stations, a full suite of sampling was conducted including the 36 bottle CTD rosette, NORPAC plankton net hauls, PRR and HydroScat casts, at others, only a CTD/rosette cast.  In addition, every three hours, the increased frequency of radiosonde launches that were being matched by Russian, American, Canadian, Danish and Norwegian meteorological stations ashore to collect data on Arctic cyclones.

But then things change in the Arctic.  Some things have been changing for the better…the ice has been continually retreating and melting.  Not quickly but enough to be noticeable in the daily ice charts.  But the weather has been changing as well.  With brisk easterly winds confidently forecast to be blowing over the region that the original plan would have us attempting to recover current sensor moorings on the day scheduled, a quick change in plan was called for.  Instead of continuing north to 72ºN to finish the transect mid day on the 2nd of September, after completing the 10th station on the line, 53’ west of Cape Lisburne on the 1st, the Mirai altered course to sail directly for Point Barrow to work the mooring a day ahead of the expected high winds.

A wise choice given the sensitive current sensors and moorings that must be delicately recovered after moorings are released from the bottom by radio control and the sensor strings float to the surface and then are gingerly brought onboard.  However things don’t always go according to plan.  Of the two moorings that were targets on the 2nd, only one was successfully recovered, a subsurface hydrophone placed to record whale sound and activity over the last twelve months.  The second, a current recording mooring responded to transponder pings but would not release.  By late afternoon winds had freshenedand were above the limits for recovery and snow squalls were blowing through, so Mirai turned back to occupying observation stations, planning to return later to again attempt recovery of the mooring when conditions moderated.

We continue to watch the ice conditions around us.  NOAA, TOPAZ and AMSR charts all indicate continued degradation of ice and the further retreat northward of the ice edge. We adjust plans accordingly day to day based on the ice data and weather information received.  Conditions remain positive for continued melt and retreat of the ice through the month of September.

Capt David (Duke) Snider
Ice Navigator
RV Mirai

 

 

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