Dispatch 12: Reverse Deployment (ITP Recovery)     Print

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Fred Marin

September 23, 2019

Location: 78° 11’ N 151° 45’ W

Sea Conditions: 3817m water depth; Ice coverage decreasing throughout the day.

Exiting the ice cover of the high Arctic, we crossed paths with an Ice Tethered Profiler (ITP) that had been deployed by this same research expedition one year prior.  This ITP would have been left alone to continue collecting data for another year, except the profiler was no longer climbing its tether warranting a recovery if possible.  Jeff O’Brien from the Woods Hole Oceanographic Institution (WHOI), while on the ship with us, sent the ITP we are trying to locate an updated “mission” file.  This update told the instrument to get a GPS fix every 10 minutes instead of every 30, and to call back to the server every hour instead of twice a day.  So, sitting in the bridge in the early morning hours we are scanning the icy horizon for a yellow buoy when Jeff arrived with a GPS fix that was only 4 minutes old.  How far could this ITP drift in 4 minutes? The answer is not far.  Steaming a little further south to the GPS location, we sighted the yellow buoy hiding behind a tall piece of ice just off the starboard bow.  Technology is amazing sometimes.

To capture the buoy and begin the process of hauling the 800m mooring cable, I was fortunate enough to be sent over in the “man basket” with Cory Beatty (University of Montana).  It was kind of a surreal experience.  The water was crystal clear blue and churning form the ships “air bubbler system”.  The buoy was covered in giant ice crystals as it floated beside a large piece of ice that was stark white above the water line, and Arctic blue below.  We simply put a lifting strap through an eye on the buoy and connected it to the “bongo” winch.  We were hauled back onto the deck and the recovery process continued.

The profiler was in excellent condition, and we discovered that after this ITP had dragged across the submarine North Wind Ridge, a spring holding the idler pulley putting tension on the cable into the drive wheel had broken free.  This ITPs profiler and surface package will be fully recycled for a mission next year.  The yellow buoy however suffered the most damage from a Polar bear scraping at it with its paws! I think there were a few bite marks as well!

Why do we recover instrumentation that is intended to be expendable?  Autonomous instrumentation at the end of its life span is recovered whenever possible essentially to try and not litter the ocean.  In the case of the ITP, these instruments are deployed in late summer through fall, and have to survive harsh, dark, Arctic winters.  Many things happen to ITPs as they drift around the high Arctic seas.  Sometimes communication is lost and after many months, the instrument starts talking again sending home piles of backlogged data.  Some have their cabled mooring sheared by ice sheets overriding one another.  The most common case I have heard about is the 800m weighted tethers that hang feely in deep water encounters an underwater shelf and starts to drag its anchor.  This causes cables to break and the profiler itself to become damaged as it scrapes across the seafloor.  The hopeful scenario, is that after one or two years of data collection, the instruments batteries simply just run out.  At that point, the autonomous instrument has sent home a massive amount data collected like clockwork in one of the harshest environments on Earth.  All at the fraction of the cost, ship time, and number of personnel required to collect that volume of data in the Arctic by traditional methods alone!