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FISH SAFE: Reducing risk – Icing by the numbers

Jan. 27, it will be eight years since the 76′ trawler Lady of Grace sank off Nantucket with her crew of four.  It is a tragedy that is still easily recalled and deeply felt by those in the port of New Bedford.

Following a yearlong investigation, the Coast Guard concluded that the primary cause of the casualty “was most likely attributed to a dramatic decrease in stability due to the added weight from a significant accumulation of ice.”

Since then, we have learned a little more about predicting, preventing, and mitigating ice buildup.

backus-SHA group made up primarily of oil drillers and transporters who work in the Arctic environment is actively addressing the phenomenon of icing and, through a joint industry project, has produced the “Arctic Operations Handbook.”

The chapter titled “Impact of Marine Icing on Arctic Offshore Operations,” written by Robert Platt and published in December 2013, contains interesting data and observations regarding icing.

For example, the report characterizes icing as “slow,” “fast,” and “very fast” and provides objective numbers for each category.  You can download the chapter for free at <www.arctic-operations-handbook.info>.

It’s worth a read.  But, basically, the risk of icing begins to increase when the air temperature is below the freezing point of seawater, which varies with salinity but is around 28.4°F, and when the water temperature is 46.5°F or less and the wind speed is 19.4 knots or more.

 

Icing risk area

Coast Guard regulations specify certain actions related to stability that must be taken to reduce the risk of icing when a fishing vessel is operating north of 42°N, which is about the latitude of Boston.

However, a 2008 report by two students at Worcester Polytechnic Institute titled “The Effects of Icing on Commercial Fishing Vessels” found that icing conditions routinely occur south of 42°N and made the recommendation that the standards be changed to include areas north of 38°N, which is just south of Ocean City, MD.

The students analyzed weather buoy data from 1997 through 2007 and found that Boston, at 42.3°N, had 287 icing events from Dec. 1 to April 15, while Delaware Bay at 38.464°N had 91 icing events from December (one event in December) through the end of March.

Here’s the take-home message:  Be vigilant while fishing during the winter months about checking weather conditions – even if you fish as far south as Delaware Bay – to reduce your risk of an icing event.

 

Weather information

Fishermen have their favorite, efficient methods for checking air and sea temperatures, wind speed, and icing conditions.

But a good website is available if you Google “Ocean Prediction Center,” a program of the National Oceanic and Atmospheric Administration.  Click on “Probabilistic Guidance” for wind speed, marine forecasts, and other information.

The Naval Postgraduate School’s Meteorology Department provides a program to calculate the risk of icing at <www.met.nps.edu/”psguest/polarmet/vessel/predict.html>, as well as a host of other information.

From this website you can move to a helpful discussion called “Mitigation and Avoidance of Vessel Sea Spray Icing.”  This page lists tools – a baseball bat, for example – for removing ice from surfaces.  It also includes vessel maneuvers for reducing ice accretion, as well as a caution that turning a vessel with heavy ice buildup is a very high-risk maneuver.

 

Ann Backus, MS, is the director of outreach for the Harvard School of Public Health’s Department of Environmental Health in Boston, MA.  She may be reached by phone at (617) 432-3327 or by e-mail at <abackus@hsph.harvard.edu>.
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Read the rest of this story and much, much more in the January issue of Commercial Fisheries News.  Buy this issue or Subscribe.   

(Read online immediately with access key and download for future reference.)

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