Mainly kayaking photographs taken on the Isle of Man and beyond.

Sunday, 31 January 2010

Sea Kayaking Isle of Man - Sea Temperature.

On Saturday as Ian, Jess and myself paddled down to the monstrously savage tidal races at the Calf, the sea temperature was about 7 degrees C. The air temperature was less at about 4.5 degrees C. Water conducts heat about 25 times more rapidly than air and immersion in cold sea water can be rapidly fatal. Survival at 7 degrees C sea temperature is about 1 hour. Of course, wearing the correct immersion clothing can markedly prolong this. Neoprene full immersion suites can prolong the survival time for up to, but not a guaranteed, 24 hours. We all use Kokatat full dry suites with fleece liners underneath. The dry suite itself will provide virtually no insulation and the fleece undergarment is essential. Unfortunately, this is not the end of the story as up to 75% of body heat can be lost through the head alone. Factor in some failed roles and some failed re-entry and roles and without head protection survival time is markedly shortened. There was always a good chance of rolling yesterday and we were wearing neoprene or aquatherm head hoods. This gear is not the same as a full neoprene survival suite, and survival time in these temperatures would be much less than 24 hours.
Of course survival time is not the same as the time the immersed paddler remains fully functional, which can be much shorter. The definition of hypothermia is a core body temperature of 35 degrees C or less. Mild hypothermia is defined as a core temperature of 32 to 35 degrees C, and moderate hypothermia as 28 to 32 degrees C, the latter having a mortality rate of 21%. Hypothermia depresses the function of every organ in the body. Cardiac output is halved at a core body temperature of 28 degrees C, heart conduction defects occur below 33 deg C, and ventricular fibrillation (VF) occurs below 28 degree C. VF means no blood is pumped by your heart to supply your brain and body and you will probably die. All this is preceded by confusion and muscle rigidity preventing further self rescue attempts and ultimately preventing swimming. Breathing is depressed and airway protection declines possibly allowing suffocation by sea water.
So, if you enjoy extreme sea kayaking in the Winter like we do then make sure you have the right gear and don't paddle alone.

1 comment:

Rob said...

Don't be deceived. With sea temperatures about 7 degrees (C), it may take an hour to become hypothermic. Problem is, the limbs will stop working in about 10 minutes. I love your the kayaking photos on your blog and wouldn't be out in those type of seas without a dry suit.

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