A Very Deceiving Night: High Pressure

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A thermal inversion would normally cause water vapour near the surface of the sea to be prevented from rising up into the warmer, less dense air above, forming a thick fog within the inverting layer.  However, examination of the weather records for Titanic’s wreck site on the night of the sinking reveals that she sank in the centre of a 1035mb Arctic High.  This was the highest pressure in the northern hemisphere at that time and is a most unusually high pressure to be experienced on the North Atlantic in April:

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Northern hemisphere synoptic weather chart, 15th April 1912

As well as compounding the high density of the cold air near the sea surface that night, the sinking air in a high pressure system is always clearer than the air it replaces because it does not contain aerosols, which originate from processes at the Earth’s surface, such as fires, dust, sea salt, pollen, industrial pollution, etc.

In fact, the air in this system was particularly clear, as the high had formed almost directly over the North Pole, on 8th April 1912, and had swung down to Titanic’s wreck site along the non-industrial and almost unpopulated northern plains of Canada.

Moreover, because the sinking air heats adiabatically as its pressure increases, it reduces its relative humidity and this causes any moist aerosol particles to lose water and thus shrink.  In effect, the aerosol is dried out in the air descending in a high-pressure system and smaller, dried aerosol particles are less effective in scattering light than larger water droplets. This caused the visibility at Titanic’s wreck site to be increased to well beyond the normal levels of seeing.

By overlaying this synoptic chart onto the satellite image of water temperatures at Titanic’s wreck site, one can see that Titanic sank in the centre of a ‘perfect storm’ of atmospheric conditions, conducive to both increased visibility and abnormal refraction:

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Combination of synoptic chart and thermal image of Titanic’s wreck site, reveals the “perfect storm” in which Titanic sank

I hope by blogging chapters from my book, A Very Deceiving Night, it will contribute to the ongoing discussions regarding the atmospheric conditions on the night of the tragedy and the true causes of the disaster. At the moment, the book is only available as an e-book. If you wish to purchase it then you can do so in Amazon Kindle format here and other formats, including Apple, Kobo and Nook, here. Thank you.

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