Fate and Probability’s Tipping Hand — Mallory and Irvine on Everest in 1924 — an 18 Millibar Drop in Barometric Pressure

© 2010 Peter Free

 

23 December 2010

 

 

A slightly new hypothesis regarding what happened to George Mallory and Andrew Irvine on Mount Everest in 1924

 

ScienceDaily summarized research by G. W. Kent Moore et al. (published in Weather last August):

 

"We analysed the barometric pressure measurements and found out that during the Mallory and Irvine summit attempt, there was a drop in barometric pressure at base camp of approximately 18mbar. This is quite a large drop, in comparison the deadly 1996 'Into Thin Air' storm had a pressure drop at the summit of approximately 8 mbar," said Moore. "We concluded that Mallory and Irvine most likely encountered a very intense storm as they made their way towards the summit."

 

 

"Mount Everest is so high that there is barely enough oxygen near its summit to sustain life and a drop of pressure of 4 mbar at the summit is sufficient to drive individuals into a hypoxic state," said Dr. John Semple an experienced mountaineer and the Chief of Surgery at Women's College Hospital in Toronto.

 

 

The authors conclude that with the additional stresses they were under with extreme cold, high winds and the uncertainly of their route, the pressure drop and the ensuring hypoxia contributed to the Mallory and Irving's death.

 

 

© 2010 Everest Tragedy: Did Extreme Weather Cause Mallory and Irvine Disappearance? ScienceDaily (02 August 2010)

 

 

 

Citation

 

G. W. Kent Moore, John L. Semple, Dev Raj Sikka, Mallory and Irvine on Mount Everest: Did extreme weather play a role in their disappearance? Weather 65(8): 215-218 (August 2010)

 

 

What’s most interesting to me is the barometric pressure drop’s implication for hypoxia

 

Being killed by a storm on Everest wouldn’t be surprising, even today.

 

But imagine the added physiological pressure that suddenly lowered barometric pressure might have had on oxygen availability, even when climbing with the primitive oxygen gear that the Irvine and Mallory had.

 

 

What is a “bar”?

 

A bar is a unit of pressure equal to 100,000 pascal (Pa) or 100 kilopascals (kPa).

 

One bar is roughly the same as the pressure exerted by the atmosphere at sea level.

 

A pascal is a “Système International d’unités” (SI) unit of force per unit area equal to 1 Newton per square meter.

 

A hectopascal (hPa) equals equals 100 pascals.  Conveniently, 1 hPa equals 1 millibar.

 

A standard atmosphere equals 101,325 Pa or 1013.25 hPa.

 

A millibar (mbar) is one-thousandth of a bar, and therefore approximately one-thousandth of sea level atmosphere.

 

 

How much of an effect would a drop of 18 millibar be atop Everest?

 

Atmospheric pressure on top of Everest is 30 to 33.7 kPa, which is roughly one-third of that at sea level.

 

Eighteen millibars would be 0.018 x 100 kPa = 1.8 kPa.

 

The Moore research article said the 18 millibar drop was measured at base camp.  To simplify calculations, let’s assume that we can subtract the entire amount from the roughly 30 kPa that exists atop Everest in baseline barometric conditions:

 

30 kPa – 1.8 kPa = 28.2 kPa

 

Percentage-wise:

 

28.2 kPa is 94 percent of 30 kPa

 

 

Could make a noticeable difference

 

Since ordinary folks have trouble breathing without oxygen supplementation, even in good conditions on Everest, one can see how reduction of 6 percent in available oxygen would have implications.

 

Especially so for two men struggling to cope with bad weather and probably deepened heat loss due to wind-chill and possibly reduced absolute temperature.

 

Pertinent to this analysis is a 2007 study of four climbers descending from the Everest summit.  Measurements showed that their blood oxygen saturation levels varied (from one person to another) between 34.4 and 69.7 percent at an altitude of 8400 meters (27,559 feet).

 

Michael P. W. Grocott et al., Arterial Blood Gases and Oxygen Content in Climbers on Mount Everest, New England Journal of Medicine [NEJM] 360(2): 140-149 (at Table 2)  (08 January 2009)

 

Everest’s peak is still higher at 8848 meters (29,029 feet — although the National Geographic Society thinks it may be 6 feet taller).

 

Given already very low blood oxygen saturation levels at 8400 meters, one can see that even the apparently trivial difference of 18 millibar in atmospheric oxygen pressure might have mattered a great deal, especially if the climbers approached the still more oxygen-scarce conditions at 8848 meters.

 

 

Fate’s weather or probability’s axe?

 

Could this 18 millibar drop in pressure have been Fate’s sad final tipping hand for George Mallory and Andrew “Sandy” Irvine?

 

Or, less romantically, did the knife-edge probabilities that existed on Everest on 08 June 1924 simply outrun the climbers’ odds of survival?

 

 

Fate and probabilities

 

Americans (especially) don’t like to admit it, but our illusions of control regarding our personal destinies are false.

 

 

Read briefly more about Mallory and Irvine on Nova’s website

 

Liesl Clark & Audrey Salkeld, The Mystery of Mallory & Irvine ’24, Nova Online Adventure (November 2000)