Pressure ridges















October 25, 1915;   Heavy pressure-ridges were forming in all directions....The pack within our range of vision was being subjected to enormous compression, such as might be caused by cyclonic winds, opposing ocean currents, or constriction in a channel of some description.  The pressure-ridges, massive and threatening, testified to the overwhelming nature of the forces that were at work.  Huge blocks of ice, weighing many tons, were lifted into the air and tossed aside as other masses rose beneath them. We were helpless intruders in a strange world, our lives dependent upon the play of grim elementary forces that made a mock of our puny efforts.  Ernest Shackleton, South
Ernest Shackleton standing in pressure ridges
January 3, 1911:  The land of Black (or White?) Island could be seen distinctly behind, topping the huge lines of pressure ridges.  Robert Falcon Scott  Journals: Captain Scott's Last Expedition

 [Pressure ridge with White Island in the background]


Robert Falcon Scott skiing near pressure ridges. 
 Black and White Islands in background

On the south side we could see the pressure ridges beyond Pram Point as of old--Horseshoe Bay calm and unpressed--the sea-ice pressed on Pram Point and along the Gap ice front, and a new ridge running around Cape Armitage about two miles off.  Apsley Cherry-Garrard (Scott Expedition).  The Worst Journey in the World

 [Pressure ridge off of Pram Point, the home of Scott Base.  These are probably about 20 feet high (flags in foreground are about six feet high.  Black Island in background.]   
Member of Scott Expedition climbing pressure ridge like the one above.













August, 1911:  In the course of the winter and spring, the pack-ice is forced up against the Barrier into pressure ridges of as much as 40 feet in height.  This took place only about a mile and a quarter from our hut, without our noticing its effect in the slightest degree.  In my opinion, if this Barrier had been afloat, the effect of the violent shock which took place at its edge would not merely have been noticeable but would have shaken our house.  Roald Amundsen.  The South Pole:  An Account of the Norwegian Antarctic Expedition

 [Same pressure ridge at two time points three weeks apart.  The ridge has gotten significantly taller.]

To the east, a great field of pressure ridges below, looking in the moonlight as if giants had been ploughing with ploughs which made furrows fifty or sixty feet deep:  these ran right up to the Barrier edge, and beyond was the frozen Ross Sea, lying flat, white and peaceful as though such things as blizzards were unknown.  Apsley Cherry-Garrard.  The Worst Journey in the World

 [Crevasse leading to pressure ridge over the Ross Sea]




 A wonderful mirage of the Fata Morgana type was visible on August 20....The principal characteristic is the vertical lengthening of of the object, a small pressure-ridge being given the appearance of a line of battlements or towering cliff.  The mirage is produced by refraction and is intensified by the columns of comparatively warm air rising from several cracks and leads that have opened eight to twenty miles away north and south.   Ernest Shackleton, South

 [Fata Morgana looking out across the ice.  All the black rectangles in the light blue oval that looks like buildings or cliffs are not really there. 

Now Pram Point [Scott Base] during the summer months is one of the most populous seal nurseries in McMurdo Sound.  In this neighbourhood the Barrier [the ice shelf], moving slowly towards the Peninsula, buckles the sea-ice pressure ridges.  As the trough of each ridge is forced downwards, so in summer pools of sea water are formed in which the seal make their holes and among these ridges they lie and bask in the sun: the males fight their battles, the females bring forth their young: the children play and chase their tails just like kittens. Apsley Cherry-Garrard.  The Worst Journey in the World

 [Seals at Scott Base with pressure ridges and Castle Rock behind.  Castle Rock was a life-saving landmark for the early 20th-century great Antarctic explorers heading home to the Ross Island huts.]




Video of mom trying to get her baby seal to swim in front of Scott Base at Pram Point.  He was having none of it.  This baby is about four times the size he was three weeks ago.  They gain 5 kg per day.



Comments

Lauren said…
The pressure ridges are amazing, but the seals? Gaining 5kg a day when they are young? Holy smokes!
November 22, 2019 at 11:25 PM
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