August 26, 2012
to be posted on nobabies.net
H. Elderfield
Godwin Laboratory for Palaeoclimate Research
Department of Earth Sciences
University of Cambridge
Downing Street
Cambridge CB2 3BQ
UK
he101@cam.ac.uk
Dear Dr. Elderfield:
My ignorance of things palaeoclimatic is exhaustive. My English professor older brother says he does not use the social network “twitter” because he says a “twit” is someone who can safely by ignored. That would be I, in this context. But I make bold to write because I maintain a web site that invites some serious thinking about first biological principles, and I understand that among hyenas anyway, the generally curious are also the best specific problem solvers. I need those folks, and they need a wide range of inputs so I frequently get off topic, like now.
Your article (H. Elderfield [What a marvelous name.] et al. Evolution of Ocean Temperature and Ice Volume through the Mid-Pleistocene Climate Transition SCIENCE vol. 337. no. 6095 August 10, 2012 page 704) has disabused me of a couple of things. I had believed that the North Atlantic Conveyor (fed by the good old Gulf Stream) was the source of the coldest deepest water. Now you point out that it is the Great Southern Ocean. I feel better about that. The North Atlantic seems to me to be a rather obscure corner of creation (to use a popular if misleading term) and the Great Southern Ocean seems intuitively the better bet. Not that I know where it is. I suppose it is definitely not the North Atlantic. I know where the North Pacific and South Pacific used to be, but I thought there was a continent at the South Pole, not an ocean. Not that I understand the continent. When they say “western Antarctic” I think, “West of what? You don’t talk about the “eastern equator. Why not say, The Pacific Antarctic?”
The next correction I received was the concept of the Mid-Pleistocene Climate Transition. I had thought everybody agreed that ice ages were forced by changes in the earth’s orbit caused by our position, or rather the position of our aphelion, relative to Jupiter. I can’t say I much like the idea. Jupiter is pretty far away. But then some time about 1240 to 700 thousand years ago we changed from a cycle of ice ages that lasted about 41 thousand years for a cycle and was rather mild to a regime with ice age cycles of greater intensity and about 100 thousand years duration. Jupiter didn’t change much.
Am I following you? Are you still there?
The transition apparently was due to an enormous build up of ice in Antarctica. I suppose we are nearish the end of a warm spell and approaching the beginning of a new, very bracing, ice age.
I have a different idea about the Mid-Pleistocene Transition. (Just keep saying, “This isn’t serious. He admits he’s a twit.”)
In the summer the Arctic Ocean undergoes partial melting, refreezing in the autumn. This creates a sort of Maxwell’s Demon, letting energy in but not out. I should imagine this contributes to global warming.
One imagines the arctic ice cap totally gone, the North Pole being the hottest place on earth and the heat forcing its way to the cold of the South Pole. Locally this would be manifest as an enormous cyclonic storm, sort of a really big thunder storm shedding hailstones of such size and number as to survive for years and ultimately to build glaciers. The abrupt return of ice ages is suggested by animals frozen in ice with plants that had been flowering hours to days before ice covered everything and by the Grasshopper Glacier, now pretty much gone but not that long having grasshoppers for quite some vertical distance meaning ice accumulating at that depth in a day or so. (I haven’t seen it or a professional description, only travelers’ reports.)
So far as I know, that ice cap has survived numerous recent ice ages, so it can’t be the cause of the more recent 100 thousand year cycles. But ah, maybe the earlier cycles.
I have no idea, but you may be able to dismiss this out of hand. Land moves around. The Arctic Ocean is now almost land locked. That would seem to be the ideal setup for a regime of cycles forced by the melting of the ice cap, followed, after sufficient glaciation elsewhere had lowered sea levels to the point where the Arctic Ocean was more completely land locked and shallower, followed by freezing and a new cycle.
So back at the beginning of the Pleisotcene, how did plate tectonics configure the Arctic Ocean?
In your excellent article, where you analyze the past climates with multiple elegant isotopic studies, it appears that there was an accumulation of ice in the Antarctic at the time of the transition. Maybe it was caused by the north-to-south flow of moist air, still relatively wet despite having dropped all that hail.
Sorry, there is a gaping hole in this. Why the change in the air flow just then? A change in the configuration of the Arctic Ocean caused by the pavane of tectonic plates? I have no idea.
All best wishes.
Sincerely,
M. Linton Herbert MD
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