Saturday, June 14, 2014

West Antarctic Ice Sheet: Who Cares?

So the oceans rise by nine feet ... we all will be long dead.

One hears occasionally about the West Antarctic ice sheet "collapse". That seems pretty far off and over-wrought. How can ice sheets collapse? That doesn't make much sense. If an ice sheet is already over the ocean, then its melting wouldn't affect the water level anyhow. So what is the deal?

In this case, the sheet is a large land-based glacier (not an ice shelf, like the Ross ice shelf) whose bottom lies far below sea level by nearly 4,000 feet, though its top rises up over sea level by another mile. This glacier holds about a half million cubic miles of water. Its collapse is going to take maybe 400 years: fast if you are a geologist, but pretty slow for most other people, so it is a bit of a misnomer. Perhaps megamelt might be a better term.

Thwaites glacier forms most of the West Antarctic ice sheet that is shrinking and being undermined.

The problem is that most of the glacier is over land that is far below sea level. Over the last (cold) millennia, it has pushed all the sea water out and stabilized as an enormous glacier. But with climate heating, sea water has begun infiltrating under the glacier, and, with its salt, is going to undermine the whole glacier, melting it far more rapidly than the rest of Antarctica is going to melt in response to rising air temperatures. That is what the observers are talking about.

Cross section view showing how much of the glacier is under sea level and prone to  "collapse".

The researchers in a recent paper describing this situation do two things. They state that based on its recent flow and water loss, that this glacier has already begun collapsing / being undermined by sea water. Secondly, they put together some modelling of the melting process and estimate that even without more global warming, this glacier will unload all its water within 200 to 900 years, contributing on its own about 9 feet to higher global sea levels. Naturally, the rest of the glaciers in the world aren't sitting on their hands either, so it is just one more nail in the coffin of our lovely biosphere as it has been for the last few thousand years since the last ice age. And over the last

It is a classic slow-motion, far away, hidden-under-a-pile-of-ice process, particularly ill-suited to our communal forms of decision-making, i.e. politics. While in terms of geology and evolutionary biology, the melting is going at lighting speed, it is glacial in terms of our day-to-day public policy concerns and decision making. So Barack Obama's heroic regulations of vehicle emissions and power plant emissions are pushing against a vast conspiracy of apathy, inertia, greed, and myopia. They are far too little, far too late, though better than nothing. If CO2 were purple, we would naturally be much, much farther along by now.

Earth's CO2 history, inferred from various fossil and geologic data and models. Present time is on the far left. I have added a teal line at about 500 ppm CO2, which is where we will be in 2050, and which exceeds what Earth has seen for the last ~20 million years (the period marked "N" for Neogene).

And the response really has to be at the level of public policy, nationally and globally. Without a carbon tax or regulated cap, and without natural shortages of fossil fuels (which seem to be in much larger supply than the atmosphere can take), any CO2 that one virtuous tree-hugger spares the atmosphere simply reduces the price of fuels, helping some one else to use more. If renewable energy sources reach economic parity with essentially free fossil fuels, this situation may change. But for now, fossil fuels always win on pure, amoral, economics. Any effective solution has to be common across all users, to address this mounting tragedy of the commons.

And what does morality have to do with it? Why are tree-huggers regarded as virtuous? It is not out of sheer asceticism. It is pertinent to note that the most significant metric & consequence of global heating isn't geology, or climatology, or economics ... it is biology. The problem is not that rocks are getting warmer, or that ocean water is getting acidic. And the problem is not, (mostly), that humans will have to move a few miles inland or start growing crops in Siberia. All that can be accommodated, or has no moral consequence. The real problem is that climate heating is destroying our biosphere with increasing thoroughness, leaving only weeds and jellyfish behind.

We have already done a bang-up job of biological destruction, starting with the megafaunal extinctions of the Pleistocene (courtesy of human hunters). The last couple of centuries have seen a new mass extinction event gathering steam, as humans have commandeered the entire arable biosphere as well as rangelands, ocean productivity, and forests. Then we poisoned everything with DDT, radioactivity, and currently the neonicotinoid insecticides. Now we are placing the final nails, driving up temperatures beyond where they have been in millions of years, and shredding whole ecosystems by acidifying the ocean. It is going to be a doozy of an extinction event, up there with the greatest of all time. What seems to us slow motion is just an instant in the tapestry of life's history on earth- an incredibly destructive one.

When you see iconic species trotted out as examples of saving rare species, like pandas, condors, and tigers, you can be pretty sure that they are the walking dead. Their populations are so small and habitats so vestigal that they have lost genetic & ecological viability. Unless enormous amounts of healthy habitat are set aside, (and air conditioned!), they will go fully extinct sooner or later. One of the basic values of humanity has always been an appreciation for the beauty of nature and a recognition of the bonds we share, from its incredibly varied resources to its spiritual sustanance. We are animals, and we are dust, after all. Another basic value has been to provide for our children and the ensuing generations, which constitutes one the basic drives of life. But if we eat & heat their environment now, what will they have left? Even if we manage to keep our world on an even keel in social terms and refrain from incinerating ourselves in a nuclear war, we will, at the current pace, leave them a pale shadow of the nature that we inherited, and that is a deep and depressing shame.


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