Short-Circuiting Sea Level Rise
- Oct 15, 2014 6:00 am GMT
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Sea level rise can be short-circuited with energy systems that pay for themselves with the power they generate.
The heat of global warming is going principally into the oceans; mainly in the top, mixed, layer of the tropical seas.
One impact of this heat is cyclones that are the main driver of heat towards the poles where it melts icecaps.
Another consequence of this heat is thermal expansion leading to sea level rise and in the short term a third factor, aquifer pumping, is also contributing to sea level rise.
In the long run however, as in the next 1000 years and beyond, the greatest factor will be icecap melting leading to as much as 80 meters of sea level rise.
Kenneth Miller of Rutgers University has pointed out, “The natural state of the earth with present carbon dioxide levels is one with sea levels about 20 meters higher than at present.”
A rise of only half a meter, according to a 2008 OECD study, puts as much as USD 35 trillion in assets in the worlds coastal cities at risk by 2070.
From March 2010 to March 2011 sea levels declined by 5 millimeters due to heavier than normal rainfalls in Australia and the Amazon. This decline was short lived however because the water that originated from the oceans rapidly returned there.
Global warming is predicted to desiccate some regions while others will receive a great deal more precipitation.
In those areas that are going dry residents are pumping aquifers to try to compensate but this is contributing to sea level rise because most of this fossil water ends up flowing back to the ocean. In the estimation of a group lead by Yadu Pokhrel of the University of Tokyo, over the period 1961-2003 aquifer pumping may have contributed as much as 42 percent to the observed sea level rise.
One way to alleviate this situation would be to dam up the excess received in the wet areas and divert some of that to the regions that are drying out. Vis-à-vis California and British Columbia between 60 and 80,000 MW of power could be produced this way or 5 to 7 times the current output of BC Hydro.
On a lifecycle basis hydro is one of the lowest producers of CO2/kWh.
The second law of thermodynamics dictates that heat flows from a hot source to a cold sink and can produce work in the course of transmission.
The poles are colder than the tropics therefore heat migrates from the tropics towards the poles assisted by tropical storms.
There is no way however to harness the forces unleashed by these storms.
The deep seas on the other hand are another cold sink that is currently underutilized and the movement of surface heat to that sink offers the potential to harness much of the energy that othewise would be unleashed in tropical storms.
James Hansen has pointed out, “The rate of ocean heat uptake determines the planetary energy imbalance, which is the most fundamental single measure of the state of Earth’s climate.”
Short-circuiting the movement of heat from the tropics to the poles by diverting it into the deep oceans reduces the long-term risk posed by icecap melting. It also reduces thermal expansion because the coefficient of expansion of sea water declines to a depth of 1000 meters.
Such heat movements would replicate the conditions that are presumed to have brought about the current warming hiatus.
Currently heat diffuses very slowly into the deep ocean because the natural tendency is for heat to rise. It is estimated that it takes about 350 years to migrate naturally to a depth of 1000 meters. This assumption is reinforced by a recent NASA study that shows there has been no measurable warming of the ocean below 2000 meters over the past 8 years.
In contrast, the finding of a team from Lawrence Livermore National Laboratory was the southern seas, since 1970, warmed 24 to 58 per cent more than had been thought and that this was definitive proof the earth is continuing to heat up.
Eco-Business suggests, “One urgent question that needs answering is how much longer the water near the surface can continue to absorb the extra heat which human activities are producing. Another is what will happen when the oceans no longer absorb heat but start to release it. The answers could be disturbing.”
One way to insure the surface continues to absorb heat is to move as much as possible of the accumulating excess into the deep oceans. A heat pipe can do this because it moves heat, rapidly, regardless of the pipes orientation with respect to gravity.
The existing difference in temperature between the ocean’s surface and its depths offers the potential to replace all fossil fuels with as much as 25 terawatts of carbon free ocean energy.
The entities that can capitalize on this potential stand to profit handsomely even as they reslove the climate/energy problem.
The mass of the ocean below the thermocline insures a great deal of heat can be sequestered there absent any appreciable rise in temperature. To 2000 meters it only rose .09C from 1955 to 2010.
Levitus et al. points out however that if this heat were to instantly transferred to the lower 10 kilometers of the atmosphere its temperature would rise on average 36C and we would be cooked. Also there would be a virtual instantaneous rise of ocean levels by 80 meters as all of the icecaps would melt.
Fortunately however this won’t happen because it will take at least 1000 years for the oceans and the atmosphere to come back into equilibrium once we stop adding CO2 to the atmosphere. In that time atmospheric temperature increases will decrease.
But for the heat flowing back from the oceans it would return to preindustrial levels.
In actuality it will reach a new, slightly higher equilibrium temperature due to all of the heat that has already been sequestered in the oceans.
(This article is adapted from a submission to the Simon Fraser University RISE: Ideas Competition on addressing sea level rise}