Archive for November, 2013

Warming the Deep Cold Ocean

Wednesday, November 27th, 2013

The global mean surface temperature has been increasing very slowly, if at all, for the past 10-15 years, even though levels of CO2 emissions continue to rise, sea levels continue to rise, Arctic ice continues to thin, and ocean acidification continues to increase.

Sea level measurements have become increasingly detailed and reliable (epa.gov)

Sea level measurements have become increasingly detailed and reliable (epa.gov)

Since global mean surface temperatures aren’t rising as expected, where has the heat gone?

We have known for a while that about 90% of the extra heat energy absorbed by the Earth goes into warming the seas, which then contribute in complex ways to increasing the global mean surface temperatures. So the missing heat has got to be somewhere in the oceans.

Dense, saline, cold water sinks in the North Atlantic and near the West Antarctic Peninsula, driving the global exchange of water and its heat (wikipedia.org)

Dense, saline, cold water sinks in the North Atlantic and near the West Antarctic Peninsula, driving the global exchange of water and its heat (wikipedia.org)

The slow global circulation of ocean water, known as the Global Conveyor but also as Thermohaline Circulation and more recently as the Meridional Overturning Circulation, plays a huge role in keeping the planet climate relatively stable and in general equilibrium.

What drives this global circulation? Sea water gets denser as it gets colder, reaching its maximum density not at 4 degrees C like freshwater, but at its coldest unfrozen state at -1.8 degrees C. Only in the very highest latitudes, in the North Atlantic and in the Southern Ocean near the West Antarctic Peninsula, does it remain saline enough and get cold and dense enough to sink into abyssal depths in the deep ocean basins 4km or more below the surface.

View from the South Pole of the Global Conveyor or Meridional Overturning Circulation (wikipedia.org)

View from the South Pole of the Global Conveyor or Meridional Overturning Circulation (wikipedia.org)

The sinking of this very cold and saline water drives the global circulation. The deep cold water flows slowly toward lower latitudes, rises or upwells for a variety of reasons and becomes the warmer surface waters, driven into familiar currents by winds and tides.

Very cold saline water (blue) sinks, flows along the basin bottom, is forced toward the surface (green) and then becomes the warm surface current (red) (nature.com)

Very cold saline water (blue) sinks, flows along the basin bottom, is forced toward the surface (green) and then becomes the warm surface current (red)(nature.com)

A great deal of data has now been gathered about the temperatures and salinity levels of ocean waters from all depths around the planet, including from the Southern Ocean that rings the Antarctic. They tell us that the deep ocean water mass around Antarctica, particularly near the West Antarctic Peninsula, is getting warmer and it is freshening. This warming and freshening of the deep cold water has now also been tracked north in all directions to around 30 degrees South latitude.

Deep cold water flows north toward the equator in all the oceans (nature.com)

Deep cold water flows north toward the equator in all the oceans (nature.com)

So that is what has changed. Much of the missing heat, along with West Antarctic glacial melt water, has gone into the deepest, densest, coldest basins of the oceans, rather that into its surface waters.

It will not stay there for long. Further data indicate the mass of the cold dense bottom water is shrinking, and its rate of flow is slowing. These are not reassuring changes.

Still, we have learned that the increasing heat on planet Earth is not only absorbed by surface waters, resulting in a relatively rapid warming of global mean surface temperatures, but that it can also be absorbed first in the high latitudes by very cold water and transported into deeper layers of the ocean. Surface temperatures may then not rise as soon or quickly, but the planet continues to warm anyway, and the long-term impact will be profound.

Ships and satellites are collecting ever more data. If nothing else, the development of this dramatic change in global climate will be incredibly well documented. Perhaps at some point the weight of evidence will be sufficient to push us into effective response.

Meanwhile, last month 140 boats sailed together from San Francisco to the tip of Baja and back. One of the boats first sailed over from Sweden, taking the Northwest Passage to get to the Pacific.

Good Models for Failing EU Fisheries

Monday, November 11th, 2013

The continuing experiment that is the EU ought to be a model of progress for the world, and perhaps in some ways it is, a response to the cries of ‘Never Again’ that rose up at the end of the 2nd World War. But in regulating its fisheries, protecting its fish from over-exploitation, it has clearly failed.

The Exclusive Economic Zone (EEZ) of the european Union is huge, one of the largest, with 25 million square km (wikipedia.org)

The Exclusive Economic Zone (EEZ) of the european Union is huge, one of the largest, with 25 million square km (wikipedia.org)

Still, after decades of efforts, some progress occurred over the past few weeks, resulting in a general ban on discards or bycatch, and greater regulation of individual fisheries to meet the minimum requirements of Maximum Sustainable Yield (MSY) management. Considering the various conflicting needs of so many nations, this is good news.

Atlantic cod stocks are ever closer to oblivion in the North Sea (bbc.co.uk)

Atlantic cod stocks are ever closer to oblivion in the North Sea (bbc.co.uk)

On the other hand, it is a disappointing outcome. It targets a 5% discard rate rather than zero, implemented gradually over the next decade, and some species will still be exempt. It should have banned all deep-water bottom-trawling, but instead proposes not to trawl sites that are identified as particularly vulnerable. Left undecided is how to enforce the new regulations and how to fund the enforcement. Meanwhile subsidies persist for a fleet that is 2-3 times as large as it should be.

Opposition to stronger outcomes came from Spain and France, and from industrial-sized vessels, all of which think they will be harmed even by the limited new regulations: they maintain the changes will happen too quickly, will be too hard to implement, and will be too expensive.

They are wrong. There are quite a few examples elsewhere that the EU could look to.

Atlantic cod - mostly gone from the North-west Atlantic, almost gone from the North Sea, is doing well in the North-east Atlantic (umn.edu)

Atlantic cod – mostly gone from the North-west Atlantic, almost gone from the North Sea, is doing well in the North-east Atlantic (umn.edu)

One is nearby, in Norway, not a member of the EU. Twenty five years ago, in response to dwindling cod stocks, Norway initiated a zero discard policy. More selective gear was used – letting smaller fish escape rather than become bycatch, and some fishing grounds were closed, particularly where the smaller fish were more common. To enforce the ban on discards, vessels have been closely monitored.

The Arctic or Norwegian cod population is in good shape, protected by  tight regulations (imr.no)

The Arctic or Norwegian cod population is in good shape, protected by tight regulations (imr.no)

As fish populations have recovered, catch sizes have increased. Norway also emphasizes ecosystem-based management, science-based decisions on quotas, and precautionary approaches – approaches hard to find in the new EU agreements. And if Norway can do it, so can the EU, as the Norwegians like to point out.

Another example is from the central coast of California. Fishing, including bottom-trawling, pretty well ceased in Moro Bay, south of Monterrey, for all the usual reasons. But then the Nature Conservancy proposed a new approach. With the agreement of the fishermen of Moro Bay, they bought up all the trawl fishing licenses, and the fishermen either left the fishery, or have leased permits back from the Conservancy. The intent – and the outcome – has been to support, yet reduce the level of trawling to a sustainable level, and to try to mitigate its impact.

A brown pelican in Morro Bay celebrates the new fishery regulations there. (flickr.com)

A brown pelican in Morro Bay celebrates the new fishery regulations there. (flickr.com)

And there’s more. In 2005, with the involvement of the fishermen and the Nature Conservancy, the Environmental Defense Fund mediated the designation of 3.8 million acres of coastal waters on the central coast as a no-trawling zone. Not the whole coast but a compromise intended to support fishing, and fishing communities, at a reduced but sustainable level.

Large areas off the central coast of California are now designated as no-trawl zones (edg.org)

Large areas off the central coast of California are now designated as no-trawl zones (edg.org)

The partnership has involved fishermen, community leaders, scientists, and state and federal agencies. This appears to be true co-management. And it is another model that can be exported, if only oppositional lobbyists can be successfully induced to recognize the need to compromise. When the alternative becomes a much wider ban on trawling, compromise is the only option.

We know now that bycatch can be eliminated. Trawling can be limited and regulated. Deep-water trawling can be banned. Enforcement is feasible. Subsidies can be used judiciously, even eliminated. Fleet size can be reduced. Cooperation among all the players is achievable. Ecosystem-based management is possible.

And then fishing is actually sustainable.

So listen up, EU. At stake is the sustainability, the viability of fish stocks in European waters.