Oceanographers have identified a series of ocean hotspots around the world generated by strengthening wind systems that have driven oceanic currents, including the East Australian Current, polewards beyond their known boundaries.
The hotspots have formed alongside ocean currents that wash the east coast of the major continents and their warming proceeds at a rate far exceeding the average rate of ocean surface warming, according to an international science team whose work is published in the journal Nature Climate Change today.
Paper co-author, CSIRO’s Dr Wenju Cai, said that while the finding has local ecological implications in the region surrounding the hotspots, the major influence is upon the ocean’s ability to take up heat and carbon from the atmosphere.
In Australia’s case, scientists report intensifying east-west winds at high latitudes (45º-55ºS) pushing southward and speeding up the gyre or swirl of currents circulating in the South Pacific, extending from South America to the Australian coast. The resulting changes in ocean circulation patterns have pushed the East Australian Current around 350 kilometres further south, with temperatures east of Tasmania as much as two degrees warmer than they were 60 years ago.
“We would expect natural change in the oceans over decades or centuries but change with such elevated sea surface temperatures in a growing number of locations and in a synchronised manner was definitely not expected,” said CSIRO’s Dr Wenju Cai.
“Detecting these changes has been hindered by limited observations but with a combination of multi-national ocean watch systems and computer simulations we have been able to reconstruct an ocean history in which warming over the past century is 2-3 times faster than the global average ocean warming rate,” says Dr Cai, a climate scientist at CSIRO’s Wealth from Oceans Research Flagship.
The changes are characterised by a combination of currents pushing nearer to the polar regions and intensify with systematic changes of wind over both hemispheres, attributed to increasing greenhouse gases.
Dr Cai said the increase of carbon dioxide and other greenhouse gases in the atmosphere has been the major driver of the surface warming of the Earth over the 20th century. This is projected to continue.
He said the research points to the need for a long-term monitoring network of the western boundary currents. In March next year, Australian scientists plan to deploy a series of moored ocean sensors across the East Australian Current to observe change season-to-season and year-to-year.
Lead author of the paper was Dr Lixin Wu, of the Ocean University of China, with contributing authors from five countries, many of whom are members of the Pacific Ocean Panel working under the auspices of the World Meteorological Organisation.
The research was partly funded by a grant from the Australian Climate Change Science Program supported by the Australian Department of Climate Change and Energy Efficiency.
Added 17/2/12
Below are some questions from readers of this post and some answers from Dr Cai. Hope they help.
Q1: This suggests there has been an acceleration in export of equatorial heat to the mid latitudes. Where did it go? Granted land-based measures are sparse in the the southern hemisphere but there are satellite-based measures for more than half the period described indicating trivial to no southern hemispheric warming.
Given that recent research suggests an acceleration in circumpolar winds and a cooling trend in the Antarctic shouldn’t we see significant warming in the mid-latitudes with increased tropical export and reduced polar transport?
Are we merely looking at a simple rearrangement of earth’s thermal furniture rather than a net increase in temperature?
A: It is a combination of both. We see an increase in global ocean averaged temperature as well.
The reason I distinguish this from “global warming” is that the increased circumpolar circulation could be responsible not only for declining Antarctic temperatures but a slowing of thermal egress from the tropics and hence the warmer Tasman.
This rearrangement of the thermal furniture can deliver an increase in surface (sensible) heat without necessarily adding a single joule to the net earth system and thus no “global warming” whatsoever, despite increases in locally measured readings.
A: We have unambiguous evidence showing a net increase in ocean heat content due to global warming.
Don’t believe rearranging heat distribution around the globe can dramatically affect apparent temperature? Check out the global variation demonstrated by El Niño and La Niña phases of the ENSO, all achieved without a massive or even measurable change in incoming solar radiation.
Q2:
Over what period has the study been conducted ?
A: Since 1900. For the first time century-scale trends are calculated showing synchronised warming along major oceanic currents.
Q3:
Here are some thoughts that could add to your considerations
I think the ozone layer/hole and its origin through UV insulation and its influence on high altitude and high latitude winds has a lot to do with this phenomenon.
A: That is right. Over the period since 1979, ozone depletion dominates. However, before 1979, increasing CO2 played a part.
Climate change is probably in the mix , but from my reading, the incoming charged particles (both solar and Cosmic) are driving the ozone formation/ destruction is more fundamental.
This Nature article got me thinking along these lines
http://www.nature.com/nclimate/journal/v1/n1/full/nclimate1065.html
pushing the roaring forties further south is allowing the EAC too move south
Q4:
It seems that almost any weather phenomenon can be attributed by researchers to greenhouse gases, in particular carbon dioxide. No proof is needed! Whatever happened to the scientific method that I learned about many years ago? Over the last 50 years the CO2 content of the atmosphere has increased by 100 ppm. This equates to one ten thousandth part of the atmosphere! Exactly how this can drive the climate has never been demonstrated quantitatively by any scientist. Does anyone think that the great ball of fire in the sky, aka The Sun, could have anything to do with the climate?
Scientists should be starting with the FACTS and deducing their conclusions from them.
A: It is not the percentage of CO2 of the atmosphere that matters. Rather, it is a perturbation to the balance between emission (source) and uptake by the ocean and the terrestrial sinks that matters. When the emission increases, more CO2 stay in the atmosphere, trapping more heat in the atmosphere.
20th February 2012 at 2:17 pm
Editor,
a. Do you know of any plans for such a deployment? Hopefully they will include hydrophones, or maybe the release of more classified data from the navies.
b. Big parenthesis! I’ve largely focussed on the real El Nino/La Nina, as discussed above. That’s a clean-cut situation, and explains the El Nino/ La Nina sequence. With a bit of an extension, it also explains why El Nino is noticed usually at Christmas – and why not at other times.
ENSO is a mish-mash of a poorly understood large-scale weather condition, El Nino, then calling unusual effects in many parts of the globe El Nino also, and adding a non-understood “index” (SOI) measured at Darwin and Tahiti (which is also not the ideal location). BUT SOI is usually a good indicator. The SOI is largely driven by the usually, westward flowing, equatorial current and winds, and this of course gives a gradual drop (years time-frame) in air pressure in the western Pacific, ie Darwin, and therefore SOI. (There are obviously other factors so that this not necessarily a smooth process).
My theory says the increase in undersea eruptions at the East Pacific Rise and Colon Ridge drops the air pressure in that vicinity, stopping the westward flowing wind. The other “ENSO” effects rely on timing of various other interacting events, eg the Vanuatu area events (which lead to the Tasman warming, and heavier rains than usual in Qld).
[I’m sorry for the delay in replying. I’m on the receiving end of a long surgery tomorrow; I won’t be able to reply for a while, at least.]
9th February 2012 at 5:36 pm
It would appear the warm current on the WA Coast has extended futher south also. WA yachts sailing to the Sydney Hobart from WA experienced unusually unseasonal strong headwinds at Cape Naturalist.
9th February 2012 at 3:06 pm
Reply to Editor, 31Jan.
You assume the theory for El Nino, ie a transfer of warm sea from west to east tropical Pacific. Indeed, this should NOT result in an increase in the observed measured Global Warming.
This theory does not match the facts, eg that hot water would need to transfer – unnoticed – several thousand km to its eastern destination! (El Nino actually is noticed as a large pool, several thousand sq km, of sea water heated up to 5C greater than usual and located approximately along the Equator and centred approx 110W.)
It can be better accounted for if there is an injection of heat from below the surface, ie from the Colon Ridge and the East Pacific Rise which sit 2km directly below this heated seawater. (This DOES give an increase in measured Global Warming, and about quantitatively correct.) These Rises are very seismically active, releasing Mantle heat. The heat released from them also accords with the volume of warmed El Nino water. The volcanically heated seawater also explains the fish kill there, due to the liberated toxic hydrogen sulphide – which would not happen if there was a West to East transfer.
What’s this got to do with a heated Tasman Sea? At least 2 things:
a. The El Nino water circulates anticlockwise eventually into that area.
b. The East Pacific Rise is on the eastern side of the Pacific Plate, the other side includes the complicated Vanuatu region which also releases heat, feeding into that Tasman area. (I note that the first 2 huge rain events in Qld last year tied in neatly, ie 10 to 15 days later, with 2 large undersea earthquakes, 7.6 & 7.0 near Vanuatu. The 3rd, Yasi, corresponded to another off the west of Fiji, exactly where there is a fragment of a diverging plate. I also note there’s been another shallow 7.3 off southern Vanuatu again, 02Feb12.)
I’m not aware of any climate/weather models which incorporate undersea seismic activity. (That’s a pity as it explains many more things to that above). The heat derived from such activity has to go somewhere and needs to be acounted for. Yes, I know it’s much smaller than that from the Sun, but geological heat is released irregularly in time and location, so that on occasion it can be quite large – and other times diminished, eg La Nina. That accords well with erratic weather.
[Strictly speaking, the weather events experienced in Qld and elsewhwere in Australia are NOT El Nino or La Nina – which happen off the west coast of South America. Our events often happen at a similar time to the original but they are not the same; they have a similar source. In fact there should be similar events in other oceanic locations – the Carribbean, Indian Ocean near Reunion Islands, ie Indian Ocean Dipole.]
10th February 2012 at 11:46 am
Um… actually no Peter. My reference to ENSO events was in relation to measured earth mean temperature, which rises during El Niño phases and falls during La Niñas.
I believe the surface heating demonstrated locally results from increased stratification and reduced mixing of heavily insolated tropical water with the weakened easterly trades.
I see no evidence of upwelling volcanically heated deep water causing El Niños and what would be your proposed mechanism for La Niña events? Wouldn’t an absence of seismic activity result in neutral conditions if your hypothesis were correct?
10th February 2012 at 3:23 pm
Um … I didn’t realise you had your own renegade theory!
I’m not sure what you mean concerning increased stratification; what is the mechanism? I think your remarks imply a reduced measured global average temperature, due to the stratification hiding its heat, preceding an El Nino. That is not observed. Otherwise, it would be easy to predict an El Nino.
And if your stratification arises from the easterly trades diminishing, what causes the easterly trades to decrease? (The current theory – of a buildup of warm seas to the west – but that would require the winds to actually increase from east to west).
The evidence of volcanic activity is there. As I stated, it includes the fish kill in the El Nino area – and only in that area. This is due to the local volcanically generated H2S, which also produces the “Callao Painter” phenomenon on the local fishing boats during El Nino; this screams “Hydrogen Sulphide” to any chemist. (If one assumes that 1% of the issued magma volume is H2S, that produces a sufficiently strong solution lethal to ocean-going fishes). Additionally, if one does a heat balance of the heat output from the magma issued at those 2 ridges, assuming an El Nino event twice a decade, it matches well the volume of heated water.
[The H2S gradually oxidises to H2SO4 producing acidic solutions quite capable of causing coral bleaching observed in the Great Barrier Reef, which is downstream from Vanuatu. Note that the CO2/H2O system (not H2CO3) has a pKa = 6.38, too high for a small concentration change of CO2 to sensibly shift the ocean water acidity from its pH of 8.1. Sulphuric acid will.]
As I stated in my 4th paragragh, El Nino corresponds to increased activity and magma flow, and La Nina to diminished activity (because the El Nino has released the stress and magma). In between is “normal” activity as the stresses increase again, with attendant small leakages. Most people know seismic activity rarely occurs regulary, indeed, rather like the weather!
13th February 2012 at 9:57 am
Peter, I look forward to reading of deployment of a [relatively] cheap seismic sensor network providing accurate advance notice of El Niño events, a true revolution in seasonal forecasting.
Parenthetically, how exactly is it that your proposed absence of submarine eruptions leads to other than neutral ENSO conditions?