NOAA: Scientists Find 20 Years of Deep Water Warming Leading to Sea Level Rise
Sea-level rise has the potential to reshape the coastal environment. Credit: NOAA)
Scientists analyzing measurements taken in the deep ocean around the globe over the past two decades find a warming trend that contributes to sea level rise, especially around Antarctica.
Greenhouse gases in the atmosphere, such as carbon dioxide, cause heating of the Earth. Over the past few decades, at least 80 percent of this heat energy has gone into the ocean, warming it in the process.
“Previous studies have shown that the upper ocean is warming, but our analysis determines how much additional heat the deep ocean is storing from warming observed all the way to the ocean floor,” said Sarah Purkey, an oceanographer at the University of Washington and lead author of the study.
This study shows that the deep ocean – below about 3,300 feet – is taking up about 16 percent of what the upper ocean is absorbing. The authors note that there are several possible causes for this deep warming: a shift in Southern Ocean winds, a change in the density of what is called Antarctic Bottom Water, or how quickly that bottom water is formed near the Antarctic, where it sinks to fill the deepest, coldest portions of the ocean around much of the globe.
The scientists found the strongest deep warming around Antarctica, weakening with distance from its source as it spreads around the globe. While the temperature increases are small (about 0.03°C per decade in the deep Southern Ocean, less elsewhere), the large volume of the ocean over which they are found and the high capacity of water to absorb heat means that this warming accounts for a huge amount of energy storage. If this deep ocean heating were going into the atmosphere instead – a physical impossibility – it would be warming at a rate of about 3°C (over 5°F) per decade.
“A warming Earth causes sea level rise in two ways,” said Gregory Johnson, a NOAA oceanographer at the Pacific Marine Environmental Laboratory in Seattle, and the study’s co-author. “The warming heats the ocean, causing it to expand, and melts continental ice, adding water to the ocean. The expansion and added water both cause the sea to encroach on the land.”
Sea level has been rising at around 3 mm (1/8 of a inch) per year on average since 1993, with about half of that caused by ocean thermal expansion and the other half because of additional water added to the ocean, mostly from melting continental ice. Purkey and Johnson note that deep warming of the Southern Ocean accounts for about 1.2 mm (about 1/20th of an inch) per year of the sea level rise around Antarctica in the past few decades.
The highly accurate deep-ocean temperature observations used in this study come from ship-based instruments that measure conductivity through salinity, temperature and depth. These measurements were taken on a series of hydrographic surveys of the global ocean in the 1990s through the World Ocean Circulation Experiment and in the 2000s in support of the Climate Variability program. These surveys are now coordinated by the international Global Ship-based Hydrographic Investigations Program.
The study, “Warming of Global Abyssal and Deep Southern Ocean Waters between the 1990s and 2000s: Contributions to Global Heat and Sea Level Rise Budgets,” authored by Sarah G. Purkey and Gregory C. Johnson, will be published in an upcoming edition of the Journal of Climate.
NOAA’s mission is to understand and predict changes in the Earth’s environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources. Find us on Facebook.
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Here is the abstract:
2 NOAA/Pacific Marine Environmental Laboratory, Seattle WA 98115, USA
| Abstract |
|---|
We quantify abyssal global and deep Southern Ocean temperature trends between the 1990s and 2000s to assess the role of recent warming of these regions in global heat and sea level budgets. We compute warming rates with uncertainties along 28 full-depth, high-quality, hydrographic sections that have been occupied two or more times between 1980 and 2010. We divide the global ocean into 32 basins defined by the topography and climatological ocean bottom temperatures and estimate temperature trends in the 24 sampled basins. The three southernmost basins show a strong statistically significant abyssal warming trend, with that warming signal weakening to the north in the central Pacific, western Atlantic, and eastern Indian Oceans. Eastern Atlantic and western Indian Ocean basins show statistically insignificant abyssal cooling trends. Excepting the Arctic Ocean and Nordic seas, the rate of abyssal (below 4000 m) global ocean heat content change in the 1990s and 2000s is equivalent to a heat flux of 0.027 (±0.009) W m−2 applied over the entire surface of the Earth. Deep (1000–4000 m) warming south of the Sub-Antarctic Front of the Antarctic Circumpolar Current adds 0.068 (±0.062) W m−2. The abyssal warming produces a 0.053 (±0.017) mm yr−1 increase in global average sea level and the deep warming south of the Sub-Antarctic Front adds another 0.093 (±0.081) mm yr−1. Thus warming in these regions, ventilated primarily by Antarctic Bottom Water, accounts for a statistically significant fraction of the present global energy and sea level budgets.
Received: February 16, 2010; Revised: July 28, 2010; Revised: August 18, 2010
*Pacific Marine Environmental Laboratory Contribution Number 3524.
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I guess all those underwater volcanos spewing massive amounts of heat into the water have absolutely nothing to do with this. Nothing at all.
@ur momisugly Chris H,
I think you may be right, the 800yr time lag shown in ice core data between raised temps, followed by raised C02 is usually explained by deep ocean warming as a result of the former causing the later.
” . . . over the past two decades find a warming trend that contributes to sea level rise, especially around Antarctica.”
Ah, so that explains the rise in sea ice extent around Antarctica. Hmmmm . . .
“The scientists found the strongest deep warming around Antarctica, weakening with distance from its source as it spreads around the globe. “
Can someone explain in words of one syllable how Antarctica can be “the source” of deep ocean warming? The only sources of heat in that area are some volcanic activity… “Highly sensitive temperature probes moving continuously across the bottom of the volcano revealed signs of geothermal heating of seawater.”
http://www.sciencedaily.com/releases/2004/05/040527235943.htm
so co2 in the atmosphere somehow heats deep ocean water
yeah right
anyway, even if their measurements are accurate, the ocean is rising something like 1.4×10^-6% per year.
better start building that ark. oh, wait. you guys go ahead. i live at 7600ft.
at .o5 mm/year i have roughly 46 million years before i need to start worrying
😉
Considering that sea level rise practically stopped in the last years, I announce the whole article as misleading, based on non-actual data and unfounded speculations.
http://climexp.knmi.nl/data/l3a.png
http://climexp.knmi.nl/data/l2a.png
Dismissed!
So when a Big Nino occurs, doest some that heat escape?-into space?
It will be fascinating to read about their proposed mechanism for how the deep water got warmer — when the sun’s radiation hits only the top-most layer. Perhaps they will say that the Gulf Stream is warmer now, and as it reaches its sinking point near the Arctic that heat eventually reaches the ocean floor.
However, as I recall, that flow rate is rather slow, and the timing is not at all consistent with the “man-made global warming” of the past 35 years. If the deeps are warming now, the cause was likely from hundreds of years ago.
How about it, NOAA? Any mechanism to tell us about?
@Dennis Cooper The UN is ready in case we find some aliens there: http://www.telegraph.co.uk/science/space/8025832/UN-to-appoint-space-ambassador-to-greet-alien-visitors.html
evanmjones said at 9:23 am: “Could the increase in underwater volcanic activity around Antarctica have any measurable effect?”
That’s exactly what crossed my mind as I read this article. Always assuming that there really has been a temperature rise in the deep oceans, then surely a lot more likely cause could be an increase in ocean floor volcanic venting, which could then also lead to the oceans losing some of their CO2 into the atmosphere.
Surely that is a lot more credible than some rather tortured hypothesis based around CO2 indirectly causing the oceans to warm, particularly if this is occuring in the deep oceans rather than as a surface effect – why would atmospheric warming cause the deep oceans to warm before first raising the surface temperature?
Is this Lubchenko woman involved in this? In that case……
“”Greenhouse gases in the atmosphere, such as carbon dioxide, cause heating of the Earth. Over the past few decades, at least 80 percent of this heat energy has gone into the ocean, warming it in the process””
I am beginning to wonder if NOAA release these papers to windup WUWT!
I was under the impression downwelling infrared radiation from CO2, from the
atmosphere no less, is completely absorbed by the first millimeter of the sea
surface thereby increasing surface evaporation which cools the sea surface.
But now the infrared radiation penetrates deeper into the oceans than sunlight.
You learn something new every day since CAGW became fashionable.
The deep ocean is the reason for the “underlying temperature trend”. The earth is cooler than it should be. The only thing preventing it from warming to its equilibrium temperature of 22 C is thermal inertia due to the cold reservoir in the deep oceans. The real question is, “Why did the deep oceans get so cold?”
Richard111 beat me to it.
If the measurements (so long since I could use that word insted of “models” so have to give them marks for that at least) show that deep water has warmed slightly then that is information of value. But attributing it to CO2? Nonsense. As Richard111 pointed out, CO2 radiates in the infrared spectrum which penetrates water to a paper thing depth. Being concentrated in such a thin layer, any energy absorbed by that paper thin layer results in a large temperature increase which in turn results pretty much instant evaporation. Not to mention that even if it didn’t, the average SST of the ocean being about 15 C, it is in a temperature range where warmer water would tend to rise, not sink. With no physical mechanism to move the heat content from CO2 to the depths of the oceans, all they have reported is some interesting data that has no more to do with warming from GHG than it does with the sinking of the Titanic.
John said at 10:07 am
evanmjones said at 9:23 am
I have done several ‘back of envelope’ calculations on volcanic heating of water (a while back) and come up with quite small numbers which may actually be worth revisiting in the light of this.
HelmutU says:
September 26, 2010 at 9:24 am
“One or two years ago the Alfred Wegener Institut in Bremen Germany published their temperature-measurements in the deep waters around the Antarctic und found a cooling of the deep waters. Somebody must be wrong.”
Reported here:
http://www.nature.com/news/2008/080430/full/453015c.html
Representing hundredths of a Watt per Meter Squared. Wow.
Reaching for a strong drink, the climatologist stumbles in the tangles mess of computer cables, printer paper, soda pop cans and pizza boxes, plunging headlong into the recycling bin, where they are found screaming the next day. The diagnosis is worse than previously imagined, the doctor is heard to say.
Recent decadal warming and freshening of Antarctic-derived abyssal waters
Gregory Johnson
NOAA/Pacific Marine Environmental Laboratory, Seattle, WA, USA
IOP Conf. Series: Earth and Environmental Science 6 (2009)
source: http://iopp.fileburst.com/ees/ees9_6_032006.pdf
excerpts:
“The large distances between hydrographic sections, and the fact that they are reoccupied only from decade to decade makes quantification of the contribution of the observed recent abyssal warming to the global heat budget difficult. Quantification of the contribution of the warming and freshening observed to the global sea level rise budget is difficult for the same reasons.”
“Nevertheless, this qualitative analysis suggests that abyssal changes may play some role in global heat and sea level rise budgets.”
[like the image used related to the NOAA story — emphasis added for effect]
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Note: if the “quantification of contribution” was difficult a year ago, what just changed?
While I don’t think the results of this study are significant with respect to CAGW it is interesting and should be accepted for what it is. Namely, we have a great big ‘complex’ ocean on Earth and knowing more about it is a good thing. Further, studying its depths is difficult, time consuming, and expensive. Applause, please.
An issue questioned in some of the comments is how warmth from the surface could get into the ocean depths, insofar as “the hot/cold colored water experiment” [Ray @ur momisugly 8”46 am] (been there – done that; with added salt too) suggests this shouldn’t happen. As WUWT commenters are an inventive bunch, it should be interesting to read of possible physical mechanisms how said transfers might proceed.
I have much to do today but will return with high expectations. Thanks, John
The active sun of the late 20th century allowed the jetstreams and associated clouds to move poleward.
That allowed more solar shortwave into the oceans. That process has now ceased but some of the injected energy is still there.
I have proposed before that during a period of high solar input to the oceans some of that energy remains in the oceans and enters the thermohaline circulation to resurface some 1000 years later hence the climate cycling from MWP to LIA to date.
This paper would appear to support that proposition although a number of contributors tried to tell me trhat the downward mixing of that high solar input was minimal.
It is then somewhat of a lottery as to whether the energy coming out at the other end of that 1000 year oceanic cycling coincides with a period of high or low solar activity with the climate consequences varying accordingly.
Anyway, that extra energy in the oceans is from that higher solar shortwave input and nothing to do with CO2 because CO2 only produces more downward infra red which is immediately negated by faster evaporation.
I would be willing to bet that the amount of water pumped out of underground aquifers each year around the entire planet and added to the ocean is more than glacier retreat is adding.
Also, considering how long the LIA lasted and how short a period since the recovery from that event, I would expect the abyssal oceans to be continuing a recovery in temperature from that event and would expect that to continue for another century or so.
Several others have already commented about deep ocean volcanoes. If there actually is any measurable change in heat content 1,000 meters below the surface a more likely (and obvious) explanation would be underwater volcanism. I instinctively roll my eyes whenever I hear claims of “hidden heat” or (my favorite) “planetary thermal inertia”.
I also have an inherent distrust of a thermometer deployed from a boat that can accurately determine temperature to 0.03 deg C of resolution and that they have 2 decades of such data. The implication is that they measured temperature (from salinity?) just as accurately 20 years ago as they do today.
Color me skeptical. The authors’ conclusions have that distinct odor of desperation about them.
evanmjones said: “Could the increase in underwater volcanic activity around Antarctica have any measurable effect?”
Seems odd that this paper failed to mention an earlier conclusion that the missing heat could not be at depth else we would have noticed it in transit from the surface. Nor is there any discussion of why, of all places, this phenomenon should only exist in the Antarctic “weakening with distance from its source as it spreads around the globe.” As for warming that occurs at depth, but not elsewhere. who knew warm water would sink?
Methinks Dr. Trenberth is a bit too stuck on his prior conclusion that there is some missing heat. Whether that’s true or not, it doesn’t mean that he has found it.
I thought maybe they had already accounted for the missing heat. Section 5.5.3 Chapter 5 of the 4th IPCC report estimates the component of sea level rise due to thermal expansion as 1.6 mm/year (+ or – 0.5 mm) for the decade 1993 to 2003. For the period 1961 thru 2003 the estimate was 0.42 mm/ year (+ or – 0.12 mm). Aside from a mysterious change in the estimate of thermal expansion by a factor of 4 and the dismissal of other possible major contributors to sea level change, such as groundwater mining the analysts are closing the gap between estimates and observed. “Measure it with a micrometer, mark it with a grease pencil and cut it with an axe.” seems to apply.
Reference: Bindoff, N.L., J. Willebrand, V. Artale, A, Cazenave, J. Gregory, S. Gulev, K. Hanawa, C. Le Quéré, S. Levitus, Y. Nojiri, C.K. Shum, L.D.Talley and A. Unnikrishnan, 2007: Observations: Oceanic Climate Change and Sea Level. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
“Nor is there any discussion of why, of all places, this phenomenon should only exist in the Antarctic “weakening with distance from its source as it spreads around the globe.”
I don’t have a problem with that.
If the source of any ‘extra’ deep water energy is solar shortwave input from a period of active sun then the southern hemisphere being mostly water then I would expect the maximum effect south of the equator.
Then the thermohaline circulation takes it for a long tour around Antarctica before moving northward again.
Assuming their observations are correct in the first place (not guaranteed because they are desperate to find some ‘missing heat’) these findings would suit me nicely.