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.
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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 would feel a little more comfortable with the trend numbers if there were +/- values associated with them to show the accuracy of the original readings. +0.03K +/- 1.0? +/- 0.1? +/- 0.000001? I suspect the second case is likely the closest to the “truth”. I also doubt that there are sufficient stations for a good representation, but at least this is a step up because it doesn’t state “we modelled the deep-oceanic temperatures and our models gave us the following data…”
Baby steps, Baby steps.
Is 0.053 mm per year, or even 0.093 mm per year a “a statistically significant fraction” of anything that I should be concerned about? I can’t quite see it…..
CAGW Alert: The Western world is boiling all of the plankton in the hydrosphere!
Since when warm water is denser than cold water? Looks like they never did the hot/cold colored water experiment… only NOAA can make changes to the physics of things and understand why things work in reverse in their world!!!
So this study started in 1990s and has been running for less than 20 years? We all agree the 1980 -2000 was a warmer period than say the 1950 – 60s, does anyone know if the water was cooling or warming during these cooler decades?
The sea levels are going up by 1.2mm per year, that is 30 cms per century, hardly liklely to flood London or even the Tuvalu Islands in the liftimes of our grandchildren’s grandchildren, or am I missing something? It certainly leaves us time to imporve our sea walls whilst more studies check the science is correct and validate the causes.
sorry should have written 3.mm per year since 1993
Have they put the cart before the horse? They attribute the deep ocean warming to rising atmospheric CO2. Is it not just as likely that something else caused the deep ocean warming and the CO2 rise simply represents the deep ocean de-gassing?
The post reads, “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.”
Contrary to this, the Ocean Heat Content (OHC) for the top 700 meters of the oceans shows little to no signs of anthropogenic forcing. You simply need to divide the oceans into smaller subsets to see this. The majority of the rises in most of the ocean basins are tied to the significant La Niña events of 1973/74/75/76, and 1995/96, and 1998/99/00/01. Refer to:
http://bobtisdale.blogspot.com/2009/09/enso-dominates-nodc-ocean-heat-content.html
The North Atlantic appears to be impacted by ENSO, the North Atlantic Oscillation (NAO), and AMOC. The surface area of the North Atlantic represents only 15% of the global oceans but it accounts for more than 30% of the rise in OHC since 1955. It is also where most of the drop since 2005 has been occurring.
http://bobtisdale.blogspot.com/2009/10/north-atlantic-ocean-heat-content-0-700.html
And the North Pacific OHC dropped from the late 1960s until the late 1980s, then suddenly rose. The rise coincides with a shift in sea level pressure in the North Pacific:
http://bobtisdale.blogspot.com/2009/12/north-pacific-ocean-heat-content-shift.html
Thank you Mr. Watts. It is kind of interesting.
3rd warming period of the inter-glacial period we are.
Not much concern here at the beach at the moment. I see their point though. I found in the past I have to move the beer cooler from time to time as the sea levels come up.
Thanks for the warning. It could have been a close one.
It boggles the imagination to think that oceanographers can compare temperature measurements made decades apart to within several hundredth’s of a degree C. Remember, these measurements were not made leisurely, with lots of time inside a scientific laboratory using carefully calibrated instruments, but rather thousands of feet down below the ocean surface using thermometers carried remotely by a robot submarine or dangling from a cable dropped over the side of a ship. Amazing!
So far the warming has been far below the 6 ° C rate the alarmists want to use for a doubling of CO2. Since we have had 1/3 of a doubling of CO2 we should have had more than 2 ° C warming we haven’t had this. [.7 ° C is the accepted value and less than ½ of that is from CO2 in the best case.]
To get around this alarmists have speculated that the ”missing heat” is stored in the oceans ! The problem is that since 2005 both atmosphere and the ocean have been cooling.
http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/
Some have SPECULATED that the missing heat may be in the deep parts of the ocean but since they haven’t measured to test this speculation they don’t know. This article claims to have found 20 % of it.
The most important and ignored part of the missing heat controversy is when the heat will return. ?
Since we are only speculating where the heat has gone and have only speculation about how it got there how can we predict how long it will be until it returns ?
Answer: We can’t ! We have a theory of CAGW which DEPENDS upon the “missing heat ” returning in the next 100 years and we don’t know where the heat is and don’t know if or when it will return. Since we cannot find it we cannot measure it so we don’t know much of it exists.
Despite all of this “the debate is over” and we should throw ten’s of trillions of dollars at the nearest politician to make it go away.
It’s NOAA, they’ve just got a little themselves a little confused again.
“Heating” should
daerread “cooling”.Hmmm. “Estimate temperature trends”. Why not “report” temperatures over 20 years or so?
I surely would not find it surprising that some areas within the oceans are heating a bit even as the ocean as a whole undergoes a cooling trend. But I am surprised it is a narrow zone below 4,000 meters near a continental pole that has been cooling slightly for the last 50 years.
On the other hand the absolute insignificance of this estimation is demonstrated by the fact that sea levels during the study period were abnormally stable world wide.
Must chime in to agree with Mike D above. It’s refreshing to see out-in-the-field science actually being done.
“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.”
How can they be certain it’s not +/- 0.0165327 mm/year? My super-calibrated ocean dipstick is reading 0.0536106 mm/year. I think they should remeasure ;o)
Seriously, I’m glad someone is out there on a boat taking measurements instead of modeling the “expected change.”
“Global groundwater levels dwindling: study
‘You will have hunger and social unrest,’ researcher warns”
So, then, here is an example of humans altering sea level; however, it is not because of global warming.
Read more: http://www.cbc.ca/technology/story/2010/09/24/groundwater-study-depletion.html
Is it surprising that the abyssal temperatures are not constant?
If a temperature is rising, extrapolate it out 100 years. Nice and scary.
If it is falling then the warming is just taking a hiatus. Don’t worry, it’ll start warming soon.
“Answer: We can’t ! We have a theory of CAGW which DEPENDS upon the ‘missing heat’ returning in the next 100 years and we don’t know where the heat is…”
I’ll check down the side of the couch.
Mike D in Alberta says: “…at least this is a step up because it doesn’t state “we modelled the deep-oceanic temperatures and our models gave us the following data…””
My BS detector tells me that between these “highly accurate temperature measurements” lies a model.
So warm water sinks? Thermohaline circulation – ur doin it wrong…
Could the increase in underwater volcanic activity around Antarctica have any measurable effect?
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.
Save money, defund NOAA, EPA, and The Dep of Energy. Lets put men on Mars.
NASA should apologize for bad climate science.
Instead they are making it worse.
The post reads, “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.”
It should read: Greenhouse gases in the atmosphere, such as carbon dioxide, should cause heating of the Earth. Over the past few decades, at least 80 percent of this heat energy should have gone into the ocean, warming it in the process. Unfortunately, we can’t find it.
Until now, apparantly. My first reaction was: how did they measure the temperature below the floor of the Argo system. Then I spotted that the used a ship – not a fleet of ships, just a ship – and took the temperature by – measuring differences in salinity.
Is it me, or does this remind anyone of Parkers’ (I think) attempt to show that tropospheric temperatures agreed with surface trends by measuring – wind shear?