From the University of California – Los Angeles
Research also helps unravel the mystery of retreating glaciers in the Pacific Ocean’s western tropics
Using a cutting-edge research technique, UCLA researchers have reconstructed the temperature history of a region that plays a major role in determining climate around the world.
The findings, published online Feb. 27 in the journal Nature Geoscience, will help inform scientists about the processes influencing global warming in the western tropical Pacific Ocean.
The study analyzes how much temperatures have increased in the region near Indonesia, and how ocean temperatures affect nearby tropical glaciers in Papua New Guinea and Borneo. Researchers also evaluated the accuracy of existing climate model predictions for that region. The findings illustrate that the region is very sensitive to climate change and that it has warmed considerably over the last 20,000 years, since the last ice age.
The team chose the specific area examined in the study because it is Earth’s warmest open ocean region and a primary source of heat and water vapor to the atmosphere. As a result, temperature changes there can influence climate not just regionally, but globally.
“The tropical Pacific ocean-atmosphere system has been called a sleeping dragon because of how it can influence climate elsewhere,” said lead author Aradhna Tripati, a UCLA assistant professor in the departments of Earth, planetary and space sciences, and atmospheric and oceanic sciences.
Tripati and her team used a technique known as clumped isotope thermometry, which examines the calcium carbonate shells of marine plankton for subtle differences in the amounts of carbon-13 and oxygen-18 they contain. The researchers analyzed extensive modern and geological datasets, conducted theoretical calculations and examined climate model output. The group discovered that temperatures have changed by about 8 to 10 degrees Fahrenheit (4 to 5 degrees Celsius) over that span — more than scientists had previously thought, and more than most models have estimated.
“Most global climate models underestimate the average temperature variations that the region has experienced,” Tripati said, adding that the other models’ simulations may be incomplete or the models are not sensitive enough.
The UCLA team’s conclusions about temperature changes in the region also imply that there have been major fluctuations in the volume of water vapor in the atmosphere there.
As part of the study, Tripati and her colleagues also investigated what sets the past and present height of glaciers in the tropics, and why they have been retreating. To accurately estimate the height of tropical glaciers and average temperatures at altitude in this region, they found that atmospheric mixing, through a process known as entrainment, needs to be factored in.
“We found that the large amount of ocean warming goes a long way to explaining why glaciers have retreated so much,” said Tripati, a faculty member in the College of Letters and Science and a member of UCLA’s Institute of the Environment and Sustainability. “Throughout the region, they have retreated by close to a kilometer since the last ice age, and are predicted to disappear in the next one to three decades. Previously understanding this large-scale glacial retreat has been a puzzle. Our results help resolve this problem.”
Among the implications of the study are that ocean temperatures in this area may be more sensitive to changes in greenhouse gas levels than previously thought and that scientists should be factoring entrainment into their models for predicting future climate change.
The group has already begun a follow-up study, looking at sediment from Indonesia’s Lake Towuti to develop data that can be used to further improve models of climate and water cycling for the region. Researchers will also look at other places in the tropics, the Western U.S. and China.
Co-authors of the study are Sandeep Sahany, postdoctoral researcher in the department of atmospheric and oceanic sciences, Dustin Pittman, graduate student in the department of atmospheric and oceanic sciences, Robert Eagle, assistant researcher in the department of Earth, planetary and space sciences, Jonathan Mitchell, assistant professor in the departments of Earth, planetary and space sciences and of atmospheric and oceanic sciences, J. David Neelin, professor in the department of atmospheric and oceanic sciences and Luc Beaufort, a research scientist at the Center for Research and Teaching of Environmental Geosciences in Aix-en-Provence, France.
The research was supported primarily by the National Science Foundation.
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Paper: http://www.nature.com/ngeo/journal/v7/n3/full/ngeo2082.html
Modern and glacial tropical snowlines controlled by sea surface temperature and atmospheric mixing
Abstract
During the Last Glacial Maximum, tropical sea surface temperatures were 1 to 3 °C cooler than present1, 2, 3, 4, but the altitude of the snowlines of tropical glaciers5, 6 was lower than would be expected in light of these sea surface temperatures. Indeed, both glacial and twentieth-century snowlines seem to require lapse rates that are steeper than a moist adiabat7, 8. Here we use estimates of Last Glacial Maximum sea surface temperature in the Indo-Pacific warm pool based on the clumped isotope palaeotemperature proxy in planktonic foraminifera and coccoliths, along with radiative–convective calculations of vertical atmospheric thermal structure, to assess the controls on tropical glacier snowlines. Using extensive new data sets for the region, we demonstrate that mean environmental lapse rates are steeper than moist adiabatic during the recent and glacial. We reconstruct glacial sea surface temperatures 4 to 5 °C cooler than modern. We include modern and glacial sea surface temperatures in calculations of atmospheric convection that account for mixing between rising air and ambient air, and derive tropical glacier snowlines with altitudes consistent with twentieth-century and Last Glacial Maximum reconstructions. Sea surface temperature changes ≤3 °C are excluded unless glacial relative humidity values were outside the range associated with deep convection in the modern. We conclude that the entrainment of ambient air into rising air masses significantly alters the vertical temperature structure of the troposphere in modern and ancient regions of deep convection. Furthermore, if all glacial tropical temperatures were cooler than previously estimated, it would imply a higher equilibrium climate sensitivity than included in present models.
Looks like a pretty small and localized sample size:
Figure 1: Sites studied.
Shown are core locations (806B, MD97-2138, V24-109) and mountains that were glaciated at the LGM
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“During the Last Glacial Maximum, tropical sea surface temperatures were 1 to 3 °C cooler than present1, 2, 3, 4, but the altitude of the snowlines of tropical glaciers5, 6 was lower than would be expected in light of these sea surface temperatures. Indeed, both glacial and twentieth-century snowlines seem to require lapse rates that are steeper than a moist adiabat..”
Did they also consider sea level changes. For example, 20K YBP, the sea level was around 140m lower than today, meaning >1C cooler due to the lower air pressure. ?.
John F. Hultquist says guyot.
Nice John, it usually takes me three words to say “you are stupid” I appreciate your quick wit and use of language. While we can discuss guyots, the hawaiian hot spot, subsidcence, tectonics and such if you like. My point is that a subsiding sea mount tends to argue against a rising island. Thus, the question is, if man made climate change has raised the ocean in any substantial way, why are these places (in particular) not sinking under the sea these past 250 or so years. Also, as to Midway island (s), a guyot is a flat topped sea mount. There used to be some discussion about these islands being the remains of subsiding mountains and not neccessarily being flat topped at all but the tips of sinking mountains which have developed coral reefs as either they sank or the sea rose.(or both) as they sailed into the northwest. I don’t mind being wrong as then I know I am learning. But then maybe I am getting cranky in my 7th decade. Sorry for awkward typing as I am nearlly blind.
Berényi Péter says:
March 15, 2014 at 2:36 am
“Come on. During the Last Glacial Maximum, which ended 19 thousand years ago sea level was 130 m lower.”
This is the pearl of this discussion. It suggests at least one other adjustment necessary. Assuming the lower reaches of the glaciers are on a slope of (say) 20 degrees. Bringing the ocean up 130m closer to the glaciers, they should shrink by at least 130/sin 20, which equals 350 m retreat with no change in ocean temps. Also, with the much broader shallows at the lower sea level, I would expect it would be a degree or two higher on this account. See Berényi Péter above re the much larger land mass that existed at these lower sea levels. The paper is a piece of junk. Gosh, don’t you love the internet ready availability of every kind of expert across the world. I have been worrying that this is the next big target of the sinistral distropians.
I am currently working on a photographic project. I have a kitty litter box with a capacity
of 14 pounds of cat crap sand. It is now about half full with 6,000 pennies. When I
finish going through my stash of coins, it will contain 9,996.5 cents.
I am going out of my friggen’ mind counting pennies, but I will take a high resolution dSLR
image of a huge stack of pennies and compare that to the 3.5 cents that represent the
total concentration of Carbon Dioxide in the atmosphere. If volume were weight, this
would result in a difference of 68.54 pounds vs 24/1,000 Lb.
CO2 is a trace level gas. How is it that 3.5 parts per 10,000 could have any effect whatsoever?
My Jr Hi school science teacher taught me better than this!
[One dime on front of hundreds of thousands of pennies? Mod]
Don’t be upsetting those sleeping dragons now . .
Christiana Figueres from the UNFCCC has those pesky dragons under control. She’s already invoked the ancient jaguar goddess Ixchel . . .
http://en.wikipedia.org/wiki/Christiana_Figueres
So they want to attribute the ocean warming to CO2? Good luck with that. Somebody archive their data before NOAA gets at it.
For John H. Hultquist,
Just looked up guyot and if it sticks out of the water, it is NOT a guyot. Actually knew about flat topped UNDERWATER sea mounts. A good place to find lots of swimming things wherever they are found. Also looked up Midway geology and found that two bores drilled in 1965 found volcanic basalt at plus or minus 510 feet below surface. They also showed high elevation (700 ft or more above sea level) snail shells. Seems to be some variation in theory over whether or not there is a single hawaiian hot spot or a series of volcanic sources along the hawaiian mountain range.. Ideas change with time. Sometimes they go from one to 10 and in the end come back to one. I am not smart enough to know anything for certain. But, most happy to “meet” you.
I find in a general sense that people who use lots of big words are more interested in impressions than education. It’s an intellectual oppression, really. Since you used only one word and it’s application was incorrect, I am at a loss to explain your expression of superior knowledge.
Renaldo,
During the LGM the top of Midway would have been nearly 400 feet above sea level and quite a bit colder, accounting for the snail shells.
OK, I will try one last time. The snail shells are from a snail that lives at more than 700 feet above the then (and the now, where found) sea level. They were found more than 500 feet down. Unless my math teacher in 1950 was wrong, that is a 1200 foot, plus diffence in elevation and who knows how much higher than the lowest possible.
A guyot is not an island. A guyot is a SUBMERGED, flat topped sea mount. That would be one that is under water. You can tell it’s an island because you can walk on it. (sarc) You can tell these ones are subsiding because there is phsical evidence as well as geologic theory that it was at one time quite a bit higher (relative to the center of the earth) than it is now. At a minimum, 1200 feet and probably 6 or 7 thousand. The newest of the Hawaiian islands is scheduled to appear in about 100,000 years, give or take. Barring changes in the mantle that is.
The underlying question remains, if human caused global climate change has caused the oceans to rise SO much and SO fast that the world is in danger, how is it that places such as Midway Island(s) which, however slowly, are subsiding and are quite low lying, why is it they are still there? And yes, I know about coral reefs, sand infills and such. Such being the case, the seas are rising at a leisurely pace which should be managable by this allegedly smart ape specie. THAT was the point of my initial post.
All of the hawaiian islands drift first mostley west and then nothwest. as the plate upon which they sit, drifts and sinks. Thus, they subside all along the chain, not withstanding erosion, these past 25 million years, in the case of Midway. Give or take.
I love Warmist logic. Modern global average heat content and atmospheric greenhouse gas concentrations suggest climate sensitivity to CO2 is too high in climate models. Paleoclimate data shows models underestimate past climate variance and the only possible explanation they can think of is that modeled climate sensitivity to greenhouse gases is too low. The Warmists will be stumped over this conundrum for awhile.
I was handing out how to vote cards once at a Federal election. It was freezing only 8 C with a chilling wind blowing and I got a chapped face and wind burn afterwards. The Green volunteer was talking to me, and I mentioned the Medieval mini ice age. He said that had not been confirmed and didn’t exist. He was a science degree holder. What discipline? I replied that I was an archaeology and palaeoanthropologist major and the MIA definitely existed, and had a marked affect on peoples lives particularly the Northern Hemisphere. Wine presses not being used were turned into printing presses. Then I added we are an ice planet, and we are lucky at the moment as we are experiencing a warm period or interglacial. It warms up always before an impending colder period that can last 100s of years. But either way, surface water would be OK but precipitation levels would drop in an ice age as there is less evaporation.