September 14, 2010
EcoAlert: Ice Sheets Act as Giant Solar Mirrors Controlling Future Climate Change
The giant ice sheets of Antarctica behave like mirrors, reflecting the sun's energy and moderating the world's temperatures. The waxing and waning of these ice sheets contribute to changes in sea level and affect ocean circulation, which regulates our climate by transporting heat around the planet.
Despite their present-day frigid temperatures, the poles were not always covered with ice. New climate records recovered from Antarctica during the recent Integrated Ocean Drilling Program "Wilkes Land Glacial History" Expedition show that approximately 53 million years ago, Antarctica was a warm, sub-tropical environment. During this same period, known as the "greenhouse" or "hothouse" world, atmospheric CO2 levels exceeded those of today by ten times.
Then suddenly, Antarctica's lush environment transitioned into its modern icy realm. In only 400,000 years concentrations of atmospheric carbon dioxide decreased. Global temperatures dropped. Ice sheets developed and Antarctica became ice-bound.
How did this change happen so abruptly and how stable can we expect ice sheets to be in the future?
To answer these questions, an international team of scientists participating in the Wilkes Land Glacial History Expedition spent two months aboard the scientific research vessel JOIDES Resolution in early 2010, drilling geological samples from the seafloor near the coast of Antarctica. Despite negotiating icebergs, near gale-force winds, snow, and fog, they managed to recover approximately 2,000 meters (over one mile) of sediment core.
"These sediments are essential to our research because they preserve the history of the Antarctic ice sheet," observed Dr. Carlota Escutia of the Research Council of Spain CSIC-University of Granada, who led the expedition, along with co-chief scientist Dr. Henk Brinkhuis of Utrecht University in the Netherlands. "We can read these sediments like a history book," Brinkhuis explained. "And this book goes back 53 million years, giving us an unprecedented record of how ice sheets form and interact with changes in the climate and the ocean."
Wilkes Land is the region of Antarctica that lies due south of Australia, and is believed to be one of the more climate-sensitive regions of the polar continent. The new core samples collected during IODP's Wilkes Land expedition are unique because they provide the world's first direct record of waxing and waning of ice in this region of Antarctica.
Combined, the cores tell the story of Antarctica's transition from an ice-free, warm, greenhouse world to an ice-covered, cold, dry "icehouse" world. Sediments and microfossils preserved within the cores document the onset of cooling and the development of the first Antarctic glaciers and the growth and recession of Antarctica's ice sheets. Cores from one site resemble tree rings - unprecedented alternating bands of light and dark sediment preserve seasonal variability of the last deglaciation that began some 10,000 years ago.
Understanding the behavior of Antarctica's ice sheets plays a fundamental role in our ability to build robust, effective global climate models, which are used to predict future climate. "These models rely on constraints imposed by data from the field," the co-chiefs pointed out. "Measurements of parameters such as age, temperature, and carbon dioxide concentration provide invaluable inputs that help increase the accuracy of these models. The more we can constrain the models, the better they'll perform - and the better we can predict ice sheet behavior." [thought the science was already settled]
The science team now embarks on a multi-year process of on-shore analyses to further investigate the Wilkes Land cores. Age-dating and chemistry studies among other analyses are expected to resolve changes in Antarctica's climate over unprecedented short timescales (50-20,000 years).
Data collected from the Wilkes Land expedition will complement previous research from drilling operations conducted elsewhere in the Antarctic over the last 40 years. Together, this research will provide important age constraints for models of Antarctic ice sheet development and evolution, thereby forming the basis for models of future ice sheet behavior and polar climatic change.
Jason McManus via Integrated Ocean Drilling Program Management International and Physorg.com
It doesn't require cognitive dissonance to reconcile past high CO2 with CO2 warming now. On the contrary, it requires you take into account the full body of evidence. Our sun has been steadily warming throughout Earth's history. That means as you go further back in time, the sun was significantly cooler millions of years ago. So the planet was able to enter ice ages at much higher CO2 levels. When you consider the combined effect of sun and CO2 together, you get a close correlation with climate.
ReplyDelete"The sun was significantly cooler" - No. Sunspot activity plays a major role in climate. As you go further back in time, you will see fluctuations in sunspot activity. I see no such thing on "Skeptical Science". There have been periods where the sun had more sunspots, and as a result, was hotter.
DeleteCO2 tends to follow temperature change, not cause it. Better check the physics. Or is that kind of stuff too hard for you?
sorry editor, cognitive dissonance still required, especially in light of the new findings in this post.
ReplyDelete1. These new findings show glaciation starting with CO2 levels 10 times higher than the present (i.e. ~4000 ppm) 53 million years ago when the solar irradiance was close to that of today.
2. The fig 2 on the 'Skeptical Science' site in fact shows the Sun + CO2 'radiative forcing' anomaly to be significantly higher than than average throughout the Ordovician, yet an ice age nonetheless occurred despite no change in the Sun+CO2 forcing.
3. In addition in Fig 2, there was another ice age that began ~30 million years ago when the Sun+CO2 forcing was relatively high.
4. The 4000 ppm CO2 levels 53 million years ago also would invalidate fig 1 on the skeptical science site which indicates CO2 levels were ~1000 ppm 53 million years ago.
5. Young 2009 clearly doesn't have all the answers to this 'paradox' although you wouldn't know that from reading the skeptical science site. Young's paper states that early to middle Ordovician cooling is "problemmatic" and cannot be explained by his volcanic weathering hypothesis.
6. The skeptical science site claims that the last time CO2 levels were this high was 15 million years ago when temps were 5-10F higher. If CO2 was indeed causing radiative forcing, global temperatures should have been approximately the same as today with the same CO2 levels.
etc. etc. and BTW this is only one of many other AGW cognitive dissonances
Q: if CO2 levels were 10 times higher than the present 53 million years ago when solar irradiance was essentially the same as today, and glaciation nonetheless began, why would CO2 levels 10 times less cause an irreversible tipping point now?
ReplyDeleteHere's another for cognitive dissonance lovers:
ReplyDeletehttp://www.physorg.com/news191527326.html
Scientists studying fossils and minerals from Arctic Svalbard, in Norway, have discovered evidence that the ‘greenhouse’ climate of the Cretaceous period was punctuated by a sudden drop in global temperatures.
The findings, which were published in the journal Geology and featured as a highlight in Nature Geoscience, will further contribute to the debate over climate change as they appear to contradict the common model which links high levels of Carbon Dioxide (CO2) - as recorded in the Cretaceous era - with reduced polar ice caps.
Dr Price said: "At certain times in the geological past, the world has been dominated by greenhouse conditions with elevated CO2 levels and warm Polar Regions, and hence, these are seen as analogues of future global climate.
“But this research suggests that for short periods of time the Earth plunged back to colder temperatures, which not only poses interesting questions in terms of how the dinosaurs might have coped, but also over the nature of climate change itself.”
“The flourishing of the dinosaurs and a range of other data indicates that the Cretaceous period was considerably warmer and boasted a high degree of CO2 in the atmosphere,” said Dr Price.
“But over a period of a few hundred or a few thousand years, ocean temperatures fell from an average of 13 degrees centigrade to between eight and four degrees.
“Although a short episode of cool polar conditions is potentially at odds with a high CO2 world, our data demonstrates the variability of climate over long timescales.”
53 million years ago Antarctica was not where it now is. It had recently parted from Africa and was heading south. India was starting to hit Asia on its way north. The Antarctic peninsular has fossil fuels in the form of coal which formed from forests growing before the move south started. It is not totally correct to state that Antarctica was a lush and green land. It was in part but forested by evergreens not tropical forest.
ReplyDeleteThe isthmus of Panama formed about 3 million years ago (with basically same CO2 and solar irradiation as now) which corresponds in time with the start of the present era's cycle of long ice ages and relatively short interglacials. I can't help but think there must be a connection -- consider how much the new isthmus must have disrupted the previous pattern of ocean currents.
ReplyDeleteJohn Marshall,
ReplyDeleteTectonic movements cannot explain the transition from a "hothouse" to an ice sheet over a period of 400,000 years or less
There is some misunderstanding resulting from how the article was written.
ReplyDeleteAntarctica was reasonably warm 53 million years ago, probably frigid in the winter but the snow mostly melted in the summer. It was close to where it is now but it was also still attached to South America and Australia at the time.
Between 33.6 million years ago and 33.5 million years ago, enough separation occured from South America and Australia so that the Antarctic Circumpolar Current started up and Antarctica rapidly glaciated over. It certainly took less than 400,000 years.
CO2 levels were still very high at the time - 1,400 ppm - and CO2 levels stayed high for perhaps another 2 million years after the initial glaciation before starting to fall.
When Antarctica glaciated over, global temperatures dropped by 2.5C (almost certainly because all that ice really does act as like a giant solar mirror, reducing the total amount of solar energy absorbed by the Earth. How much sunlight is reflected and how that would impact temperatures can actually be calculated and the calculation hits the number right on.
Where was Antarctica during the Ordovician Ice Age? Surprisingly not far from where it is now but it was then attached to Africa, South America, Australia, Arabia and India and this whole mini-Super-continent drifted across the South Pole between 460 million to 295 million years ago, just when the Ordivician and Carboniferous ice ages occured. Think big land glaciers at the South Pole, acting like giant solar mirrors.
http://www.eike-klima-energie.eu/climategate-anzeige/eine-illustration-dass-das-co2-die-erde-nicht-in-einem-runaway-tipping-point-roesten-wird/
ReplyDelete