Sunlight has more powerful influence on ocean circulation and climate than ice sheets

I senaste numret av Nature 456, 85-88 (6 November 2008) så presenteras en mycket intressant artikel ”Atlantic overturning responses to Late Pleistocene climate forcings” av Lorraine E. Lisiecki (Department of Earth Sciences, Boston University), Maureen E. Raymo och William B. Curry (Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole).

De har studerat ” changes in the North Atlantic deep-water formation during the last four glacial cycles” och vad som har påverkat dessa förändringar.

Slutsats (Surprise! Surprise!):

She explained that the new data changes our understanding about how the different parts of the climate system are interacting with one another and in particular the influence of the ice sheets on climate.

Because the ice sheets are so large, it was a nice simple story to say that they were having the predominant influence on all the parts of the climate system,” said Lisiecki. ”But our study showed that this wasn’t the only important part of the changes in climate. The distribution of sunlight is the controlling factor for North Atlantic deep water formation”.

Yeap! – Det är den där slemma solen igen som ställer till det för alla dessa Global Warming Hysteriker och deras dyrkan av dessa ovetenskapliga dator modeller som bara tar hänsyn till en BRÅKDEL AV ALLA DE FAKTORER SOM PÅVERKAR JORDENS KLIMAT.

Det är nämligen CO2 som orsakar ALLT elände i världendet har nämligen gudarna Al Gore, IPCC och deras redskap klimatmodellerna bestämt.

Och hör sen!

Och apropå havsisen – Den har fördubblats på 50 dagar på Norra halvklotet:

9/20/08: 4.75M square km.

11/9/08: 9.61M square km.

http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

Och detta kommer naturligtvis inte att omnämnas i våra massmedia eller skapa stora rubriker på exempelvis DN och deras ”vetenskaps redaktion” led av Överste Hysterikern och skuldbeläggaren Bojs.

Abstract finns här::

http://www.nature.com/nature/journal/v456/n7218/full/nature07425.html

Deras Pressmeddelande:

http://www.physorg.com/printnews.php?newsid=145202102

Flera som skriver om det: 

http://wattsupwiththat.com/2008/11/09/sunlight-has-more-powerful-influence-on-ocean-circulation-and-climate-than-north-american-ice-sheets/

och

http://alfin2100.blogspot.com/2008/11/sun-proves-embarassment-to-climate.html

och

http://www.sciencecentric.com/news/article.php?q=08110730-sunlight-powerful-influence-ocean-circulation-climate

 

Abstract:

Atlantic overturning responses to Late Pleistocene climate forcings

Lorraine E. Lisiecki1,3, Maureen E. Raymo1 & William B. Curry2

Department of Earth Sciences, Boston University, 675 Commonwealth Avenue, Boston, Massachusetts 02215, USA

Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA

Present address: Department of Earth Science, University of California, Santa Barbara, Santa Barbara, California 93106-9630, USA.

Correspondence to: Lorraine E. Lisiecki1,3 Correspondence and requests for materials should be addressed to L.E.L. (Email: lisiecki@alumni.brown.edu).

 

Top of pageAbstractThe factors driving glacial changes in ocean overturning circulation are not well understood. On the basis of a comparison of 20 climate variables over the past four glacial cycles, the SPECMAP project1 proposed that summer insolation at high northern latitudes (that is, Milankovitch forcing) drives the same sequence of ocean circulation and other climate responses over 100-kyr eccentricity cycles, 41-kyr obliquity cycles and 23-kyr precession cycles. SPECMAP analysed the circulation response at only a few sites in the Atlantic Ocean, however, and the phase of circulation response has been shown to vary by site and orbital band2. Here we test the SPECMAP hypothesis by measuring the phase of orbital responses in benthic 13C (a proxy indicator of ocean nutrient content) at 24 sites throughout the Atlantic over the past 425 kyr. On the basis of 13C responses at 3,000-4,010 m water depth, we find that maxima in Milankovitch forcing are associated with greater mid-depth overturning in the obliquity band but less overturning in the precession band. This suggests that Atlantic overturning is strongly sensitive to factors beyond ice volume and summer insolation at high northern latitudes. A better understanding of these processes could lead to improvements in model estimates of overturning rates, which range from a 40 per cent increase to a 40 per cent decrease at the Last Glacial Maximum3 and a 10-50 per cent decrease over the next 140 yr in response to projected increases in atmospheric CO2 (ref. 4).

 

Department of Earth Sciences, Boston University, 675 Commonwealth Avenue, Boston, Massachusetts 02215, USA

Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA

Present address: Department of Earth Science, University of California, Santa Barbara, Santa Barbara, California 93106-9630, USA.

 

Pressmeddelande:

Sunlight has more powerful influence on ocean circulation and climate than North American ice sheets 

A study reported in today’s issue of Nature disputes a longstanding picture of how ice sheets influence ocean circulation during glacial periods.

The distribution of sunlight, rather than the size of North American ice sheets, is the key variable in changes in the North Atlantic deep-water formation during the last four glacial cycles, according to the article. The new study goes back 425,000 years, according to Lorraine Lisiecki, first author and assistant professor in the Department of Earth Science at the University of California, Santa Barbara.

Lisiecki and her co-authors studied 24 separate locations in the Atlantic by analyzing information from ocean sediment cores. By observing the properties of the shells of tiny marine organisms, called foraminifera, found in these cores, they were able to deduce information about the North Atlantic deep water formation. Scientists can discern historical ocean temperature and circulation patterns through the analysis of the chemical composition of these marine animals.

Previously, scientists relied on a study called ”Specmap,” performed in 1992, to find out how different parts of the climate system interacted with one another during glacial cycles. Specmap analyzed ocean circulation at only one place in the Atlantic.

”What I found was that the one site that the Specmap study used actually didn’t match most of the other sites in the Atlantic,” said Lisiecki. ”They just happened to have a strange site that didn’t behave like most of the other sites. The other sites show that the circulation is not responding to the ice volume, but that it is responding to changes in the distribution of sunlight.”

Previously, scientists believed that deep ocean circulation — the amount of water formed in the North Atlantic that goes into the deep ocean — varied or responded according to the amount of ice volume in the Northern Hemisphere. The prevailing idea was that when ice ages occur, with large sheets of ice over North America, the amount of North Atlantic deep water is reduced.

”That’s an important part of circulation,” said Lisiecki. ”The Gulf Stream brings up warm water from the tropics and that water is turned into this North Atlantic deep water that then sinks and moves southward at depth so you have a cycle. Warm water moves northward and then cools and sinks. That’s the North Atlantic deep water formation process.”

When warm water in the Gulf Stream comes north, it brings heat to the North Atlantic and Europe and then sinks in the North Atlantic and flows back southward at a depth of 3,000 meters.

”This is fairly important for the climate because it brings this heat northward,” said Lisiecki. ”The Specmap study in 1992 found that circulation is reduced when you have large ice sheets — presumably because you have less of this North Atlantic deep water forming. Our results show that this is not always true.”

She explained that the new data changes our understanding about how the different parts of the climate system are interacting with one another and in particular the influence of the ice sheets on climate.

Because the ice sheets are so large, it was a nice simple story to say that they were having the predominant influence on all the parts of the climate system,” said Lisiecki. ”But our study showed that this wasn’t the only important part of the changes in climate. The distribution of sunlight is the controlling factor for North Atlantic deep water formation.

”Our study tells us a lot about how the ocean circulation is affected by changes in climate,” she adds. ”The ocean does not always follow the climate; it exerts its own impact on climate processes. In other words, the ocean circulation doesn’t just follow along with the rest of the climate, it actually changes in different ways than the ice sheets during glacial cycles.”

Source: University of California – Santa Barbara

Läs även andra bloggares åsikter om <a href=”http://bloggar.se/om/milj%F6” rel=”tag”>miljö</a>

Annonser

Etiketter: , , , ,

Ett svar to “Sunlight has more powerful influence on ocean circulation and climate than ice sheets”

  1. North Pole Sea Ice TWICE AS THICK as expected « UD/RK Samhälls Debatt Says:

    […] Sunlight has more powerful influence on ocean circulation and climate than ice sheets […]

Kommentera

Fyll i dina uppgifter nedan eller klicka på en ikon för att logga in:

WordPress.com Logo

Du kommenterar med ditt WordPress.com-konto. Logga ut / Ändra )

Twitter-bild

Du kommenterar med ditt Twitter-konto. Logga ut / Ändra )

Facebook-foto

Du kommenterar med ditt Facebook-konto. Logga ut / Ändra )

Google+ photo

Du kommenterar med ditt Google+-konto. Logga ut / Ändra )

Ansluter till %s


%d bloggare gillar detta: