Pause in Sea Level Rise Tied to Massive Flooding in Australia

By Tom Yulsman | August 19, 2013 9:07 pm

This animated gif  shows before and after views of Australia’s Channel Country captured by NASA’s Aqua satellite, the first on September 2009 during relatively dry conditions, and the second on March 2011, when massive flooding occurred. (Image source: LANCE MODIS Rapid Response. Animated gif: Tom Yulsman)

As I noted here earlier in August, human-caused global warming drove sea level to its highest value seen in the satellite record in 2012 — after having fallen very dramatically during an 18-month period starting in 2010.

Now, researchers have uncovered new, significant details about why that happened, along with the key role that Australia played.

To understand what happened, first have a look at the animated gif above.

Click for false-color Landsat image of the Channel Country. (Image: NASA)

I put it together using two images acquired by NASA’s Aqua satellite. The first, captured in September of 2009, shows an inland delta during a relatively dry period in a region of Australia called the Channel Country. The second, acquired in March 2011, shows what happened when three atmospheric patterns came together to drive a gargantuan amount of rain into Australia’s interior. The blue colors represent water, with darker tones indicating deeper water.

What does that have to do with sea level? Here’s where things get interesting.

Researchers had previously tied the drop in sea level to La Niña conditions, which caused an increase in precipitation over some land areas and a concomitant decrease over the oceans. The result was a shift in water from the oceans to the land, and thus a drop in sea level.

In the new research, to be published next month in the journal Geophysical Research Letters, the same scientists have shown that two other semi-cyclic climatic phenomena teamed up with La Niña to drive a huge amount of water from the oceans to the land, and particularly to Australia.

Here’s how it all came together according to the researchers, led by John T. Fasullo of the National Center for Atmospheric Research here in Boulder:

First, La Niña shifted moisture to the western side of the Pacific — toward Australia. Then the Southern Annular Mode helped push that moisture into the interior of Australia, as rain. This resulted in massive flooding. Later, yet more moisture poured into Australia’s interior from the climatic phenomenon known as the Indian Ocean Dipole.

But wouldn’t all that moisture simply have run off into rivers and out into the ocean, resulting in little to no change in sea level? Surprisingly, the answer is no.

That’s because much of Australia’s interior comprises one of our planet’s largest internal drainage systems. And that means when rainfall comes in, water does not go out. At least not out into rivers that drain into the sea. After the 2010 and 2011 floods, some of the water evaporated, and much of it slowly percolated into the desert sands.

To bring things full circle, Fasullo and his colleagues used a variety of tools to piece this complex picture together, including data from NASA’s Grace satellites, which enabled them to track how mass in the form of water shifted from the oceans to Australia.

In their paper, the researchers conclude with this:

Lastly, the current global sea level anomaly is an interesting counterpoint to the 2011 drop, with strongly positive anomalies in mid-2013 accompanying ENSO-neutral conditions.

Translation: Now that La Niña has subsided, and the flooding is long gone, sea level has continued to go up again.

That long-term trend is driven by thermal expansion of ocean waters, and meltwater from Earth’s glaciers and ice sheets rushing into the seas — all a product of a warming world.

One moral of the story is this: If the rise in sea level takes a break again at some point in the future, don’t accept at face value claims that it disproves anthropogenic global warming. Wait for scientists to piece together the complex picture of what’s really happening.

  • Patriotic American

    You have to be kidding me…you expect a rational person to believe that La Nina, rains and floods in Australia caused the Worldwide Sea Level to mysteriously drop!?

    • Tom Yulsman

      Dear Patriotic American:

      You might actually consider reading the entire post while checking your biases at the door. Also, click the link to access the study itself (although without a subscription you may only be able to read the abstract).

      If you were to do that you would learn that the transfer of water from the oceans to the interior of Australia, as well as other landmasses (although Australia was most significant) took place over the course of something like 18 months or more. So this was not some sort of instantaneous effect. And it was documented by a NASA satellite called GRACE that is exquisitely sensitive to changes in gravity induced by the shifting of mass — like the mass of the water that wound up on Australia and other places.

      Concerning rationality, a team of scientists working with the GRACE data, and other kinds of data too, came to their conclusions after rigorous analysis, and they published their work in a highly reputable peer-reviewed scientific journal. So it is no joke. Lastly, the findings, however unbelievable they may sound to you, are supported by the evidence and actually make perfect sense.

      But I suspect none of this will make any difference in the way you think about these and other findings because my guess is that you see the world through a biasing screen of politics, rather than assessing their objectively on their merits.

      • Patriotic American

        Tom, I appreciate your response and sorry it took so long to get back to you. As far as my bias it is based in this crazy thing called common sense. I, as many others in the world, are now very skeptical of the “findings” of “scientists” using “evidence” they collect and use to expand a belief that humans are responsible for the earths “global warming”, and that when this has not been the case the explanations as to why just don’t carry weight in the whole common sense world. I believe in taking care of earth, so let’s be clear on that, I have always been a tread lightly, pack out more than you pack in kind of guy. That being said when reality tells us a different story than what we hear from “experts” and we find out that the models they used were incorrect (all of them, not one was right), then we must question their findings and what they suggest. This is common sense “whenever you eliminate the impossible, whatever remains, no matter how improbable is innevitably the truth.” The truth is the “scientists” don’t know what is going on, and they are reaching far and wide to explain it away and when added to the misinformation provided to support a narrative, I think you can see why we are skeptical.

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ImaGeo

ImaGeo is a visual blog focusing on the intersection of imagery, imagination and Earth. It focuses on spectacular visuals related to the science of our planet, with an emphasis (although not an exclusive one) on the unfolding Anthropocene Epoch.

About Tom Yulsman

Tom Yulsman is Director of the Center for Environmental Journalism and a Professor of Journalism at the University of Colorado, Boulder. He also continues to work as a science and environmental journalist with more than 30 years of experience producing content for major publications. His work has appeared in the New York Times, Washington Post, Audubon, Climate Central, Columbia Journalism Review, Discover, Nieman Reports, and many other publications. He has held a variety of editorial positions over the years, including a stint as editor-in-chief of Earth magazine. Yulsman has written one book: Origins: the Quest for Our Cosmic Roots, published by the Institute of Physics in 2003.

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