Jun 2011

The Countdown: 6/2/2011


As promised, more from the pages of Nature tonight.

3… For decades, scientists have attempted to solve the “faint young sun paradox” by proposing higher concentrations of greenhouse gases, specifically carbon dioxide and methane. But a paper last April claimed this wasn’t the case, and that carbon dioxide concentrations were no higher than modern-day values. The authors (Rosing, Bird, Sleep, and Bjerrum) solved the paradox with a cloud-free, ocean-covered Earth that was darker and absorbed more radiation. Well, today Nature printed three separate critiques of the work, and a reply by the authors. If that weren’t enough, the models in the paper and the models in the critiques are inconsistent with temperatures inferred from oxygen isotopes, or from the “molecular time machines” Betül works with. This is why I think the temperature of the early Earth could make for an interesting debate topic here.

2… The climate system has feedbacks in it that can lead to relatively dramatic changes in short amounts of time. One of these feedbacks is related to ocean circulation, which is driven in part by the formation of cold, salty water at the poles. (Cold water is dense. Salty water is dense. Cold, salty water is really dense. It sinks.) Problem is, if you melt ice at the poles, you can release salt-free water (ice isn’t salty), thereby decreasing the density of the water and slowing down ocean circulation. Or so goes the theory. Thanks to a new paper in Paleoceanography, that theory is now better understood. We now know that the source of freshwater is important: specifically, it matters whether the water comes in the form of meltwater or icebergs. This was also the first such model of a freshwater input event 140,000 years ago. (Pervious models have handled more recent events of this type.)

1… When I heard about this, my mouth dropped: Gaetan Borgonie and colleagues discovered “Nematoda from the terrestrial deep subsurface of South Africa.” To put that more clearly: they found worms 3.6 kilometers beneath the Earth. To put it more simply: they found worms in hell. At these depths, temperatures and pressures are very high, and oxygen concentrations are very low. While this subsurface environment has been known to harbor plenty of single-celled life, before this discovery nothing more complex than fungi had ever been found at depths greater than a few hundred meters. Now, we know of an animal that survives at depths of kilometers. Simply stunning.


S. Domagal-Goldman Posted by
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