Recent interview on environmentalresearchweb regarding new Winckler, et al paper
Recent interview on environmentalresearchweb regarding new Winckler, et al paper http://environmentalresearchweb.org/cws/article/research/33219;
jsessionid=69D426A709D16458584DA96B1113BA3A Mar 5, 2008
Dusting up climate records
To date, records of past dust levels in the equatorial Pacific region have been inconsistent, with some showing a rise in dust levels during interglacial periods and others a dust minimum at those times. Now, measurements generated by researchers at Cornell and Columbia universities in the US for three sites in the Pacific Ocean show dust levels consistently 2.5 times higher during glacial periods than for interglacial times, matching the trend for records from Antarctica.
"Our study provides, for the first time, a quantitative basis for evaluating the role of dust in past climate change and in changes in biogeochemical cycles," Gisela Winckler of the Lamont-Doherty Earth Observatory of Columbia University, US, told environmentalresearchweb. "Our results from a region of heightened climate sensitivity provide a benchmark for the development and testing of new dust models, while also providing vital input for models of climate variability and ocean biogeochemistry."
According to Winckler, observations like the team’s are crucial not only in constraining but also in advancing modern climate models. "On top of that, our records may have implications with respect to large-scale iron fertilization of the ocean," she added.
Wind-borne dust can be a major source of iron while artificial iron fertilization has been suggested as a method of boosting carbon sequestration in the oceans. The idea is that adding iron boosts growth of phytoplankton, which absorb carbon dioxide through photosynthesis and then die, taking the carbon with them as they sink to the ocean depths. But it’s a controversial proposal – it’s not clear how effectively the process would work in practice, and many people are worried about unforeseen effects.
"Accurate reconstruction of dust flux variability in the past may serve as a natural experiment to evaluate the efficacy of fertilization of the ocean through artificial iron addition in the High Nutrient-Low Chlorophyll region of the equatorial Pacific," said Winckler. "While we caution that the idea of iron fertilization is complex and controversial, we believe that assessing the past response to natural variability of iron could enable scientists to develop more quantitative predictions about the possible efficacy of artificial iron addition in the future."
Winckler and colleagues used levels of common thorium (232Th) as a proxy for dust in cores taken from three sites in the Pacific. The sites spanned roughly 6000 miles of the Equator, stretching from a spot near Papua New Guinea to a location off Ecuador’s Galápagos Islands.
"We find remarkable consistency among the three study sites spanning more than a quarter of Earth’s circumference, as well as between tropical regions and the Antarctic, indicating a synchronous response to climate change by interhemispheric dust sources," said Winckler.
The researchers believe that dryer and windier conditions during glacial periods led to increased dust transport.
"Dust is a tremendously interesting component of the climate system, and probably the one we know the least about," said Winckner. "Over the last two decades, scientists have extracted a beautiful record of the variability of dust fluxes to polar regions, mostly from Antarctic ice cores, showing that the world during ice ages was much more dusty than the warm/interglacial world. However, we know much less about low and mid latitudes, where it matters because this is where people live and where probably the engine of the Earth's climate system lies."
The researchers, who reported their work in Sciencexpress, say that the next step is to obtain similar records from critical regions with the goal of providing a "global dust map", both in the present and in the past. Winckner also plans "to continue the path of getting 'observationists' and 'modelers' together – like in our present work".
Abstract of the SciExpress piece:
Covariant Glacial-Interglacial Dust Fluxes in the Equatorial Pacific and Antarctica
Gisela Winckler, Robert F. Anderson, Martin Q. Fleisher, David McGee, Natalie Mahowald
Dust plays a critical role in Earth’s climate system and serves as a natural source of iron and other micronutrients to remote regions of the ocean. We have generated records of dust deposition over the past 500,000 years at three sites spanning the breadth of the equatorial
Pacific Ocean. Equatorial Pacific dust fluxes are highly correlated with global ice volume and with dust fluxes to Antarctica, suggesting that dust generation in interhemispheric source regions exhibited a common response to climate change over late-Pleistocene glacial cycles. Our results provide quantitative constraints on the variability of aeolian iron supply to the equatorial Pacific Ocean and, more generally, on the potential contribution of dust to past climate change and to related changes in biogeochemical cycles.