Burns is an expert in reading past climate data from the ratio of oxygen isotopes found in calcite, in speleothems—stalagmites, stalactites and other water-deposited cave features. The ratios indicate seasonal precipitation levels. Burns says data from this study covering approximately 45,000 years agree with modern evidence that the polar jet stream shifts northward in response to climate warming. Further, when the polar jet stream retreats toward the pole, winter precipitation in the Southwest decreases, reducing recharge to underground aquifers.
“We believe this cycle is controlled by the position of the polar jet stream, and that lower moisture levels reach the Southwest from the Pacific Ocean when the climate overall is warmer. Likewise, in periods when the Northern hemisphere’s climate is cooler, the polar jet stream sinks southward and winter rains increase in the desert Southwest, probably in response to advancing glaciers in Northern latitudes,” he says.
Speleothem records collected by Burns and colleagues in New Mexico for this National Science Foundation-supported study are among the first long, high-resolution records of rainfall ever collected for the region.
For such studies, the researchers collect speleothems, in this case stalagmite slices a few inches long from a cave in New Mexico. Speleothems are formed over tens of thousands of years by water seeping through cracks in bedrock and dissolving calcite and aragonite. Depending on temperature, carbon dioxide level and other cave factors, these mineral deposits can precipitate out as stalagmites, stalactites, ribbons, domes or straws.
Analysis of radioactive isotopes and stable oxygen isotopes in the calcite indicate past rainfall over many centuries. “We then try to determine what caused the observed variations at various timescales, from just a few years up to tens of thousands,” Burns says. For the current work, they compared the record with baseline data from Greenland ice cores and with speleothem data from a cave in China, halfway around the world. “This helps to show that the pattern extends across the entire Northern hemisphere,” says Burns.
This relatively new method of oxygen isotope analysis from calcite sampled from ancient speleothems is practiced by only a few research teams worldwide, but it offers more chronological control and is more precise than previous methods that used lake bed sediment records. However, some have questioned its reproducibility, Burns acknowledges. That’s why it was a very pleasant surprise when he and colleagues learned that without any prearrangement between research teams, another team is reporting very similar conclusions in the same journal issue this week, based on speleothem data from a different cave in the Southwest, but using a different laboratory for isotope analyses.
This coincidental but key validation by a completely separate investigating team should go a long way to answer doubts about the reproducibility of climate records from speleothem analysis, says Burns. “Results from our two groups reproduce each other incredibly well, which is a quite exciting and satisfying validation of the overall method.”Stephen Burns
Stephen Burns | Newswise Science News
In times of climate change: What a lake’s colour can tell about its condition
21.09.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)
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21.09.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
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