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
558 million-year-old fat reveals earliest known animal
21.09.2018 | Max-Planck-Institut für Biogeochemie
Glacial engineering could limit sea-level rise, if we get our emissions under control
20.09.2018 | European Geosciences Union
The building blocks of matter in our universe were formed in the first 10 microseconds of its existence, according to the currently accepted scientific picture. After the Big Bang about 13.7 billion years ago, matter consisted mainly of quarks and gluons, two types of elementary particles whose interactions are governed by quantum chromodynamics (QCD), the theory of strong interaction. In the early universe, these particles moved (nearly) freely in a quark-gluon plasma.
This is a joint press release of University Muenster and Heidelberg as well as the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt.
Then, in a phase transition, they combined and formed hadrons, among them the building blocks of atomic nuclei, protons and neutrons. In the current issue of...
Thin-film solar cells made of crystalline silicon are inexpensive and achieve efficiencies of a good 14 percent. However, they could do even better if their shiny surfaces reflected less light. A team led by Prof. Christiane Becker from the Helmholtz-Zentrum Berlin (HZB) has now patented a sophisticated new solution to this problem.
"It is not enough simply to bring more light into the cell," says Christiane Becker. Such surface structures can even ultimately reduce the efficiency by...
A study in the journal Bulletin of Marine Science describes a new, blood-red species of octocoral found in Panama. The species in the genus Thesea was discovered in the threatened low-light reef environment on Hannibal Bank, 60 kilometers off mainland Pacific Panama, by researchers at the Smithsonian Tropical Research Institute in Panama (STRI) and the Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) at the University of Costa Rica.
Scientists established the new species, Thesea dalioi, by comparing its physical traits, such as branch thickness and the bright red colony color, with the...
Scientists have succeeded in observing the first long-distance transfer of information in a magnetic group of materials known as antiferromagnets.
An international team of researchers has mapped Nemo's genome, providing the research community with an invaluable resource to decode the response of fish to...
21.09.2018 | Event News
03.09.2018 | Event News
27.08.2018 | Event News
21.09.2018 | Physics and Astronomy
21.09.2018 | Life Sciences
21.09.2018 | Event News