The researchers' study was published in the May 19 edition of Proceedings of the National Academy of Sciences.
Sediments deposited in large river deltas around the world record information about past sea level, productivity and storminess on the ocean margin, climate on the adjacent continents (including temperatures and precipitation) and human factors that affect sediment delivery to the margin (such as dams and levees), among other things. In addition to these climate factors, Arctic sediments, in particular, could contain records of changes on land due to warming, including permafrost temperature and melting of upland glaciers.
Mead Allison, senior research scientist at The University of Texas at Austin's Jackson School of Geosciences and co-author of the study, said Arctic river deltas have been neglected as records of past climate because the far north is a challenging and expensive environment to work in and it only came to be seen as a bellwether for climate change in the last decade or so.
Arctic river deltas are critical to explore, the researchers reason, because the largest changes in climate are projected for the Arctic. Large amounts of carbon are stored in Arctic permafrost. As those soils thaw, rivers will transport much of their organic carbon to the oceans. As global warming speeds up the melting of shorefast ice (ice attached to the shore), it will likely accelerate coastal erosion from storms, providing a further supply of organic carbon to the coastal zone.
Allison described several ways these sediments could advance scientists' understanding of the global climate system.
They could help answer a hotly debated question about the role of river deltas in the global carbon cycle. Scientists don't know whether large river deltas are a net source or a net sink of carbon. Do they store more carbon than they produce? That's a critical question because carbon dioxide is a major greenhouse gas. Large river deltas are the interface between the land and the oceans and they deliver large amounts of carbon carried along in sediments. As humans alter river systems by adding nutrients from fertilizers, damming water for power and diverting water for drinking and farming, they may be shifting the ability of those systems to fix, burn and store carbon.
"It's a glaring gap in our understanding of the global carbon cycle," Allison said. "It's a potential gotcha in the global climate models. Each river system is different, but we have to get a handle on the net effects."
Arctic river deposits could also confirm the existence of natural climate cycles that climate models need to take into account. For example, there is evidence supporting the existence of a climate cycle called the Arctic Oscillation that affects temperatures, precipitation and storminess at high latitudes. This cycle oscillates over several decades. But because there are only about 50 years of high quality climate data from the Arctic, it's hard to determine to what extent changes now being observed are natural or due to human influence. River delta sediments might allow scientists to reconstruct Arctic climate for thousands of years into the past, and possibly confirm this natural baseline.
Finally, these sediments would establish past climate proxies for specific locations that could be monitored in the future to track the changing climate of the Arctic. If it is a region that will experience the biggest climate changes in this century, it will be important to establish how climate is recorded in sediments.
One advantage of studying margin sediments adjacent to large rivers in the Arctic and elsewhere is that they are deposited at a very high rate. This makes it possible to extract information on a year-to-year basis with high resolution.
The paper "Large-river delta-front estuaries as natural "recorders"of global environmental change" appears in the May 19 Proceedings of the National Academy of Sciences. The lead author is Thomas Bianchi, a professor in Texas A&M University's Department of Oceanography who specializes in estuarine and marine systems. The research was funded by NASA, the Department of Energy, the Office of Naval Research and the National Science Foundation.
Mead Allison | EurekAlert!
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences