Using satellite observations and a suite of climate models, Livermore scientists have found that long-term warming in the upper 700 meters of the Southern Hemisphere oceans has been likely underestimated. “This underestimation is a result of poor sampling prior to the last decade and limitations of the analysis methods that estimate temperature changes in data-sparse regions,” says Livermore oceanographer Paul Durack, lead author of a report in the October 5, 2014, issue of Nature Climate Change. “Our results suggest global ocean warming has been underestimated by 24 to 58 percent. The conclusion agrees with previous studies, but it’s the first time scientists have estimated how much heat we’ve missed.”
The team found that climate models simulating the relative increase in sea surface height—a leading indicator of climate change—between Northern and Southern hemispheres are consistent with highly accurate altimeter observations. However, separating the simulated upper-ocean warming in the Northern and Southern hemispheres is inconsistent with observed estimates of ocean-heat-content change. These sea-level and ocean-heat-content changes should be consistent, suggesting that Southern Hemisphere ocean-heat-content changes were likely underestimated. Since 2004, automated profiling floats (named Argo) have been used to measure global ocean temperatures up to depths of 2,000 meters. The 3,600 Argo floats observing the ocean provide systematic coverage of the Southern Hemisphere and, with earlier data, show gradual warming.
Ocean heat storage is important because it accounts for more than 90 percent of Earth’s excess heat associated with global warming. The Southern Hemisphere oceans make up 60 percent of the world’s oceans. Given that most of the excess heat associated with global warming is in the oceans, this study has significant implications for how scientists view Earth’s overall energy budget.
Contact: Paul Durack (925) 422-5208 (durack1@llnl.gov).
Livermore scientists along with collaborators have created a new type of ion channel consisting of carbon nanotubes (CNTs) inserted into synthetic bilayers and cell membranes to form tiny pores (called porins) that transport water, protons, small ions, and DNA. Collaborators include colleagues from the Molecular Foundry at Lawrence Berkeley National Laboratory, University of California at Merced and Berkeley, and University of the Basque Country in Spain.
Research showed that CNT porins display many behaviors of natural ion channels. The CNT porins spontaneously insert into membranes, switch between metastable conductance states, and display macromolecule-induced blockades. The team also found that local channel and membrane charges could control the ionic conductance and selectivity of the CNT porins. Livermore’s Kyunghoon Kim, a postdoctoral research team member, says, “We expect that CNT porins could be modified with synthetic gates to alter their selectivity.”
“Nanopores are a promising biomimetic platform for developing cell interfaces, studying transport in biological channels, and creating biosensors,” says Aleksandr Noy, a Livermore biophysicist who led the study and is senior author of a paper in the October 30, 2014, issue of Nature. “Many efficient drugs that treat diseases of one organ are quite toxic to another,” says Noy. Unlike taking a pill that is delivered to the entire body, CNTs can help deliver the drug to an area without affecting surrounding organs. These CNT porins have significant implications for the future of health care and bioengineering through drug delivery, novel biosensors, DNA sequencing applications, and as components of synthetic cells.
Contact: Aleksandr Noy (925) 423-3396 (noy1@llnl.gov).
A research team led by Livermore scientists developed a technique for three-dimensional (3D) image processing of a high-speed photograph of a target. “We are interested in how fast-moving surfaces crack, crumble, and disintegrate after they are shocked by a laser pulse, because these details provide us with important information about a material’s properties,” says David Erskine, lead author of a paper in the June 2014 online issue of Review of Scientific Instruments.
Most of the relevant experiments were performed at Livermore’s Jupiter Laser Facility. This technique is particularly applicable in targets that are shocked with lasers, suddenly undergoing intense energy waves. The process described uses an apparatus called VISAR (velocity interferometer system for any reflector) to measure velocities of targets. VISAR is traditionally used to measure a target along a line or at a single point. The team instead used VISAR two-dimensionally to take snapshot images using high-resolution detectors with a short laser flash to freeze target motion. Holographic properties became apparent, making it possible to recover 3D information from 2D images. “We didn’t set out to do holography, but when our target moved, blurring cracks, we were able to refocus the data by numerical processing and bring blurred features into focus,” says Erskine.
“We plan to explore how materials, such as diamond and silicon, fracture and disintegrate when they decompress from high pressure. These fundamental materials can be obtained in high purity and are used in many shock experiments,” says Erskine. “The decompression process provides information about the strength of a material under the conditions encountered in all momentary shock experiments.”
Contact: David Erskine (925) 422-9545 (erskine1@llnl.gov).