Earth’s permafrost stores an estimated 20% more organic carbon than is currently in the atmosphere. Permafrost is found along 34% of the planet’s coasts, and this frozen ground erodes at a mean rate of 0.5 meters per year, releasing an estimated 14 billion kilograms of organic carbon.
Despite its major impact, precise contributions of coastal permafrost to carbon cycling remain unclear in certain parts of the Arctic, where rapid warming is likely to increase erosion rates. To address these uncertainties, Couture et al. investigated organic carbon release to the Beaufort Sea due to permafrost erosion along the Yukon Coastal Plain in northwestern Canada.
The researchers collected permafrost soil samples at multiple depths from 22 sites along the coastal bluffs, ensuring that the region’s varying terrain types were represented. They measured the organic carbon content of the samples and determined how much of the soil volume was taken up by large bodies of ground ice. They then used those measurements to calculate the amount of organic carbon stored in permafrost at each site and in areas with similar terrain. The amount of carbon varied according to bluff height and soil composition, with more than half of the soil organic carbon found below the top meter of soil.
To determine how much carbon is released by erosion, the researchers combined their soil organic carbon calculations with long-term erosion rates (the region loses a mean of 0.7 meters of coastline per year). They found that erosion of permafrost releases a total of 36 million kilograms of organic carbon from the Yukon Coastal Plain into the Beaufort Sea annually.
Analysis of carbon isotopes in seabed samples from 14 offshore sites indicated that about 13% of the carbon released by permafrost erosion ends up sequestered in nearshore sediments. The rest is either consumed by organisms in the nearshore environment or transported to the deep ocean.
This research highlights the importance of accounting for large amounts of ground ice that can make up a significant portion of total permafrost volume in some areas. Not accounting for these volumes can result in overestimating soil organic carbon by over 40% at some sites.
These findings contribute to growing knowledge of Arctic coastal dynamics, especially for the Yukon region. They could aid understanding of how carbon cycling in the region may evolve as climate change progresses and help refine predictions of future climate change. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1002/2017JG004166, 2018)
The year 2016 marked a new stage in modern human history: For the first time, the average carbon dioxide (CO2) measurement at Mauna Loa Observatory in Hawaii surpassed 400 parts per million (ppm) for every month of the year. Atmospheric CO2 levels are expected to continue to rise, altering processes in terrestrial environments that have additional feedbacks with Earth’s climate. Accurately representing these land-atmosphere interactions in Earth system models is critical to producing reliable projections but remains a challenge. On 11 August 2017, speakers in the closing Ignite-style session at the Ecological Society of America’s annual meeting presented current and emerging research priorities for Earth system modeling—sharing how empirical and modeling approaches can improve model representations of terrestrial ecosystems. Session presentations and discussions led to two suggestions for achieving this goal.
Suggestion 1: More Data Types, More Details
Earth system models should better quantify and incorporate the impacts of human activity on biophysical (e.g., water and energy) and biogeochemical (e.g., carbon and nitrogen) cycles. Several of the session’s presentations emphasized the importance of improving model depictions of human activities, including fire, agriculture, and logging, and their effects on terrestrial landscapes.
One way to accomplish this goal is to expand the types of data used in model development. For example, model depictions of fire could be improved by incorporating not only quantitative data on human land use, demography, and economics but also qualitative data on human livelihoods that provide further details on human interactions with fire. Developing a database to catalog changes in ecosystem traits by disturbance type—and also disturbance severity and recovery time—could facilitate a new generation of model-data experiments and benchmarks.
Suggestion 2: Better Integration of Empirical and Modeling Approaches
The Earth system modeling community should create and share tools to train Earth system scientists to work at disciplinary interfaces. During the Ignite-style session, attendees expressed interest in understanding how they can apply their field-collected ecological data to Earth system model development.
Training students to use both modeling and empirical approaches will prepare the next generation of scientists to better address challenges in global change science.Speakers detailed their experiences transitioning from empirical ecology to Earth system modeling and emphasized the importance of collecting empirical data in a format useful for evaluating model structure and parameterizations. A central database that aggregates available training opportunities and workshop materials would improve communication between empirical and modeling communities.
The panel also discussed ways to introduce students early in their education to principles and applications of modeling through short exercises in higher education courses. To increase the effectiveness of these types of active learning exercises, we suggest that their impacts on student learning undergo evaluations that are published in peer-reviewed education journals (e.g., CourseSource) so that the evaluations and classroom exercises can be widely accessible to the global change science community. Training students to use both modeling and empirical approaches will prepare the next generation of scientists to better address challenges in global change science.
With these two approaches, the discipline of global change science can maintain its currency and better address existing and emerging research needs in an ever-changing, 400-plus-ppm CO2 world.
The coauthors thank the Ignite-style session speakers for their presentations, which provided inspiration and content for this report. U.S. Department of Agriculture National Institute of Food and Agriculture project 2015-67003-23485 supported the 11 August 2017 Ignite-style session.
—Susan J. Cheng (email: email@example.com), Cornell University, Ithaca, N.Y.; Nicholas G. Smith, Texas Tech University, Lubbock; also at Purdue University, West Lafayette, Ind.; and Alison R. Marklein, Lawrence Berkeley National Laboratory, Berkeley, Calif.; also at University of California, Berkeley
Cobalt is a trace element in the Earth system yet plays an important role in life, being the metal center of vitamin B12, which is crucial to various methyltransferase enzymes. However, there are few rock-forming minerals that incorporate cobalt into their structure, and these are typically found in mafic minerals that are rare in modern silicic continents. Moore et al.  explore the early Earth and find that the weathering rates of the relatively mafic “continents” of the Archean were greater than that of modern silicic continents, and along with low marine sulfur concentrations, were sufficient to keep cobalt bioavailable as a mechanism for carbon fixation and the development of early life.
More modern, non-cobalt based pathways such as photosynthesis may have evolved in response to reduction in cobalt availability. Would these modern processes upon which modern life depends have been possible without the early forms enabled by cobalt and other bioavailable trace metals provided by enhanced Archean mafic weathering? How did the coevolution of rocks and organisms control the development of modern oceans, continents, and life on Earth? These and related questions will need to be further explored in additional studies that build on our emerging understanding of the interacting roles of Archean lithospheric composition, ocean chemistry, and trace elements in the development and evolution of early life.
Citation: Moore, E. K., Hao, J., Prabhu, A., Zhong, H., Jelen, B. I., Meyer, M., Hazen, R. M. & Falkowski, P. G. . Geological and Chemical Factors that Impacted the Biological Utilization of Cobalt in the Archean Eon. Journal of Geophysical Research: Biogeosciences, 123. https://doi.org/10.1002/2017JG004067
Silvertip sharks congregate in large groups potentially numbering in the hundreds in the Chagos Archipelago in the Indian Ocean. Now researchers working in this remote archipelago think they know why. Roughly every 12 hours, tides set in motion waves of cold, dense water that slosh over two of the region’s seamounts. This regular movement transports important nutrients like nitrate up the water column, fueling photosynthesis and biomass production that support marine life ranging from zooplankton to sharks and tuna.
This work highlights how ocean food webs are established, said Elliott Hazen, a marine ecologist at the Southwest Fisheries Science Center in Monterey, Calif., who is not involved in the research. “The aggregation of zooplankton [can] increase foraging opportunities for marine predators.”
A Remote Archipelago
A lot of science is being done to understand this region, given its protected status, but it’s still “massively undersampled,” given its remote location.The Chagos Archipelago, located 500 kilometers south of the Maldives and also known as the British Indian Ocean Territory, is home to a 640,000-square-kilometer marine protected area, the world’s second largest. A lot of science is being done to understand this region, thanks to its protected status, said Phil Hosegood, a physical oceanographer at the University of Plymouth in the United Kingdom, but it’s still “massively undersampled,” given its remote location.
Hosegood and his collaborators recently completed fieldwork around two seamounts known as Sandes and Swart, both with summits roughly 70 meters below the sea surface, to determine why the mountains’ vicinity is such a hot spot for top predators. “There are loads of sharks around Sandes and Swart,” said Hosegood.
Sloshing Delivers Nutrients
With funding from the Bertarelli Foundation, the team installed a roughly 65 meter long mooring dotted with instruments on the flank of Sandes in 2015. The next year, the researchers placed the mooring on the top of Swart. These instruments measured current, temperature, and particles suspended in the water column. The researchers found that cold, nutrient-rich water driven by tides periodically sloshes up the flanks of the seamounts, delivering chemicals like nitrate that phytoplankton consume.
Because the summits of Sandes and Swart are both located in the so-called euphotic zone—a shallow layer from the sea surface downward that receives enough light to permit photosynthesis—this delivery is particularly efficient at promoting the growth of phytoplankton that animals like zooplankton and fish then feed on, said Hosegood, who reported these results last month at the 2018 Ocean Sciences Meeting in Portland, Ore.
Confined by Rock
At the same time, the presence of Sandes and Swart bolsters the local food chain in yet another way, the researchers found. In the open ocean, zooplankton typically migrate several hundred meters each day, moving up and down in the water column: During the daytime, they move down into the darkness of the deep water to escape being seen by predators, and they move back up the water column at night.
“We want to understand the role that these seamounts may have in sustaining shark populations.”But zooplankton like copepods floating above Sandes and Swart can’t go very deep, noted Hosegood. “Unfortunately for them they’re over a seamount.” These trapped zooplankton—observed by the scientists in a roughly 10 meter thick layer of water stirred upward by the tides—make a ready meal for small fish. Those, in turn, become food for larger predators. “Sandes and Swart do have some special properties, from an environmental perspective, that clearly make them an attractive location for sharks,” said Hosegood.
There are likely other localized hot spots of biodiversity in the Chagos Archipelago, Hosegood said, and he and his team hope to return to the Indian Ocean to study them. “We want to understand the role that these seamounts may have in sustaining shark populations.”
Humans have been harnessing fire for millions of years, and today nearly 40% of Earth’s population uses solid fuel like wood, hay, dung, charcoal, and coal to heat their homes and cook their meals. However, breathing in the soot and ash particles that these fuels emit when burned can be harmful. Fine particles—known as PM2.5 since they are, at most, 2.5 micrometers in diameter—are able to travel deep into the lungs. With long-term exposure, they can lead to pneumonia, pulmonary disease, and lung cancer.
Here Kodros et al. study the impact of solid-fuel use on premature death. This topic has been examined extensively, but past studies have primarily looked at PM2.5 exposure within households and in the open air as separate entities, whereas this study considers PM2.5 exposure as a whole. The researchers also tested highly sensitive parameters to show the uncertainty with which premature deaths can be attributed to the use of solid fuels.
The researchers examined data on all deaths across the globe caused by exposure to PM2.5, both in the home and outdoors, during 2015. They used a mathematical model to estimate that PM2.5 exposure from solid-fuel use was responsible for around 2.8 million premature deaths that year. They also found that if they had calculated household and open-air exposure deaths separately, their total estimate would have been about 18% higher—a major difference.
Although combining the two sets of data is an improvement over past studies, the team’s calculations show that the method still has large uncertainties in the relationship between PM2.5 exposure and premature death. The factors that introduced the most uncertainty in their estimates varied by country. For example, in India, China, and Latin America, it is unclear exactly what percentage of the population uses solid fuels for heating and cooking, which directly leads to uncertainties in estimates of deaths attributed to solid-fuel smoke. Conversely, in sub-Saharan Africa, where a known, large percentage of the population uses solid fuels, the uncertainty in the underlying health data (i.e., records of what diseases people died from) is the leading contributor to the uncertainty in the researchers’ estimates.
This study provides a solid reference point for future research looking to improve estimates of deaths attributed to solid-fuel use. In the event that better data become available from these regions, scientists will be better equipped to make more accurate estimates—and help people around the world reduce their exposure to harmful pollutants. (GeoHealth, https://doi.org/10.1002/2017GH000115, 2018)
The Prairie-Pothole Region of North America—a vast expanse of grasslands, or prairies, interspersed with shallow wetlands, or potholes—stretches across Iowa, Minnesota, and the Dakotas in the United States and north through Saskatchewan and Alberta in Canada. These wetland formations, left behind by receding glaciers thousands of years ago, are home to many animal species, including more than half of all migratory waterfowl in North America, and play a key role in controlling flooding by absorbing rain surges, snowmelt, and floodwaters.
The study of how wetlands interact with one another and other water systems is a thriving area of research, especially because it helps inform public policy. For example, the federal Clean Water Act is intended to protect the integrity of “navigable waters”; Clean Water Act regulatory protections have often been interpreted to apply specifically to those wetlands that may affect traditional navigable waters.
To better understand the relationship between wetlands and water flowing into streams, Brooks et al. zeroed in on the Pipestem Creek watershed in North Dakota. The team collected water samples over a 2-year period (2014–2015) in prairie-pothole wetlands and a nearby stream and compared them to data detected by NASA’s Landsat satellite over the same time period.
Chemical signatures left behind by hydrogen and oxygen isotopes during the evaporation process (called isotopic evaporation signals) allowed the researchers to trace back the water’s path. From this, they were able to estimate how much the wetlands collectively contribute to the stream’s flow, as well as how large the water’s surface area would need to be to generate such a signal. Their findings indicated that the wetlands near Pipestem Creek contribute to the stream’s flow throughout the summer and that sections of the stream occasionally become disconnected.
This study demonstrates an innovative new approach to estimating wetlands’ impact on surrounding aquatic systems and tracing the pathways of surface-level water and groundwater. By combining isotopic measurements of water samples collected in the field with satellite data and perhaps incorporating additional types of data, scientists can continue to build a richer understanding of wetland water systems—and hopefully help improve the management of these ecosystems. (Water Resources Research, https://doi.org/10.1002/2017WR021016, 2018)
The second Cargèse school on earthquakes, held last October, covered important and persistently challenging topics in earthquake behavior, including what factors control earthquake nucleation, how static or dynamic stresses and fluid injection trigger earthquakes, and how recent progress in measuring aseismic deformation might inform our understanding.
The 79 participants representing 21 nationalities, mostly Ph.D. students and postdocs, and the 20 lecturers addressed these questions from a range of disciplines and over a range of spatial and temporal scales.
Throughout this school, a recurring topic of discussion was what new insights have been gained since the first school in 2014. Here are some of the new developments presented at the 2017 school.
Recent developments in sensor technology increasingly allow scientists to discern complexity and explore its role in earthquake behavior.Presentations on new observations of the complexity of earthquake rupture—perhaps most notably in the 2016 Kaikoura, New Zealand, earthquake—emphasized the critical role that geometric complexity must play in earthquake physics. With some notable exceptions, earthquake scientists have confronted this complexity only intermittently in the past. However, recent developments in sensor technology, such as nodal-style seismic instruments, remote sensing using interferometric synthetic aperture radar (InSAR), and high-performance computing, increasingly allow scientists to discern complexity and explore its role in earthquake behavior.
Another new development presented at the school arises from multiple studies of large subduction zone earthquakes. These studies point to a preparation phase that manifests as foreshocks and possibly slow slip before some large events, sometimes originating at relatively shallow depths where the fault friction is thought to be high. The question of whether this preparation phase is the manifestation of a cascading failure process or is driven by an underlying aseismic process of unknown origin remains at issue.
Another important contributor to progress, discussed at the school, is the continuing development and application of new signal processing approaches to discern small earthquakes and weak deformation transients. This development is especially significant because the mechanical processes at work in weak deformation transients are poorly known. Laboratory exploration of established and proposed friction laws, of the slip rate–dependent and slip-dependent types, will be essential to elucidate those processes. Lab experiments and numerical simulations are making steady progress toward more realistic physical models that account for such factors as fluids, roughness, and damage zones. These models also provide new insight into earthquake processes.
Induced seismicity fills the spatial gap between laboratory experiments and naturally occurring tectonic earthquakes.Induced seismicity, which was also discussed at the school, provides an opportunity to accelerate progress in understanding the role of fluids in faulting. It also fills the spatial gap between laboratory experiments and naturally occurring tectonic earthquakes. Greater access to data relevant to induced seismicity would help realize its potential for furthering earthquake science in general.
At the end of the school, there were rumblings about the next one. What important current trends might we anticipate? Machine learning and data mining applied to earthquake science are emerging as an important area. Other examples include continued new insights from studies of induced seismicity and potentially even a controlled earthquake experiment. Finally, new observational capabilities—the ramping up of InSAR satellites, lidar surveys, dense seismometer arrays, and novel and highly ambitious deployments like S-net, which spans the seafloor from the Japanese coast to beyond the Japan Trench—are certain to provide new insights and will help ensure that future earthquakes teach us more than has been possible previously.
More information about the school can be found on its website.
—David Marsan, ISTerre, Université Savoie Mont Blanc, Le Bourget du Lac, France; Greg Beroza (email: firstname.lastname@example.org), Department of Geophysics, Stanford University, Calif.; and Joan Gomberg, U.S. Geological Survey, Seattle, Wash.
Researchers report in a new study that they’ve documented rumblings of volcanic thunder for the first time, a feat considered nearly impossible by many volcanologists.
Microphones set out to detect volcanic eruptions in Alaska’s Aleutian Islands recorded sounds of Bogoslof volcano erupting over eight months from December 2016 to August 2017. Researchers analyzing the recordings identified several cracking sounds from eruptions on March 8 and June 10 as volcanic thunder, a phenomenon the study authors said has never before been captured in audio recordings.
Observers have described hearing volcanic thunder in the past, but scientists have been unable to disentangle the booms of thunder caused by volcanic lightning from the cacophony of bellows and blasts that accompany an explosive eruption. In the new study, researchers used microphones on a nearby island and maps of volcanic lightning strokes to identify the sounds of thunder.
“It’s something that people who’ve been at eruptions have certainly seen and heard before, but this is the first time we’ve definitively caught it and identified it in scientific data,” said Matt Haney, a seismologist at the Alaska Volcano Observatory in Anchorage and lead author of the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.
This audio file contains 20 minutes of microphone data recorded during the March 8, 2017 Bogoslof eruption, sped up 60 times. The volcanic thunder sounds are the quick clicks and pops heard throughout, while the sounds of the eruption are the lower-pitched whirring sounds. The eruption ends halfway through, at the 10-second mark, after which the thunder can be heard more clearly. Credit: Matt Haney/Alaska Volcano Observatory & U.S. Geological Survey.
Analyzing volcanic thunder offers scientists a new way of detecting volcanic lightning and potentially a way to estimate the size of an ash plume, according to Jeff Johnson, a geophysicist at Boise State University who was not connected to the new study.
Haney and his team found the intensity of the thunder matched the intensity of the lightning, meaning researchers might be able to use thunder as a proxy for volcanic lightning, Johnson said. The intensity of lightning in a volcanic plume can tell scientists how big the plume is and how hazardous it might be.
“Understanding where lightning is occurring in the plume tells us about how much ash has been erupted, and that’s something that’s notoriously difficult to measure,” Johnson said. “So if you’re locating thunder over a long area, you could potentially say something about how extensive the plume is.”
Monitoring Impending Eruptions
Volcanic eruptions are inherently noisy – explosions of smoke, ash and magma shake the ground and create loud bangs and rumbles that reverberate for miles. Lightning is common in volcanic plumes because particles of ash and ice scrape and collide with each other and become electrified. Researchers assumed volcanic lightning is followed by thunder, as it is during thunderstorms, but they had not yet been able to tease out thunderclaps from the noises of the eruption itself, and many scientists considered it impossible, according to Haney.
In the new study, scientists detected thunder at Bogoslof volcano in Alaska’s Aleutian Islands, a chain of more than 50 volcanic islands in the northern Pacific Ocean.
A closer look at the satellite image of the Bogoslof eruption on May 28. The explosions at the base are called tephra jets, which form when extremely hot volcanic material and gas meet water, transforming into particle-filled clouds of steam. Credit: Dave Schneider/Alaska Volcano Observatory & U.S. Geological Survey.
Researchers constantly monitor the islands from afar for signs of impending eruptions. They use seismic sensors to pick up ground movement before or during an eruption, arrays of microphones to detect sounds of ash exploding skyward and a global network of lightning sensors to detect lightning strokes within an ash plume. Thunderstorms are rare in the Aleutian Islands, so when sensors detect lightning, it most likely means there’s an ongoing eruption, Haney said.
Bogoslof started erupting in December 2016 and erupted more than 60 times through August 2017. Many of the eruptions produced towering clouds of ash more than six kilometers (20,000 feet) high that disrupted air travel throughout the region.
Bogoslof’s eruptions on March 8 and June 10 created ideal conditions for observing volcanic thunder, Haney said. Both eruptions generated immense ash plumes that persisted for several hours after the eruptions ceased. Without the din of an eruption in the background, researchers had a better chance of hearing cracks of thunder caused by lightning in the plume.
A satellite image of Bogoslof volcano on March 11, 2017. The eruption on March 8 produced large changes in the shape and size of the island. The most active vent for the explosive activity is located under the water in the center of the island, and it was greatly enlarged by the March 8 event. The western coastline has grown, and a new vent was produced on the north shore of the island. Credit: Dave Schneider/Alaska Volcano Observatory & U.S. Geological Survey.
Worldwide lightning sensors detected lightning strokes in the ash plumes for several minutes after each eruption ended. In the new study, Haney and his colleagues compared the timing and location of the lightning strokes to sounds recorded by a microphone array on a nearby island.
They found the timing and volume of the sounds the microphones picked up matched the lightning data in a way only thunder could.
On March 8, the microphones recorded at least six distinct bursts of sound that occurred three minutes after lightning activity in the plume peaked. The timing of the bursts means they were almost certainly thunderclaps caused by the lightning: The microphones were 60 kilometers (40 miles) away from the volcano, so it would have taken sound three minutes to reach the microphones. That the thunder was picked up so far away also means it was quite loud, Haney said.
This audio file contains 5 minutes of microphone data recorded during the March 8, 2017 Bogoslof eruption, sped up 10 times. The recording captures thunder from 10:21:30-10:26:30 UTC on March 8, after the eruption had ended. Credit: Matt Haney/Alaska Volcano Observatory & U.S. Geological Survey.
On June 10, the microphones picked up bursts of sound coming from a slightly different direction than sounds from the eruption. The location of the bursts corresponded to areas of peak lightning activity, according to the study.
“If people had been observing the eruption in person, they would have heard this thunder,” Haney said. “I expect that going forward, other researchers are going to be excited and motivated to look in their datasets to see if they can pick up the thunder signal.”
A variety of instruments can be used to gather information about the quantity, type, distribution and composition of precipitation and the potential physical processes underlying its formation. A recent article in Reviews of Geophysics presents a comprehensive review of the data sources and estimation methods of 30 currently available global precipitation datasets. The editors asked one of the authors to explain more about precipitation data and its uses.
What are the different methods of collecting precipitation data, and what are their strengths and weaknesses?
Rain gauges are the most common tools for directly assessing point precipitation at the Earth’s surface. There are several types including accumulation gauges, tipping-bucket gauges, weighing gauges, and optical gauges. Gauge observations provide relatively accurate and trusted measurements of precipitation with long term records. However, gauge measurements provide incomplete areal coverage and are deficient over most oceanic and sparsely populated areas. Moreover, because of the effects of wind speed, evaporation, and precipitation intensity, different types of rain gauge, and observation techniques induce different errors in precipitation measurements.
Another type of ground-level instrument is a disdrometer. Unlike rain gauges, they can detect individual raindrops and measure their size.
Weather radar is an alternative to rain gauges and provides real-time measurements of precipitation with high spatial and temporal resolution, and can also capture the three-dimensional structure of precipitation.
Three ground-based instruments for measuring precipitation. Credit: Sun et al., 2018, Figure 1
Meanwhile, satellite measurements provide precipitation information that is more spatially homogeneous and temporally complete for vast areas of the globe. However, these measurements contain non-negligible random errors and biases owing to the indirect nature of the relationship between the observations and actual precipitation, inadequate sampling, and deficiencies in the algorithms.
How much precipitation data exists?
There are over 30 global precipitation data sets currently available. These can be categorized as gauge-based, satellite-related, and reanalysis data sets.
Products merging satellite and gauge measurements have been designed to improve the accuracy of the measurements. This approach is expected to maximize the relative benefits of each data type; however, these merged products only extend back as far as 1979.
The spatial and temporal resolution of reanalysis data may be heterogeneous. Observational constraints, model parameterizations, and complex interactions between the model and the observations all affect the subsequent precipitation forecast generated by the system. Therefore, the reliability of reanalysis data sets can vary considerably depending on the location and time period.
How do these datasets show different estimates across different temporal scales?
At the annual scale, the precipitation datasets show reasonably consistent interannual variability, although estimates of annual precipitation over global land deviate by as much as 300 mm/year among the different products. Reanalysis data sets show the greatest inconsistency in annual values.
Comparison of the precipitation estimates across global land (left, 1979–2010, 15 data sets) and tropical land (right, 50°S–50°N; 2003– 2010, 19 data sets). The blue, pink and red dots in the represent data sets belonging to gauged-based, satellite-related, and reanalysis products, respectively. Credit: Sun et al., 2018, Figure 7
At the seasonal scale, products that merge satellite and gauge measurements produce low precipitation estimates whereas reanalysis products produce high estimates. The seasonal contributions to the difference in annual precipitation are slightly larger for June-July-August and March-April-May than for the other seasons.
At the daily scale, light precipitation events occur more frequently than other precipitation events, and there is a large divergence in the frequency of light events estimated by the different products. Differences in extreme precipitation estimates are greater for arid regions than humid regions, and for lower latitudes than higher latitudes.
How can precipitation data become more reliable and estimates more accurate?
First, better calibrations of satellite data and better methods for the optimal combination of earth measurements, satellite estimates, and model outputs may provide a better understanding of precipitation. Second, more accurate convective parameterization schemes, reasonable representation of the physical processes, and higher resolution are required in the reanalysis models. Satellite data can be included in the data assimilation to improve the precision of reanalysis estimates. Finally, a single algorithm is not always applicable to different regions, cross-validating the differences among multiple data sets is essential for reducing discrepancies.
What are the potential uses and applications of more accurate precipitation data?
Precipitation is a crucial component of the water cycle and is the most important and active variable associated with atmospheric circulation in weather and climate studies. More accurate and reliable precipitation data would be invaluable, not only for the study of climate trends and variability, but also as inputs to hydrological and ecological models and for model validation, characterization of extreme events, and flood and drought forecasting.
—Chiyuan Miao, Faculty of Geographical Science, Beijing Normal University, China; email: email@example.com
A helicopter from an Argentinean icebreaker plucked four U.S. scientists, a support person, and all their gear from a scientific field camp on an island off the Antarctic coast on Sunday morning after ice and weather conditions prevented a U.S. vessel from retrieving them.
The scientists, who were conducting research funded by the U.S. National Science Foundation (NSF), had completed their paleoclimate field work, they are safe, and they were never in any danger because they had sufficient provisions to last for about 2 more weeks, according to Kelly Falkner, director of NSF’s Office of Polar Programs (OPP).
The incident “did catch the attention of diplomats, and that’s why it rose to a news item.”The incident “did catch the attention of diplomats, and that’s why it rose to a news item,” Falkner told Eos.
A Difficult Combination of Fog and Ice
The four-person research team led by principal investigator Alexander Simms, an assistant professor and sedimentologist in the Department of Earth Science at the University of California, Santa Barbara, was on Joinville Island in the Weddell Sea. There, the scientists were sampling and conducting elevation and ground-penetrating radar surveys of raised beaches to determine their ages and to reconstruct past sea levels and climate.
The U.S. Antarctic Program (USAP) research vessel Laurence M. Gould was expected to collect the scientists from the island. However, it’s not an icebreaker (although it is ice reinforced) and proved unable to safely navigate to the island, Falkner told Eos. “A combination of fog and ice was making it very difficult for [the Gould] to make headway close enough to put Zodiacs”—small motorized boats—“in the water to retrieve people,” she said.
Scientists wait for a helicopter liftoff from Joinville Island. Credit: National Science Foundation
After the USAP requested assistance, the Argentinean icebreaker Almirante Irízar, which had been operating nearby, steamed several hours to pick up the stranded researchers and a fifth person who is an employee of ASC, an NSF support contractor, according to the Argentinean Ministry of Foreign Affairs and Worship.
A Tough Work Environment
“This wasn’t an emergency, but we are very grateful that we can engage with our international partners to take care of situations that could become emergencies.”“Antarctica remains a tough operational work area because of its extreme environment. You can plan for all kinds of things, but you can’t plan for everything,” Falkner said, adding that NSF does a lot of advance and contingency planning and works closely with its international counterparts on a regular basis through the Council of Managers of National Antarctic Programs.
This kind of incident is pretty rare, Falkner said. “This is the first time I have requested such assistance following a camp that NSF put in in my seven years at OPP,” she noted. “This wasn’t an emergency, but we are very grateful that we can engage with our international partners to take care of situations that could become emergencies.”
Carlos Bunge, an adviser to the manager of the Argentinean National Antarctic Program, told Eos from on board the Argentinean icebreaker that the research team on Monday was being transferred to the Gould by Zodiac. The plan is for the Gould to then return to Punta Arenas, Chile, the home port for the ship’s Antarctic operations. Bunge, who has been involved with coordinating science operations with logistical assistance, stressed that this was not a rescue operation. “It was an assistance. They needed to be evacuated from the island. We helped them to get out before the conditions got worse, but there was no risk for human life during the operation. It was just preventing a problematic situation in the future,” Bunge said.
“International cooperation is one of the most important objectives of the Antarctic treaty,” he added. “We all have the same spirit here of research and cooperation.”