AGU期刊一周Research Spotlight
AGU期刊一周Research Spotlight (Jan 12~Jan 17, 2018)
时间:2018年01月25日 14:32来源: 点击数:

I. Climate Change

1. How Drought Plays Out

Humans are less likely to deplete groundwater when rainfall varies between years.


2. Linking Instrumental and Proxy Data Climate Records

Treatment of the Climatic Signal in Time and Space: From Instrumental and Proxy Data to Modelling; Rouen, France, 18–20 April 2017


II. Hazards & Disasters

1. Preserving a 45-Year Record of Sunspots

Maps reveal how the Sun’s magnetic field evolves through solar cycles.


2. Will Clean Air Fade Away?

Government-sponsored research and regulations enabled western U.S. states to clean up their air, despite industrial and population growth. Proposed funding cuts could undo this progress.


III. Ocean Sciences

1. Rising Ocean Temperatures Threaten Carbon-Storing     Sea Grass

A new model predicts that as ocean temperatures rise, carbon-storing sea grass may disappear and even go extinct in some ecosystems.


IV. Biogeosciences

1. Climate Change Could Leave Big Mark on Earth’s Landscape

The rapid pace of climate change is making it difficult for species to adapt to changes in temperature, water cycles, and other environmental conditions that affect life on Earth, new research finds.


V. Geology & Geophysics

1. Stefan Rahmstorf Receives 2017 Climate Communication Prize

Stefan Rahmstorf was awarded the 2017 Climate Communication Prize at the American Geophysical Union Fall Meeting Honors Ceremony, held on 13 December 2017 in New Orleans, La. The Climate Communication Prize is funded by Nature’s Own, a purveyor of fossils, minerals, and handcrafted jewelry in Boulder, Colo. The prize honors an “AGU member-scientist for the communication of climate science, and highlights the importance of promoting scientific literacy, clarity of message, and efforts to foster respect and understanding of science-based values as they relate to the implications of climate change.”


2. Michael Strasser Receives 2017 Asahiko Taira International Scientific Ocean Drilling Research Prize

Michael Strasser was awarded the 2017 Asahiko Taira International Scientific Ocean Drilling Research Prize at the American Geophysical Union Fall Meeting Honors Ceremony, held on 13 December 2017 in New Orleans, La. The Taira Prize is a partnership between AGU and the Japan Geoscience Union (JpGU) and is made possible through a generous donation from the Integrated Ocean Drilling Program Management International (IOPD-MI). The prize honors an individual for “outstanding transdisciplinary research accomplishment in ocean drilling.”


3. Tony Bartelme Receives 2017 Walter Sullivan Award for Excellence in Science Journalism–Features

Tony Bartelme received the 2017 Walter Sullivan Award for Excellence in Science Journalism–Features at the American Geophysical Union Fall Meeting Honors Ceremony, held on 13 December 2017 in New Orleans, La. The award recognizes “a journalist for a feature story or series in any medium except books that makes information about the Earth and space sciences accessible and interesting to the general public.”


VI. Geophysical Research Letters

1. Widespread Moulin Formation During Supraglacial Lake Drainages in Greenland

Moulins permit access of surface meltwater to the glacier bed, causing basal lubrication and ice speedup in the ablation zone of western Greenland during summer. Despite the substantial impact of moulins on ice dynamics, the conditions under which they form are poorly understood. We assimilate a time series of ice surface velocity from a network of eleven Global Positioning System receivers into an ice sheet model to estimate ice sheet stresses during winter, spring, and summer in a ~30 × 10 km region. Surface-parallel von Mises stress increases slightly during spring speedup and early summer, sufficient to allow formation of 16% of moulins mapped in the study area. In contrast, 63% of moulins experience stresses over the tensile strength of ice during a short (hours) supraglacial lake drainage event. Lake drainages appear to control moulin density, which is itself a control on subglacial drainage efficiency and summer ice velocities.


2. Treating Sample Covariances for Use in Strongly Coupled Atmosphere-Ocean Data Assimilation

Strongly coupled data assimilation requires cross-domain forecast error covariances; information from ensembles can be used, but limited sampling means that ensemble derived error covariances are routinely rank deficient and/or ill-conditioned and marred by noise. Thus, they require modification before they can be incorporated into a standard assimilation framework. Here we compare methods for improving the rank and conditioning of multivariate sample error covariance matrices for coupled atmosphere-ocean data assimilation. The first method, reconditioning, alters the matrix eigenvalues directly; this preserves the correlation structures but does not remove sampling noise. We show that it is better to recondition the correlation matrix rather than the covariance matrix as this prevents small but dynamically important modes from being lost. The second method, model state-space localization via the Schur product, effectively removes sample noise but can dampen small cross-correlation signals. A combination that exploits the merits of each is found to offer an effective alternative.


3. The Global Signature of Ocean Wave Spectra

A global atlas of ocean wave spectra is developed and presented. The development is based on a new technique for deriving wave spectral statistics, which is applied to the extensive ERA-Interim database from European Centre of Medium-Range Weather Forecasts. Spectral statistics is based on the idea of long-term wave systems, which are unique and distinct at every geographical point. The identification of those wave systems allows their separation from the overall spectrum using the partition technique. Their further characterization is made using standard integrated parameters, which turn out much more meaningful when applied to the individual components than to the total spectrum. The parameters developed include the density distribution of spectral partitions, which is the main descriptor; the identified wave systems; the individual distribution of the characteristic frequencies, directions, wave height, wave age, seasonal variability of wind and waves; return periods derived from extreme value analysis; and crossing-sea probabilities. This information is made available in web format for public use at http://www.modemat.epn.edu.ec/#/nereo. It is found that wave spectral statistics offers the possibility to synthesize data while providing a direct and comprehensive view of the local and regional wave conditions.


4. Poleward Shift in Ventilation of the North Atlantic Subtropical Underwater

We report the findings that the sea surface salinity maximum (SSS-max) in the North Atlantic has poleward expanded in recent decades and that the expansion is a main driver of the decadal changes in subtropical underwater (STUW). We present observational evidence that the STUW ventilation zone (marked by the location of the 36.7 isohaline) has been displaced northward by1.2 ± 0.36° latitude for the 34 year (1979–2012) period. As a result of the redistribution of the SSS-max water, the ventilation zone has shifted northward and expanded westward into the Sargasso Sea. The ventilation rate of STUW has increased, which is attributed to the increased lateral induction of the sloping mixed layer. STUW has become broader, deeper, and saltier, and the changes are most pronounced on the northern and western edges of the high-saline core.


5. Decadal Comparisons of Particulate Matter in Repeat Transects in the Atlantic, Pacific, and Indian Ocean Basins

Basin-wide sections of beam cp (proxy for particle concentration) in ocean basins collected during numerous oceanographic programs over the last four decades record variable concentrations in euphotic surface waters, very low concentrations through most of the water column, and very low to very high concentrations near the seafloor. Sections resampled at decadal intervals show that intense benthic nepheloid layers (BNLs) recur in the same general locations in these repeat sections, most often where eddy kinetic energy (EKE: cm2 s?2) is high in overlying waters. Areas beneath regions of low surface EKE consistently have weak to no BNLs. The decadal persistence of the close connection between surface and benthic EKE and presence or absence of BNLs is clear. Understanding the location and causes of intense versus weak BNLs helps in assessing scavenging of adsorption-prone elements in the deep sea and quantifying the impact of deep ocean sediment dynamics on sediment redistribution.


VII. AGU Blogs

1. Scientists monitor volcanic gases with digital cameras to forecast eruptions

Scientists have shown for the first time that volcanoes emit distinctive pulses of gas a few hours before erupting, which could lead to real-time forecasting of dangerous volcanic eruptions that are difficult to predict, according to the researchers.


2. The fascinating Rattlesnake Hills landslide in Washington State

The map indicates a highly complex landslide with what I would consider to be an unusual movement pattern, with displacement apparently approximately parallel to the ridgeline.  This is probably associated with the underlying geological structure, WA DNR interpret it as sliding on a silty layer between fractured basalts, dipping at about 15° into the quarry.  This of course asks questions about how the quarry was permitted in such  geological setting (on the face of it, the setting as described by WA DNR appears to be quite prone to instability), but that is a different issue.


3. Time Scavengers is a web community exploring Earth’s climate and life through deep time

It was a cold, dreary day in December, not even two weeks after the 2016 election. We were two graduate students, Adriane and Jen, and were both down in the dumps, feeling deflated and wondering what direction our country would go in next. More than anything, we were both frustrated with the media, public, and country in general. Furthermore, we were completely discouraged and appalled at the general lack of care and understanding regarding climate change. It was on this December night that Adriane finally decided to present an idea for outreach and education to Jen. From this one text, the education outreach and science communication website Time Scavengers was born.


4. Satellite images of the Montecito debris flows in California

Last week significant debris flows struck the Montecito area of California.  At least 20 people were killed, with a further four people reported as being missing.  The highly mobile flows barreled down three major gullies, the Montecito, San Ysidro, and Romero creeks in the hills to the north of the community.  This area was severely burnt by the Thomas Fire in December.  The vulnerability of the area affected by the fire to landslides had been highlighted in advance.



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