AGU 期刊一周Research Spotlights (Jan 13 ~Jan 19, 2016)

发布时间:2017-1-20 10:37:40 点击次数:452

I.Atmospheric Sciences

1. Understanding Causes and Effects of Rapid Warming in the Arctic

A new German research consortium is investigating why near-surface air temperatures in the Artic are rising more quickly than in the rest of the world.

II.Space & Planets

1. Seeking Signs of Life and More: NASA's Mars 2020 Mission

The next Mars rover will be able to land near rugged terrain, giving scientists access to diverse landscapes. It will also cache core samples, a first step in the quest to return samples to Earth.

III.Hydrology, Cryosphere & Earth Surface

1. Using Archives of Past Floods to Estimate Future Flood Hazards

Cross Community Workshop on Past Flood Variability; Grenoble, France, 27–30 June 2016

2. River's Rise Linked to Oklahoma's Largest Earthquake

As human-induced earthquakes increase in frequency and magnitude, researchers race to uncover their effects on surface water and groundwater.

IV. Global Change

1. Report Calls for Revised Method to Chart Cost of Climate Change

Proposed changes could improve the calculation's scientific basis and transparency, according to the report.

V. Ocean Sciences

1. Tsunamis Leave a Telltale Chemical Trail

Researchers follow a trail of organic compounds in soil that reveals the 2011 Tohoku tsunami's path over the Japanese coastline, providing clues to how often tsunamis recur and where they travel.

VI. Geophysical Research Letters

1. Schumann resonances at Mars: Effects of the day-night asymmetry and the dust-loaded ionosphere

Schumann resonances are standing waves that oscillate in the electromagnetic cavity formed between the conducting lower ionosphere and the surface of the planet. They have been measured in situ only on Earth and Titan, although they are believed to exist on other planets like Mars. We report numerical simulations of the Martian electromagnetic cavity, accounting for the day-night asymmetry and different dust scenarios. It has been found that the resonances are more energetic on the nightside, the first resonance is expected to be 9–14 Hz depending on the dust activity and to have low quality factors (Q≃2). This work serves as an input for the upcoming Exomars surface platform (launch 2020), who will attempt to measure them for the first time.

2. Lake seasonality across the Tibetan Plateau and their varying relationship with regional mass changes and local hydrology

The recent growth and deepening of inland lakes in the Tibetan Plateau (TP) may be a salient indicator of the consequences of climate change. The seasonal dynamics of these lakes is poorly understood despite this being potentially crucial for disentangling contributions from glacier melt and precipitation, which are all sensitive to climate, to lake water budget. Using in situ observations, satellite altimetry and gravimetry data, we identified two patterns of lake level seasonality. In the central, northern, and northeastern TP, lake levels are characterized by considerable increases during warm seasons and decreases during cold seasons, which is consistent with regional mass changes related to monsoon precipitation and evaporation. In the northwestern TP, however, lake levels exhibit dramatic increases during both warm and cold seasons, which deviate from regional mass changes. This appears to be more connected with high spring snowfall and large summer glacier melt. The variable lake level response to different drivers indicates heterogeneous sensitivity to climate change between the northwestern TP and other regions.

3. Opal-CT in chert beneath the toe of the Tohoku margin and its influence on the seismic aseismic transition in subduction zones

Thick accumulation of chert is a ubiquitous feature of old oceanic plates at convergent margins. In this study, we investigate chert fragments recovered by the Integrated Ocean Drilling Program expedition 343 at the Japan Trench where the 2011 Tohoku-Oki earthquake (Mw 9.0) occurred. This sample provides a unique opportunity to investigate in situ chert diagenesis at an active subduction margin and its influence on the kinematics of megathrust faulting. Our mineralogical analyses revealed that the chert is characterized by hydrous opal-CT and may therefore be highly deformable via pressure solution creep and readily accommodate shear strain between the converging plates at driving stresses of kilopascal order. As chert diagenesis advances, any further deformation requires stresses of >100 MPa, given the increasing transport distances for solutes as represented in cherts on land. The chert diagenesis is thus related to the mechanical transition from a weakly to strongly coupled plate interface at this margin.

4. Impacts of the QBO on the North Atlantic and Mediterranean storm tracks: An energetic perspective

Impacts of the quasi-biennial oscillation (QBO) on the energetics of the North Atlantic and Mediterranean storm tracks are discussed. The daily National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data for the period 1953–2015 are used to evaluate the spatial distribution of eddy kinetic energy (EKE) and the main factors involved in generation, conversion, and propagation of the EKE in the westerly and easterly phases of the QBO. Results are presented for both early and late winter to uncover intraseasonal variations of the impact. It is shown that the QBO exerts a marked influence on the Mediterranean storm track in early winter, which is of the same order of its impact on the North Atlantic storm track. Further, the impact on the Mediterranean storm track is rather local in early winter but more influenced by variations in the North Atlantic storm track in late winter.

5. Ca isotopic geochemistry of an Antarctic aquatic system

The McMurdo Dry Valleys, Antarctica, are a polar desert ecosystem. The hydrologic system of the dry valleys is linked to climate with ephemeral streams that flow from glacial melt during the austral summer. Past climate variations have strongly influenced the closed-basin, chemically stratified lakes on the valley floor. Results of previous work point to important roles for both in-stream processes (e.g., mineral weathering, precipitation and dissolution of salts) and in-lake processes (e.g., mixing with paleo-seawater and calcite precipitation) in determining the geochemistry of these lakes. These processes have a significant influence on calcium (Ca) biogeochemistry in this aquatic ecosystem, and thus variations in Ca stable isotope compositions of the waters can aid in validating the importance of these processes. We have analyzed the Ca stable isotope compositions of streams and lakes in the McMurdo Dry Valleys. The results validate the important roles of weathering of aluminosilicate minerals and/or CaCO3 in the hyporheic zone of the streams, and mixing of lake surface water with paleo-seawater and precipitation of Ca-salts during cryo-concentration events to form the deep lake waters. The lakes in the McMurdo Dry Valleys evolved following different geochemical pathways, evidenced by their unique, nonsystematic Ca isotope signatures.

6. Defining the ecologically relevant mixed-layer depth for Antarctica's coastal seas

Mixed-layer depth (MLD) has been widely linked to phytoplankton dynamics in Antarctica's coastal regions; however, inconsistent definitions have made intercomparisons among region-specific studies difficult. Using a data set with over 20,000 water column profiles corresponding to 32 Slocum glider deployments in three coastal Antarctic regions (Ross Sea, Amundsen Sea, and West Antarctic Peninsula), we evaluated the relationship between MLD and phytoplankton vertical distribution. Comparisons of these MLD estimates to an applied definition of phytoplankton bloom depth, as defined by the deepest inflection point in the chlorophyll profile, show that the maximum of buoyancy frequency is a good proxy for an ecologically relevant MLD. A quality index is used to filter profiles where MLD is not determined. Despite the different regional physical settings, we found that the MLD definition based on the maximum of buoyancy frequency best describes the depth to which phytoplankton can be mixed in Antarctica's coastal seas.

7. Divergent surface and total soil moisture projections under global warming

Land aridity has been projected to increase with global warming. Such projections are mostly based on off-line aridity and drought metrics applied to climate model outputs but also are supported by climate-model projections of decreased surface soil moisture. Here we comprehensively analyze soil moisture projections from the Coupled Model Intercomparison Project phase 5, including surface, total, and layer-by-layer soil moisture. We identify a robust vertical gradient of projected mean soil moisture changes, with more negative changes near the surface. Some regions of the northern middle to high latitudes exhibit negative annual surface changes but positive total changes. We interpret this behavior in the context of seasonal changes in the surface water budget. This vertical pattern implies that the extensive drying predicted by off-line drought metrics, while consistent with the projected decline in surface soil moisture, will tend to overestimate (negatively) changes in total soil water availability.


1. Scientists try to mitigate methane, from cows

Many creatures, including you and me, emit methane from time to time. Microbes within our guts break down one substance and turn it into another, making methane in the process. Northern lakes and tundra plants also leak methane. That gas, too, is from microbes, which become more active as the air warms.

2. Changing atmospheric conditions may contribute to stronger ocean wave activity on the Antarctic Peninsula

A new study provides important details on the extent of sea ice, which can protect ice shelves from the impacts of ocean storms, in the Antarctic Peninsula.

3. Mount Sulzer – a series of dramatic, and extremely large, debris and ice avalanches

Michael Loso of Wrangell-St. Elias National Park and Preserve in Alaska has kindly provided details of an amazing series of debris and ice avalanches that have descended from the flanks of Mount Sulzer in recent years. The Google Earth image below shows the location.  On the left is the site of these major landslides.  The next valley to the west (on the right in this image) has also suffered a glacier surge in the 2015-16 period, but that is not the focus here.

4. Future shock – the failure to learn from the 2015 earthquake in Nepal

The Nepali Times had a large piece over the weekend entitled Future Shock, which was driven by National Earthquake day in Nepal.  In an accompanying editorial, the newspaper notes the disastrous failure of Nepal to learn lessons from the earthquake.

5. The Most Beloved Weather Forecast You’ve Never Heard About

If you are reading this from the UK, you know already know what this post is about, but to those outside the UK, the “Shipping Forecast” is mostly unknown.  It’s far more than a weather forecast, it’s an institution, with many more listeners on dry land than at sea! The Shipping Forecast is issued by the UK Met Office and broadcast on BBC Radio 4 around daybreak, and after midnight …

IX. AGU News


WASHINGTON, DC – The Resilience Dialogues, a public-private collaborative effort to help local communities address climate-related vulnerabilities, today announced 10 communities will participate in the collaboration’s beta phase. Through the Resilience Dialogues, the communities will explore their risks from climate variability and change and work through a series of facilitated online dialogues with subject matter experts and scientists to learn how to reduce these risks and build community resilience. The first dialogues are expected to take place later this winter.