I. Science Policy
1. Concern About Climate Change Drives Arctic Council Meeting
Actions taken by ministers at the meeting included an agreement on international Arctic scientific cooperation and adoption of recommendations of a report on the region’s changing state.
2. NOAA Officials Stress Hurricane Danger and Storm Safety
Agency scientists on a Hurricane Awareness Tour showcase NOAA research capabilities and warn that although winds can cause severe damage, the biggest killers are storm surges and inland flooding.
II. Geochemistry, Mineralogy, Volcanology
1. Unraveling the History of the India-Asia Collision
A study of deformed and metamorphosed rocks exposed in Tibet’s Lopu Range suggests that episodes of crustal shortening and extension during the evolution of the Himalaya are related to subduction processes.
III. Hazards & Disasters
1. Faulty Assumptions Impair Earthquake Hazard Assessment in Italy
Along faults in the Central Apennine Mountains, weather and landslides may cause rock exposure that is mistakenly attributed to earthquakes.
IV. Climate Change
1. Shifting Winds Write Their History on a New Zealand Lake Bed
A team of scientists finds a year-by-year record of climate history spanning the past 17,000 years at the bottom of a South Island lake.
2. In Patagonian Lakes, Glacial Meltwater Lies Low
A new study reveals key differences in ice-water interactions between glaciers that flow into lakes and glaciers that end in the sea.
3. Advancing a Multisphere Approach to Third Pole Research
The International Workshop on Land Surface Multi-spheres Processes of Tibetan Plateau; Xining, Qinghai Province, China, 8–10 August 2016
4. Climate Change Could Increase Allergy-Related Asthma ER Visits
If greenhouse gas emissions continue to increase through the end of this century, ER visits for allergic asthma could increase by 10 percent in the Midwest, Southeast, and Northeast combined.
V. Ocean Sciences
1. Autonomous Floats Shed New Light on the Ocean’s Many Hues
Argo float data reveal regional deviations from existing models of the relationship between ocean color and biogeochemistry.
VI. Space & Planets
1. Insights into the Habitability of Mars
NASA’s Curiosity rover explored the Kimberley region of Mars to search for signs that the planet was once habitable.
2. A New Theory May Explain “Impossible” TRAPPIST-1 Planets
The proposed formation scenario relies on unconventional processes to account for a bevy of seven Earth-sized exoplanets recently found orbiting an unlikely star.
3. New Explanation for “Meandering” Electrons Orbiting Earth
A new study proposes a simpler theory to explain a class of electrons zipping around Earth, propelled by magnetic explosions.
VII. Geophysical Research Letters
1. Fragmentation of wind-blown snow crystals
Understanding the dynamics driving the transformation of snowfall crystals into blowing snow particles is critical to correctly account for the energy and mass balances in polar and alpine regions. Here we propose a fragmentation theory of fractal snow crystals that explicitly links the size distribution of blowing snow particles to that of falling snow crystals. We use discrete element modeling of the fragmentation process to support the assumptions made in our theory. By combining this fragmentation model with a statistical mechanics model of blowing snow, we are able to reproduce the characteristic features of blowing snow size distributions measured in the field and in a wind tunnel. In particular, both model and measurements show the emergence of a self-similar scaling for large particle sizes and a systematic deviation from this scaling for small particle sizes.
2. Validation of the Soil Moisture Active Passive (SMAP) satellite soil moisture retrieval in an Arctic tundra environment
This study examines the Soil Moisture Active Passive soil moisture product on the Equal Area Scalable Earth-2 (EASE-2) 36 km Global cylindrical and North Polar azimuthal grids relative to two in situ soil moisture monitoring networks that were installed in 2015 and 2016. Results indicate that there is no relationship between the Soil Moisture Active Passive (SMAP) Level-2 passive soil moisture product and the upscaled in situ measurements. Additionally, there is very low correlation between modeled brightness temperature using the Community Microwave Emission Model and the Level-1 C SMAP brightness temperature interpolated to the EASE-2 Global grid; however, there is a much stronger relationship to the brightness temperature measurements interpolated to the North Polar grid, suggesting that the soil moisture product could be improved with interpolation on the North Polar grid.
3. Emergent archetype patterns of coupled hydrologic and biogeochemical responses in catchments
Relationships between in-stream dissolved solute concentrations (C) and discharge (Q) are useful indicators of catchment-scale processes. We combine a synthesis of observational records with a parsimonious stochastic modeling approach to test how C-Q relationships arise from spatial heterogeneity in catchment solute sources coupled with different timescales of reactions. Our model indicates that the dominant driver of emergent archetypical dilution, enrichment, and constant C-Qpatterns was structured heterogeneity of solute sources implemented as correlation of source concentration to travel time. Regardless of the C-Q pattern, with weak correlation between solute-source concentration and travel time, we consistently find lower variability in C than in Q, such that the predominant solute export regime is chemostatic. Consequently, the variance in exported loads is determined primarily by variance of Q. Efforts to improve stream water quality and ecological integrity in intensely managed catchments should lead away from landscape homogenization by introducing structured source heterogeneity.
4. Global distribution of groundwater-vegetation spatial covariation
Groundwater is an integral component of the water cycle, and it also influences the carbon cycle by supplying moisture to ecosystems. However, the extent and determinants of groundwater-vegetation interactions are poorly understood at the global scale. Using several high-resolution data products, we show that the spatial patterns of ecosystem gross primary productivity and groundwater table depth are correlated during at least one season in more than two thirds of the global vegetated area. Positive relationships, i.e., larger productivity under shallower groundwater table, predominate in moisture-limited dry to mesic conditions with herbaceous and shrub vegetation. Negative relationships, i.e., larger productivity under deeper groundwater, predominate in humid climates with forests, possibly indicating a drawdown of groundwater table due to substantial ecosystem water use. Interestingly, these opposite groundwater-vegetation interactions are primarily associated with differences in vegetation than with climate and surface characteristics. These findings put forth the first evidence, and a need for better representation, of extensive and non-negligible groundwater-vegetation interactions at the global scale.
5. Rough versus smooth topography along oceanic hotspot tracks: Observations and scaling analysis
Some hotspot tracks are topographically smooth and broad (Nazca, Carnegie/Cocos/Galápagos, Walvis, Iceland), while others are rough and discontinuous (Easter/Sala y Gomez, Tristan-Gough, Louisville, St. Helena, Hawaiian-Emperor). Smooth topography occurs when the lithospheric age at emplacement is young, favoring intrusive magmatism, whereas rough topography is due to isolated volcanic edifices constructed on older/thicker lithosphere. The main controls on the balance of intrusive versus extrusive magmatism are expected to be the hotspot swell volume flux Qs, plate hotspot relative speed v, and lithospheric elastic thickness Te, which can be combined as a dimensionless parameter R = (Qs/v)1/2/Te, which represents the ratio of plume heat to the lithospheric heat capacity. Observational constraints show that, except for the Ninetyeast Ridge, R is a good predictor of topographic character: for R < 1.5 hotspot tracks are topographically rough and dominated by volcanic edifices, whereas for R > 3 they are smooth and dominated by intrusion.
6. The regional influence of the Arctic Oscillation and Arctic Dipole on the wintertime Arctic surface radiation budget and sea ice growth
Large alluvial fan deposits on Mars record relatively recent habitable surface conditions (≲3.5 Ga, Late An analysis of 2000–2015 monthly Clouds and the Earth's Radiant Energy System-Energy Balanced and Filled (CERES-EBAF) and Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA2) data reveals statistically significant fall and wintertime relationships between Arctic surface longwave (LW) radiative flux anomalies and the Arctic Oscillation (AO) and Arctic Dipole (AD). Signifying a substantial regional imprint, a negative AD index corresponds with positive downwelling clear-sky LW flux anomalies (>10 W m−2) north of western Eurasia (0°E–120°E) and reduced sea ice growth in the Barents and Kara Seas in November–February. Conversely, a positive AO index coincides with negative clear-sky LW flux anomalies and minimal sea ice growth change in October–November across the Arctic. Increased (decreased) atmospheric temperature and water vapor coincide with the largest positive (negative) clear-sky flux anomalies. Positive surface LW cloud radiative effect anomalies also accompany the negative AD index in December–February. The results highlight a potential pathway by which Arctic atmospheric variability influences the regional surface radiation budget over areas of Arctic sea ice growth.
VIII. AGU Blogs
1. Warmer temps cause decline in key runoff measure
Since the mid-1980s, the percentage of precipitation that becomes streamflow in the Upper Rio Grande watershed has fallen more steeply than at any point in at least 445 years, according to a new study. While this decline was driven in part by the transition from an unusually wet period to an unusually dry period, rising temperatures deepened the trend.
2. Our Past Climate Is A Warning For the Future
There are some excellent books for non-scientists about our climate, but some of the best are written by Brian Fagan- an Archaeologist! His book The Long Summer is superb, and I am currently listening to a series of lectures he made for The Great Courses. Any story of human history is incomplete without looking at the role of climate, and in The Long Summer, Fagan points out that all of written …
3. Groundwater Speed Dating! Can you find a match?
Welcome to the first edition of groundwater speed dating. In today’s post I introduce you to a motley crew of isotopes and chemicals that hydrogeologists and geochemists use to date the age of groundwater.
4. Monday Geology Picture: Pahoehoe Lava Flow
For this week’s “Monday Geology Picture” here’s a stunning example of a pahoehoe lava flow. I took this picture back in March when I visited Piton de la Fournaise volcano on Réunion Island. I’ll be sharing more pictures from Réunion soon – stay tuned!