I. Climate Change

1. Reckoning with Climate’s Most Challenging Questions

Climate researchers outline a vision for the future of climate observations.

https://eos.org/research-spotlights/reckoning-with-climates-most-challenging-questions

2. Assessing the Many Influences of High-Latitude Dust

First International Conference on High Latitude Cold Climate Dust (HLCCD); Reykjavík, Iceland, 22–25 May 2017

https://eos.org/meeting-reports/assessing-the-many-influences-of-high-latitude-dust

3. Global Average Temperatures in 2017 Continued Upward Trend

Even when the warming from El Niño is removed, 2017 ranks among the hottest years on record.

https://eos.org/articles/global-average-temperatures-in-2017-continued-upward-trend

4. Climate Change Is National Security Risk, Congress Members Warn

The Trump administration’s recently released National Security Strategy differs sharply from Obama’s strategy, which identified climate change as a top strategic risk to the country.

https://eos.org/articles/climate-change-is-national-security-risk-congress-members-warn

II. Hazards & Disasters

1. Modeling Megathrust Zones

A recent paper in Review of Geophysics built a unifying model to predict the surface characteristics of large earthquakes.

https://eos.org/editors-vox/modeling-megathrust-zones

2. Airborne Fireball

A surprise sighting of a meteor in the sky above southeast Michigan.

https://eos.org/editors-vox/airborne-fireball

III. Science Policy

1. Prestigious Climate-Related Fellowships Rescinded

Reduced program is one of several that usually support climate science postdoctoral research but have eliminated or suspended funding opportunities.

https://eos.org/articles/prestigious-climate-related-fellowships-rescinded

IV. Biogeosciences

1. The Amazon River’s Ecosystem: Where Land Meets the Sea

What happens to plant matter on its journey down the Amazon River to the Atlantic Ocean? One research group investigated the region where river and ocean meet to fill in this part of the story.

https://eos.org/project-updates/the-amazon-rivers-ecosystem-where-land-meets-the-sea

V. Geology & Geophysics

1. Scientists Create Catalog of Altotiberina Fault in Italy

More than 37,000 small earthquakes paint a picture of the fault’s behavior and seismic potential.

https://eos.org/research-spotlights/scientists-create-catalog-of-altotiberina-fault-in-italy

2. Revised AGU Position Statement Addresses Climate Intervention

The American Geophysical Union urges further research and policy development with regard to climate intervention (previously called geoengineering) that considers impacts on society.

https://eos.org/agu-news/revised-agu-position-statement-addresses

VI. Geophysical Research Letters

1. Variation in Rising Limb of Colorado River Snowmelt Runoff Hydrograph Controlled by Dust Radiative Forcing in Snow

Common practice and conventional wisdom hold that fluctuations in air temperature control interannual variability in snowmelt and subsequent river runoff. However, recent observations in the Upper Colorado River Basin confirm that net solar radiation and by extension radiative forcing by dust deposited on snow cover exerts the primary forcing on snowmelt. We show that the variation in the shape of the rising limb of the annual hydrograph is controlled by variability in dust radiative forcing and surprisingly is independent of variations in winter and spring air temperatures. These observations suggest that hydroclimatic modeling must be improved to account for aerosol forcings of the water cycle. Anthropogenic climate change will likely reduce total snow accumulations and cause snowmelt runoff to occur earlier. However, dust radiative forcing of snowmelt is likely consuming important adaptive capacity that would allow human and natural systems to be more resilient to changing hydroclimatic conditions.

http://onlinelibrary.wiley.com/doi/10.1002/2017GL075826/full

2. Simultaneous Observations of Lower Band Chorus Emissions at the Equator and Microburst Precipitating Electrons in the Ionosphere

On 11 December 2016 at 00:12:30 UT, Van Allen Probe-B, at the equator and near midnight, and AC6-B, in the ionosphere, were on magnetic field lines whose 100 km altitude foot points were separated by 600 km. Van Allen Probe-B observed a 30 s burst of lower band chorus waves (with maximum amplitudes >1 nT) at the same time that AC6-B observed intense microburst electrons in the loss cone. One second averaged variations of the chorus intensity and the microburst electron flux were well correlated. The low-altitude electron flux expected from quasi-linear diffusion of the equatorial electrons by the equatorial chorus is in excellent agreement with the observed, 1 s averaged, low-altitude electron flux. However, the large-amplitude, <0.5 s duration, low-altitude electron pulses require nonlinear processes for their explanation.

http://onlinelibrary.wiley.com/doi/10.1002/2017GL076120/full

3. Regime-Dependent Differences in Surface Freshwater Exchange Estimates Over the Ocean

Differences in gridded precipitation (P), surface evaporation (E), and the resultant surface freshwater exchange (P − E) among different products over the ocean are diagnosed as functions of moisture advection (Qadvt) and moisture tendency by dynamical convergence (Qcnvg). Compared to the GPCP product, the TRMM3B42 product captures higher frequency of precipitation with larger extreme precipitation rates in regimes of deep convection and more light rain detections in regimes of frequent occurrence of boundary layer clouds. Discrepancies in E depend on moisture flux divergence, with the OAFlux product having the largest E in regimes of divergence. Discrepancies in mean P − E in deep convective regimes are highly influenced by differences in precipitation, with the TRMM3B42 product yielding P − Ehistograms closer to those inferred from the reanalysis moisture flux convergence. In nonconvergent regimes, observation-based P − E histograms skew toward positive values while the inferred reanalysis histograms are symmetric about the means.

http://onlinelibrary.wiley.com/doi/10.1002/2017GL075567/full

4. Circum-Antarctic Shoreward Heat Transport Derived From an Eddy- and Tide-Resolving Simulation

Almost all heat reaching the bases of Antarctica's ice shelves originates from warm Circumpolar Deep Water in the open Southern Ocean. This study quantifies the roles of mean and transient flows in transporting heat across almost the entire Antarctic continental slope and shelf using an ocean/sea ice model run at eddy- and tide-resolving (1/48°) horizontal resolution. Heat transfer by transient flows is approximately attributed to eddies and tides via a decomposition into time scales shorter than and longer than 1 day, respectively. It is shown that eddies transfer heat across the continental slope (ocean depths greater than 1,500 m), but tides produce a stronger shoreward heat flux across the shelf break (ocean depths between 500 m and 1,000 m).

http://onlinelibrary.wiley.com/doi/10.1002/2017GL075677/full

5. Arctic Sea Ice Loss in Different Regions Leads to Contrasting Northern Hemisphere Impacts

To explore the mechanisms linking Arctic sea ice loss to changes in midlatitude surface temperatures, we conduct idealized modeling experiments using an intermediate general circulation model and with sea ice loss confined to the Atlantic or Pacific sectors of the Arctic (Barents-Kara or Chukchi-Bering Seas). Extending previous findings, there are opposite effects on the winter stratospheric polar vortex for both large-magnitude (late 21st century) and moderate-magnitude sea ice loss. Accordingly, there are opposite tropospheric Arctic Oscillation (AO) responses for moderate-magnitude sea ice loss. However, there are similar strength negative AO responses for large-magnitude sea ice loss, suggesting that tropospheric mechanisms become relatively more important than stratospheric mechanisms as the sea ice loss magnitude increases. The midlatitude surface temperature response for each loss region and magnitude can be understood as the combination of an “indirect” part induced by the large-scale circulation (AO) response, and a residual “direct” part that is local to the loss region.

http://onlinelibrary.wiley.com/doi/10.1002/2017GL076433/full

6. Optimum Sea Surface Displacement and Fault Slip Distribution of the 2017 Tehuantepec Earthquake (Mw 8.2) in Mexico Estimated From Tsunami Waveforms

The 2017 Tehuantepec earthquake (Mw 8.2) was the first great normal fault event ever instrumentally recorded to occur in the Middle America Trench. The earthquake generated a tsunami with an amplitude of 1.8 m (height = 3.5 m) in Puerto Chiapas, Mexico. Tsunami waveforms recorded at coastal tide gauges and offshore buoy stations were used to estimate the optimum sea surface displacement without assuming any fault. Our optimum sea surface displacement model indicated that the maximum uplift of 0.5 m is located near the trench and the maximum subsidence of 0.8 m on the coastal side near the epicenter. We then estimated the fault slip distribution that can best explain the optimum sea surface displacement assuming 10 different fault geometries. The best model suggests that a compact region of large slip (3–6 m) extends from a depth of 30 km to 90 km, centered at a depth of 60 km.

http://onlinelibrary.wiley.com/doi/10.1002/2017GL076070/full

VII. AGU Blogs

1. American lobsters feeling the heat in the northwest Atlantic

Climate models project that ocean bottom temperatures in the Atlantic along the U.S. East Coast may rise by up to 4.3 degrees Celsius (7.7 degrees Fahrenehit) by the end of the century. The new study’s results show these rising temperatures will likely make conditions in the American lobster’s southernmost range—less hospitable in the future for juveniles, pushing them farther north and into habitats farther offshore.

https://blogs.agu.org/geospace/2018/01/22/american-lobsters-feeling-heat-northwest-atlantic/

2. 2017 Was Another Year of Amazing Heat. It’s not Natural, and It IS the Greenhouse Gases

NASA and NOAA both announced their global temperature results for 2017 today. NASA says it was the second warmest year on record and NOAA which does the analysis slightly differently came up with the 3rd hottest. Interestingly, if you remove the impacts of El Nino and La Nina, 2017 was THE hottest on record (see below).

https://blogs.agu.org/wildwildscience/2018/01/18/2017-another-year-amazing-heat-not-natural-greenhouse-gases/

3. Visitors to Our National Parks Deserve the Unvarnished Truth about History and Science

Note: The following is a guest post by Brian Ettling. It’s from his own blog, and I’m indebted to him for allowing me to share it here. I met Brian briefly at the AGU Science meeting in San Francisco a few years ago, and what he has to say is important.

https://blogs.agu.org/wildwildscience/2018/01/21/visitors-national-parks-deserve-unvarnished-truth-history-science/