I. Science Policy
1. With 2017 Budget Signed into Law, Eyes Turn to 2018 Battle
Analysts hope that Congress will continue to support science programs in next year’s budget as well.
2. Defining Opportunities for Collaboration Across Data Life Cycles
Developing Enterprise Tools and Capacities for Large-Scale Natural Resource Monitoring; Fort Collins, Colorado, 12–13 October 2016
3. Newly Signed Federal Budget Is Favorable to Science
Budget bill signed by Trump this afternoon shows bipartisan congressional support for Earth and space sciences despite the administration’s initial goal of cutting nondefense discretionary spending.
II. Geochemistry, Mineralogy, Volcanology
1. Competing Models of Mountain Formation Reconciled
The author of a prize-winning paper published inGeochemistry, Geophysics, Geosystems describes new insights into crustal mechanics and the formation of the Himalaya.
2. Reinterpreting the Age and Origins of Taiwan’s Yuli Belt Terrane
Uranium-lead dating of zircons from Taiwan’s east central metamorphic belt offers robust evidence that this uplifted terrane is some 90 million years younger than previously thought.
III. Hazards & Disasters
1. Plague Bug May Have Lurked in Medieval England Between Outbreaks
A new analysis of climate records in England and Europe’s Low Countries suggests that the disease-causing bacterium persisted in rodents between recurrences in people.
2. Ancient Methane Seeps Tell Tale of Sudden Warming
Newly discovered rock mounds left by ancient methane seeps give scientists clues that methane on ancient ocean floor was released by ancient global warming.
3. Catching Glimpses of Centuries-Old Earthquakes
Researchers in the western United States survey the earthquakes that have torn up California for the past millennium.
IV. Climate Change
1. When Ocean and Atmosphere Couple, the Climate Wobbles
Every 25–30 years, the ocean and atmosphere conspire to produce an enhanced North Atlantic Oscillation
2. Reconstructing Past Sea Level Change to Understand the Future
PALSEA2 2016 Workshop: Sea-Level Budgets at Decadal to Millennial Time Scales to Bridge the Paleo and Instrumental Records; Mount Hood, Oregon, 19–21 September 2016
V. Mathematical Geophysics
1. Whither Heterogeneity and Stochastic Subsurface Hydrology?
A debate series in Water Resources Research examines the gap between research and practice in the application of stochastic concepts for describing subsurface heterogeneity.
VI. Geophysical Research Letters
1. Drivers of Arctic Ocean warming in CMIP5 models
We investigate changes in the Arctic Ocean energy budget simulated by 26 general circulation models from the Coupled Model Intercomparison Project Phase 5 framework. Our goal is to understand whether the Arctic Ocean warming between 1961 and 2099 is primarily driven by changes in the net atmospheric surface flux or by changes in the meridional oceanic heat flux. We find that the simulated Arctic Ocean warming is driven by positive anomalies in the net atmospheric surface flux in 11 models, by positive anomalies in the meridional oceanic heat flux in 11 models, and by positive anomalies in both energy fluxes in four models. The different behaviors are mainly characterized by the different changes in meridional oceanic heat flux that lead to different changes in the turbulent heat loss to the atmosphere. The multimodel ensemble mean is hence not representative of a consensus across the models in Arctic climate projections.
2. Tropical ocean-atmospheric forcing of Late Glacial and Holocene glacier fluctuations in the Cordillera Blanca, Peru
Evaluating the timing and style of past glacier fluctuations in the tropical Andes is important for our scientific understanding of global environmental change. Terrestrial cosmogenic nuclide ages on moraine boulders combined with 14C-dated clastic sediment records from alpine lakes document glacial variability in the Cordillera Blanca of Peru during the last ~16 ka. Late Glacial ice extents culminated at the start of the Antarctic Cold Reversal and began retracting prior to the Younger Dryas. Multiple moraine crests dating to the early Holocene mark brief readvances or stillstands that punctuated overall retreat of the Queshque Valley glacier terminus during this interval. Glaciers were less extensive during the middle Holocene before readvancing during the latest Holocene. These records suggest that tropical Atlantic and Pacific ocean-atmospheric processes exerted temporally variable forcing of Late Glacial and Holocene glacial changes in the Peruvian Andes.
3. Role of internal variability in recent decadal to multidecadal tropical Pacific climate changes
While the Earth's surface has considerably warmed over the past two decades, the tropical Pacific has featured a cooling of sea surface temperatures in its eastern and central parts, which went along with an unprecedented strengthening of the equatorial trade winds, the surface component of the Pacific Walker Circulation (PWC). Previous studies show that this decadal trend in the trade winds is generally beyond the range of decadal trends simulated by climate models when forced by historical radiative forcing.
4.Trajectories toward the 1.5°C Paris target: Modulation by the Interdecadal Pacific Oscillation
Global temperature is rapidly approaching the 1.5°C Paris target. In the absence of external cooling influences, such as volcanic eruptions, temperature projections are centered on a breaching of the 1.5°C target, relative to 1850–1900, before 2029. The phase of the Interdecadal Pacific Oscillation (IPO) will regulate the rate at which mean temperature approaches the 1.5°C level. A transition to the positive phase of the IPO would lead to a projected exceedance of the target centered around 2026. If the Pacific Ocean remains in its negative decadal phase, the target will be reached around 5 years later, in 2031. Given the temporary slowdown in global warming between 2000 and 2014, and recent initialized decadal predictions suggestive of a turnaround in the IPO, a sustained period of rapid temperature rise might be underway. In that case, the world will reach the 1.5°C level of warming several years sooner than if the negative IPO phase persists.
5. Fracture propagation and stability of ice shelves governed by ice shelf heterogeneity
Tabular iceberg calving and ice shelf retreat occurs after full-thickness fractures, known as rifts, propagate across an ice shelf. A quickly evolving rift signals a threat to the stability of Larsen C, the Antarctic Peninsula's largest ice shelf. Here we reveal the influence of ice shelf heterogeneity on the growth of this rift, with implications that challenge existing notions of ice shelf stability. Most of the rift extension has occurred in bursts after overcoming the resistance of suture zones that bind together neighboring glacier inflows. We model the stresses in the ice shelf to determine potential rift trajectories. Calving perturbations to ice flow will likely reach the grounding line. The stability of Larsen C may hinge on a single suture zone that stabilizes numerous upstream rifts. Elevated fracture toughness of suture zones may be the most important property that allows ice shelves to modulate Antarctica's contribution to sea level rise.
6. Persistent or repeated surface habitability on Mars during the late Hesperian - Amazonian
Large alluvial fan deposits on Mars record relatively recent habitable surface conditions (≲3.5 Ga, Late Hesperian - Amazonian). We find net sedimentation rate <(4–8) μm/yr in the alluvial fan deposits, using the frequency of craters that are interbedded with alluvial fan deposits as a fluvial-process chronometer. Considering only the observed interbedded craters sets a lower bound of >20 Myr on the total time interval spanned by alluvial fan aggradation, >103-fold longer than previous lower limits. A more realistic approach that corrects for craters fully entombed in the fan deposits raises the lower bound to >(100–300) Myr. Several factors not included in our calculations would further increase the lower bound. The lower bound rules out fan formation by a brief climate anomaly. Therefore, during the Late Hesperian - Amazonian on Mars, persistent or repeated processes permitted habitable surface conditions.
VII. AGU Blogs
1. Bands of extra-tough ice slow down cracks in Antarctica’s Larsen C ice shelf
The stability of the Antarctic Peninsula’s largest ice shelf may depend upon stripes of extremely strong ice running down its spine, a new study finds.
2. Hawaiian mountains could lose snow cover by 2100
A new study, accepted for publication in Earth’s Future, a journal of the American Geophysical Union, indicate that Hawaii’s two volcano summits are typically snow-covered at least 20 days each winter, on average, but that the snow cover will nearly disappear by the end of the century.
3. This is Long, but it Explains a Lot.
A friend of mine told me about this essay, and while Foreign Affairs magazine is not on my usual reading list, I see why it has such a high reputation. Take the time to read this.
4. Using Basic Algebra To Develop An Extreme Temperature Index
This is a cross-post from my friend and fellow meteorologist Guy Walton. Guy is working on an extreme temperature index that will take into account not just the magnitude of the record but weight this by the length of the record. Breaking a record at a site with 50 years of data is not as important as doing the same in a place with 135 years of data. The next …