I. Science Policy & Funding
1. Strong NSF Funding Favored by House Spending Committee
Although the federal budget request lowers the agency’s funding by 11%, a House appropriations committee chair declared at a hearing his panel’s commitment to U.S. leadership in fundamental research.
2. USGS Funding Slashed 15% in Proposed Federal Budget
Requested fiscal year 2018 spending levels support energy and mineral resources programs but make deep cuts to climate programs and many other areas.
II. Ocean Sciences
1. Impacts of “Bomb” Cyclones Reach the Ocean Floor
Japanese researchers study explosive cyclones with models to simulate decades of ocean circulation data.
2. Ocean Currents Push Mainland Pollution to Remote Islands
Marine protected areas, set up to conserve marine ecosystems and species, accumulate pollutants swept in from mainland shores by ocean currents.
III. Hazards & Disasters
1. Can Volcanic Gas Levels Predict an Eruption?
Researchers test whether the changing composition of volcanic gas can signal a coming eruption in Chile’s Villarrica volcano.
2. The Challenges Posed by Induced Seismicity
A recent paper in Reviews of Geophysics examined the increasing incidence of seismic events caused by industrial activities.
IV. Hydrology, Cryosphere & Earth Surface
1. Tracing Water Through the Critical Zone
The authors of a recent paper in Reviews of Geophysicsdescribe how isotope hydrology offers new insights into interactions at the interface between soil, vegetation, and the atmosphere.
V. Planetary Sciences
1. Instrument Development Enables Planetary Exploration
Third International Workshop on Instrumentation for Planetary Missions; Pasadena, California, 24–27 October 2016
2. Meteorites Mix Moon’s Surface at Both Small and Large Scales
A three-dimensional model of material transport suggests that impact cratering can mix lunar soils across distances of more than 100 kilometers.
1. Removing Carbon from the Ground Up
Massive plantations for storing carbon and growing biofuel won’t achieve the Paris Agreement’s “2-degree guardrail,” but they could help.
VII. Geophysical Research Letters
1. Nonlinear response of iceberg side melting to ocean currents
Icebergs calving into Greenlandic Fjords frequently experience strongly sheared flows over their draft, but the impact of this flow past the iceberg is not fully captured by existing parameterizations. We present a series of novel laboratory experiments to determine the dependence of submarine melting along iceberg sides on a background flow. We show, for the first time, that two distinct regimes of melting exist depending on the flow magnitude and consequent behavior of melt plumes (side-attached or side-detached), with correspondingly different meltwater spreading characteristics. When this velocity dependence is included in melt parameterizations, melt rates estimated for observed icebergs in the attached regime increase, consistent with observed iceberg submarine melt rates. We show that both attached and detached plume regimes are relevant to icebergs observed in a Greenland fjord. Further, depending on the regime, iceberg meltwater may either be confined to a surface layer or distributed over the iceberg draft.
2. An analytical model of maximum potential intensity for tropical cyclones incorporating the effect of ocean mixing
An analytical model of maximum potential intensity (PI) for tropical cyclones (TCs) incorporating wind-induced ocean cooling is developed on the basis of Emanuel's PI theory. The model consists of a one-dimensional ocean and an axisymmetric TC vortex that is translating at a constant speed. The model advances upon previous approaches by accounting for TC size and shape. The PI is determined at the radius of maximum winds by radially integrating the effect of ocean mixing using a specified wind profile. The resulting analytic ocean cooling agrees well with numerical solutions, and the new PI model better captures maximum intensities of observed TCs compared with Emanuel's original PI. It is also shown that the degree of cooling (i.e., ocean's feedback to atmosphere) can be quantified by a dimensionless parameter, representing the ratio of atmospheric forcing to ocean stability.
3. A new heat flux model for the Antarctic Peninsula incorporating spatially variable upper crustal radiogenic heat production
A new method for modeling heat flux shows that the upper crust contributes up to 70% of the Antarctic Peninsula's subglacial heat flux and that heat flux values are more variable at smaller spatial resolutions than geophysical methods can resolve. Results indicate a higher heat flux on the east and south of the Peninsula (mean 81 mW m−2) where silicic rocks predominate, than on the west and north (mean 67 mW m−2) where volcanic arc and quartzose sediments are dominant. While the data supports the contribution of heat-producing element-enriched granitic rocks to high heat flux values, sedimentary rocks can be of comparative importance dependent on their provenance and petrography. Models of subglacial heat flux must utilize a heterogeneous upper crust with variable radioactive heat production if they are to accurately predict basal conditions of the ice sheet. Our new methodology and data set facilitate improved numerical model simulations of ice sheet dynamics.
4. Variability and trends in surface seawater pCO2 and CO2 flux in the Pacific Ocean
Variability and change in the ocean sink of anthropogenic carbon dioxide (CO2) have implications for future climate and ocean acidification. Measurements of surface seawater CO2 partial pressure (pCO2) and wind speed from moored platforms are used to calculate high-resolution CO2 flux time series. Here we use the moored CO2fluxes to examine variability and its drivers over a range of time scales at four locations in the Pacific Ocean. There are significant surface seawater pCO2, salinity, and wind speed trends in the North Pacific subtropical gyre, especially during winter and spring, which reduce CO2 uptake over the 10 year record of this study. Starting in late 2013, elevated seawater pCO2 values driven by warm anomalies cause this region to be a net annual CO2 source for the first time in the observational record, demonstrating how climate forcing can influence the timing of an ocean region shift from CO2 sink to source.
5. The coastal mean dynamic topography in Norway observed by CryoSat-2 and GOCE
New-generation synthetic aperture radar altimetry, as implemented on CryoSat-2, observes sea surface heights in coastal areas that were previously not monitored by conventional altimetry. Therefore, CryoSat-2 is expected to improve the coastal mean dynamic topography (MDT). However, the MDT remains highly reliant on the geoid. Using new regional geoid models as well as CryoSat-2 data, we determine three geodetic coastal MDT models in Norway and validate them against independent tide-gauge observations and the operational coastal ocean model NorKyst800. The CryoSat-2 MDTs agree on the ～3–5 cm level with both tide-gauge geodetic and ocean MDTs along the Norwegian coast. In addition, we compute geostrophic surface currents to help identifying errors in the geoid models. We find that even though the regional geoid models are all based on the latest satellite gravity data as provided by GOCE, the resulting circulation patterns differ.
6. Intense deformation field at oceanic front inferred from directional sea surface roughness observations
Fine-scale current gradients at the ocean surface can be observed by sea surface roughness. More specifically, directional surface roughness anomalies are related to the different horizontal current gradient components. This paper reports results from a dedicated experiment during the Lagrangian Submesoscale Experiment (LASER) drifter deployment. A very sharp front, 50 m wide, is detected simultaneously in drifter trajectories, sea surface temperature, and sea surface roughness. A new observational method is applied, using Sun glitter reflections during multiple airplane passes to reconstruct the multiangle roughness anomaly. This multiangle anomaly is consistent with wave-current interactions over a front, including both cross-front convergence and along-front shear with cyclonic vorticity. Qualitatively, results agree with drifters and X-band radar observations. Quantitatively, the sharpness of roughness anomaly suggests intense current gradients, 0.3 m s−1 over the 50 m wide front. This work opens new perspectives for monitoring intense oceanic fronts using drones or satellite constellations.
7. A global probabilistic study of the ocean heat content low-frequency variability: Atmospheric forcing versus oceanic chaos
A global 1/4° ocean/sea ice 50-member ensemble simulation is used to disentangle the low-frequency imprints of the atmospherically forced oceanic variability and of the chaotic intrinsic oceanic variability (IOV) on the large-scale (10° × 10°) ocean heat content (OHC) between 1980 and 2010. The IOV explains most of the interannual-to-decadal large-scale OHC variance over substantial fractions of the global ocean area that increase with depth: 9%, 22%, and 31% in the 0–700 m, 700–2000 m and 2000 m bottom layers, respectively. Such areas concern principally eddy-active regions, mostly found in the Southern Ocean and in western boundary current extensions, and also concern the subtropical gyres at intermediate and deep levels. The oceanic chaos may also induce random multidecadal fluctuations so that large-scale regional OHC trends computed on the 1980–2010 period cannot be unambiguously attributed to the atmospheric forcing in several oceanic basins at various depths. These results are likely to raise detection and attribution issues from real observations.
VIII. AGU Blogs
1. New study evaluates efficiency of oceans as heat sink, atmospheric gases sponge (plus video)
A new study is one the first to estimate how much and how quickly the ocean absorbs atmospheric gases and contrast it with the efficiency of heat absorption. Using two computer models that simulate the ocean, scientists found that gases are more easily absorbed over time than heat energy.
2. Some clouds filled with ice lollipops
A cloud full of lollipops may sound like the most delicious carnival treat ever… except this cloud’s lollipops are made of ice. Scientists spotted the lollipop-shaped ice crystals during a research flight in southwest England. The researchers flew through a large cloud system in 2009 to better understand how ice forms at relatively mild temperatures.
3. Offshore wind turbines vulnerable to Category 5 hurricane gusts
Offshore wind turbines built according to current standards may not be able to withstand the powerful gusts of a Category 5 hurricane, creating potential risk for any such turbines built in hurricane-prone areas, new University of Colorado Boulder-led research shows. The study, which was conducted in collaboration with the National Center for Atmospheric Research in Boulder, Colorado and the U.S. Department of Energy’s National Renewable Energy Laboratory in Golden, Colorado, highlights the limitations of current turbine design and could provide guidance for manufacturers and engineers looking to build more hurricane-resilient turbines in the future.