I. Climate Change
1. The Stratosphere and Its Role in Tropical Teleconnections
Joint SPARC Dynamics and Observations Workshop; Kyoto, Japan, 9–14 October 2017
https://eos.org/meeting-reports/the-stratosphere-and-its-role-in-tropical-teleconnections
2. Challenges of Forecasting Flooding on Coral Reef–Lined Coasts
Understanding Flooding on Reef-lined Island Coasts Workshop; Honolulu, Hawaii, 5–7 February 2018
https://eos.org/meeting-reports/challenges-of-forecasting-flooding-on-coral-reef-lined-coasts
3. NOAA Seeks Emerging Technologies to Further Its Mission
National Oceanic and Atmospheric Administration Emerging Technologies for Observations Workshop; College Park, Maryland, 22–23 August 2017
https://eos.org/meeting-reports/noaa-seeks-emerging-technologies-to-further-its-mission
4. Record-breaking Ocean Heat Fueled Hurricane Harvey
Ocean evaporation matched up with massive overland rainfall, new analysis finds.
https://eos.org/scientific-press/record-breaking-ocean-heat-fueled-hurricane-harvey
II. Hazards & Disasters
1. Steam-Driven Blasts Last Seen at Kīlauea in 1924 May Recur
Sinking magma levels and rockfalls prompt warnings, flight restrictions, and the shutdown of Hawai’i Volcanoes National Park.
https://eos.org/articles/steam-driven-blasts-last-seen-at-kilauea-in-1924-may-recur
2. A Near-Real-Time Tool to Characterize Global Landslide Hazards
By fusing susceptibility information with precipitation data, a new model generates “nowcasts” to predict the potential for rainfall-triggered landslides in steep terrain between 50°N and 50°S.
https://eos.org/research-spotlights/a-near-real-time-tool-to-characterize-global-landslide-hazards
3. Hurricanes and the Sea: It Takes Two to Tango
A new special issue of JGR: Oceans reveals the rich relationship between the ocean and tropical cyclones.
https://eos.org/editors-vox/hurricanes-and-the-sea-it-takes-two-to-tango
III. Biogeosciences
1. Methane, Climate Change, and Our Uncertain Future
Methane is generally considered secondary to carbon dioxide in its importance to climate change, but what role might methane play in the future if global temperatures continue to rise?
https://eos.org/editors-vox/methane-climate-change-and-our-uncertain-future
IV. Ocean Sciences
1. Using Microbes to Predict the Flow of Arctic Rivers
Bacterial DNA provides a good estimate of river discharge.
https://eos.org/research-spotlights/using-microbes-to-predict-the-flow-of-arctic-rivers
2. Multiple Choices Exist for Changing Ocean Oxygen Concentrations
Widespread declines in ocean oxygen concentrations are now being reported with authors offering quite different explanations. Which ones are correct?
https://eos.org/editors-vox/multiple-choices-exist-for-changing-ocean-oxygen-concentrations
V. Geology & Geophysics
1. Tasty Treats from the 2018 Great Geobakeoff
Eat your way across fascinating geologic marvels, one sweet, sugary dessert at a time.
https://eos.org/geofizz/tasty-treats-from-the-2018-great-geobakeoff
VI. Planetary Sciences
1. How Did Venus Get its Youthful Surface?
Catastrophic lithospheric recycling is unlikely to be the cause of Venus’s young surface from mantle convection models constrained by offset between the center of mass and center of shape of planet.
https://eos.org/editor-highlights/how-did-venus-get-its-youthful-surface
2. Anatomy of a Flux Rope Hurtling Through the Solar System
Pancaking and erosion can explain a lot of the structural change in magnetic flux ropes as they fly evolve during their supersonic flight through the inner solar system.
https://eos.org/editor-highlights/anatomy-of-a-flux-rope-hurtling-through-the-solar-system
3. A Consistent Model of Ice Dissociation on Celestial Bodies
A model based on decades of experimental results can now quantify the products of water ice dissociation caused by radiation and predict the products expelled into an icy body’s outer atmosphere.
https://eos.org/research-spotlights/a-consistent-model-of-ice-dissociation-on-celestial-bodies
VII. Geophysical Research Letters
1. Numerical Studies of Submesoscale Island Wakes in the Kuroshio
Submesoscale wake formation at Green Island (∼7 km) in the Kuroshio is examined by the three‐dimensional numerical simulations, which are validated by field observations. On the basis of geophysical (rotating and stratified) flow, the wake exhibits sequentially detached recirculation, containing upwelling of cold water, propagates downstream via advection, forming an along stream oscillating wake, resembling to the von Kármán vortex streets (VKVS). Evidence includes (1) the shedding frequency as a function of the horizontal eddy viscosity shows a trend analogous with classical wakes; (2) The wake behaviors depend on the Reynolds number (Re), where the turbulent transition regime is determined; (3) The aspect ratio of the island wakes is similar to the ratio of the VKVS. Unlike classical wakes, the vortex street features are adapted by inertial and barotropic instabilities. The inertial instability has large growth rate and tends to slightly destabilize the anticyclonic recirculation. The barotropic instability could be a secondary process to generate eddy kinetic energy at downstream. Finally, our model suggests the hotspot of the turbulent mixing in the wake is located at the plane free shear layer as a result of the vertical shear instability, which is induced by the island‐shelf effect and the tilting of the vertical vorticity.
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2017JC013501
This paper presents an assessment and comparison of recent mean sea surface (MSS) models. Using a new approach and independent altimeter datasets, we quantify the major improvement of the CNES_CLS15 and the DTU15 models.
We observe a reduction in the amplitude of omission errors thanks to the use of new geodetic altimeter datasets (i.e. Cryosat‐2 and Jason‐1 geodetic): they are reduced by a factor of 2 compared with previous generations (CNES_CLS11).
We also quantify commission errors resulting from the leakage of residual ocean variability and altimeter noise into the MSS models. For wavelengths shorter than 250 km, the error is of the order of 1 to 2 cm2, i.e. ∼10 to 20% of the sea level anomaly (SLA) variance.
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2017JC013503
The regional variability and turbulent characteristics of submesoscale surface chlorophyll concentrations are examined with hourly maps of geostationary ocean color imagery‐derived chlorophyll concentrations at a 0.5‐km resolution for a period of five years (2011 to 2015) over the East/Japan Sea with concurrent mesoscale and submesoscale observations. Two seasonal blooms occur in the spring and fall within 250 km off the coast that are associated with constructive combinations of light exposure, nutrients, and vertical stratification. Another bloom occurs in the summer and is closely related to regional wind‐driven upwelling events. The spring and fall blooms are more significant near the coast (within 40 km from the coast) than offshore because of the more energetic submesoscale horizontal shear and vortical phenomena onshore as well as their propagation in the cross‐shore direction. In addition, the regional spring bloom starts offshore and migrate onshore with a time delay of one month, which may result from the onshore propagation of geostrophic currents, the deepening of the mixed layer, and favorable nutrient fluxes from the subsurface. The wavenumber‐domain energy spectra of chlorophyll concentrations exhibit anisotropy, which may be closely related to bathymetric effects and regional circulations. The spectral decay slopes change from k‐5/3 to k‐1 at the O(10) km scales and from k‐1 to k≤‐3 at the O(1) km scales and have weak seasonality. These results are consistent with the two‐dimensional quasi‐geostrophic turbulence theory and can be interpreted with the baroclinic instability energized from the moderate seasonal mixed layer under mesoscale regional circulations.
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2017JC013732
4. Numerical Modeling of the Interactions of Oil, Marine Snow, and Riverine Sediments in the Ocean
Natural or spilled oil in the ocean can interact with marine snow and sediment from riverine sources and form marine oil snow (MOS) aggregates including aggregates consisting of phytoplankton, detrius and feces. Such aggregates have a fractal structure and can transport oil from the surface layers to greater depths in the ocean, eventually settling on the seafloor. In recent studies of the Deepwater Horizon and IXTOC‐1 oil spills in the Gulf of Mexico, this process was identified as one of the main mechanisms for transporting oil vertically in the water column. We have adapted a stochastic, one‐dimensional numerical model that uses coagulation theory to simulate MOS formation and sinking in the ocean and predict the time evolution of physical properties and spatial distribution of MOS. Here we present the model development, calibration and validation with measured MOS field data in the Gulf of Mexico during the Deepwater Horizon spill. We use a sensitivity analysis to identify critical parameters, and suggest future model improvements and areas where further experimental investigation is needed to improve our understanding of MOS formation and sedimentaion. The model can be used during response and planning activities associated with oil spills in the marine environments.
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JC013790
5. Retrieval of Barometric Pressure from Satellite Passive Microwave Observations Over the Oceans
Sea surface barometric pressure is one of the few key geophysical variables has not been derived from satellite observations. In this study, we investigate the retrieval of sea surface barometric pressure from passive microwave observations. The direct relationship between surface barometric pressure and upward‐emitted brightness temperature observed by a microwave radiometer is deduced and validated. A statistical retrieval algorithm based on the back‐propagation (BP) neural networks is proposed to estimate sea surface barometric pressure using the observations from the Advanced Technology Microwave Sounder (ATMS) onboard the Suomi‐National Polar‐Orbiting Operational Environmental Satellite System Preparatory Project (SNPP) satellite. In situ buoy measurements and reanalysis data are used to assess the retrieval performance. Experimental results show that the proposed retrieval algorithm can estimate sea surface barometric pressure over mid‐to‐low latitude areas (40°S ‐ 40 °N) with the root mean square errors of less than 2.0 hPa, 3.0 hPa, and 3.5 hPa for clear‐sky, cloudy, and rainy conditions, respectively. Several tropical cyclone retrieval experiments also show that the proposed retrieval algorithm behaves well under high wind conditions (15 m/s<wind speed<28 m/s).
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JC013847
We examine the surface and subsurface signature of ocean fronts closely associated with the Malvinas Current dynamics. We first evaluate the performances of the Mercator‐ocean eddy permitting (1/12° spatial resolution) global operational system in the Southwestern Atlantic Ocean over the last 10 years (2007‐2016) using satellite, Argo float and in situ data collected near 41°S. Observations versus model comparisons show that the model correctly reproduces the general circulation and the complex hydrographic features of the study area including the vicinity of the Brazil‐Malvinas Confluence. The model outputs accurately match the observations except in June 2015. The causes for the June 2015 mismatch are analyzed. We then used the model and satellite altimetry to identify isolines of absolute dynamic topography (ADT) and potential density at different depths associated with the mean front location and establish their correspondence with specific water mass boundaries. Frontal displacements as depicted in satellite ADT, model ADT and model potential density at 450 m are in general agreement. The ADT and potential density at 450 m provide non‐identical and complementary information on eddies shed by the Polar Front (PF): while ADT depicts the surface circulation with PF eddies entrained into the energetic circulation over the deep Argentine Basin, potential density at 450 m is more effective at monitoring PF eddies feeding the Malvinas Current.
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JC013887
VII. AGU Blogs
1. Antarctic seals can help predict ice sheet melt
Two species of seal found in Antarctic seas are helping scientists collect data about the temperature and salinity of waters around vulnerable ice sheets in West Antarctica.
https://blogs.agu.org/geospace/2018/05/15/antarctic-seals-can-help-predict-ice-sheet-melt/
2. Sounds of melting glaciers could reveal how fast they shrink
Scientists could potentially use the racket made by melting glaciers to estimate how fast they are disappearing, according to new study of audio recordings captured in the waters of an Arctic fjord. New underwater recordings taken from Hornsund fjord in Svalbard, Norway, show melting icebergs make more noise the faster they melt. The recordings also distinguish melting sounds from grounded glaciers and floating icebergs.
https://blogs.agu.org/geospace/2018/05/10/sounds-of-melting-glaciers-could-reveal-how-fast-they-shrink/
3. Voyage to the White Shark Café: Micronekton–On the Dinner Menu
In all of the world’s oceans, billions of small animals commute between their daytime habitat – 200 to 1,000 meters deep- and their nighttime feeding grounds, just below the surface.
https://blogs.agu.org/thefield/2018/05/15/voyage-to-the-white-shark-cafe-micronekton-on-the-dinner-menu/
4. Popof Glacier Retreat, Alaska Features Tributary Separation
Popof Glacier comparison in 1986 and 2016 Landsat images. Red arrow is the 1986 terminus location, yellow arrows the 2016 terminus location, pink arrows indicate two key tributaries and purple dots indicate the snowline. Popof Glacier is at the southern end of the Stiking Icefield in southeast Alaska. In 1948 the glacier had two terminus sections that separated around Mount Basargin and then rejoined.
https://blogs.agu.org/fromaglaciersperspective/2018/05/15/popof-glacier-retreat-alaska-features-tributary-separation/
5. Ablation Variation with time Across Variable Glacier Surface
This post was prompted by comments from Ruth Mottram about funding for ablation process studies and the work by Fausto et al (2016) that noted non-radiative forces dominated the energy fluxes for ablation on the Greenland Ice Sheet during a period of high ablation in July 2012. This reminded me of a study we conducted some 25 years ago on the variation of ablation through time across a variable glacier …
https://blogs.agu.org/fromaglaciersperspective/2018/05/10/ablation-variation-with-time-across-variable-glacier-surface/
