I. Ocean Sciences

1. Challenges and Opportunities for Coastal Altimetry

10th Coastal Altimetry Workshop; Florence, Italy, 21–24 February 2017

https://eos.org/meeting-reports/challenges-and-opportunities-for-coastal-altimetry

2. Trump Administration Scrutinizing Protected Ocean Areas

A recently initiated review of some marine sanctuaries and monuments has conservationists worried that ecological, cultural, and other benefits from those protected areas may not be considered.

https://eos.org/articles/trump-administration-scrutinizing-protected-ocean-areas

II. Hazards & Disasters

1. Can Water Vapor Help Forecast When a Volcano Will Blow?

A widely used technique to monitor sulfur dioxide was tweaked to focus on water vapor at Peru’s Sabancaya Volcano. Results show that the volcano steamed up prior to its 2016 eruption.

https://eos.org/research-spotlights/can-water-vapor-help-forecast-when-a-volcano-will-blow

2. Probing the Power of Pacific Supertyphoons

Despite higher than normal surface temperatures and heat contents of ocean waters where the storms developed, evidence is lacking that global warming is revving them up.

https://eos.org/articles/probing-the-power-of-pacific-supertyphoons

3. How Storm Turbulence Can Spark Lightning

The turbulent pockets of air inside storms can help to build up static electricity in the atmosphere, according to a new study.

https://eos.org/research-spotlights/how-storm-turbulence-can-spark-lightning

III. Hydrology, Cryosphere & Earth Surface

1. Protecting Water Resources Through a Focus on Headwater Streams

Where Land Becomes Stream: Connecting Spatial and Temporal Scales to Better Understand and Manage Catchment Ecosystems; Rennes, France, 7–8 March 2017

https://eos.org/meeting-reports/protecting-water-resources-through-a-focus-on-headwater-streams

IV. Planetary Sciences

1. Where Are the Electrical Currents in the Enceladus Plume?

A plume of water ice that escapes Saturn’s moon Enceladus should be coursing with electrical currents, but data are mixed. Now simulations suggest that a sticky dust cloud may shield signals.

https://eos.org/research-spotlights/where-are-the-electrical-currents-in-the-enceladus-plume

V. Biogeosciences

1. Protecting Water Resources Through a Focus on Headwater Streams

Where Land Becomes Stream: Connecting Spatial and Temporal Scales to Better Understand and Manage Catchment Ecosystems; Rennes, France, 7–8 March 2017

https://eos.org/meeting-reports/protecting-water-resources-through-a-focus-on-headwater-streams

VI. Geophysical Research Letters

1. Unprecedented springtime retreat of Antarctic sea ice in 2016

During austral spring 2016 Antarctic sea ice extent (SIE) decreased at a record rate of 75 × 103 km2 d−1, which was 46% faster than the mean rate and 18% faster than in any previous spring season during the satellite era. The decrease of sea ice area was also exceptional and 28% greater than the mean. Anomalous negative retreat occurred in all sectors of the Antarctic but was greatest in the Weddell and Ross Seas. Record negative SIE anomalies for the day of year were recorded from 3 November 2016 to 9 April 2017. Rapid ice retreat in the Weddell Sea took place in strong northerly flow after an early maximum ice extent in late August. Rapid ice retreat occurred in November in the Ross Sea when surface pressure was at a record high level, with the Southern Annular Mode at its most negative for that month since 1968.

http://onlinelibrary.wiley.com/doi/10.1002/2017GL073656/full

2. Increasing frequency and duration of Arctic winter warming events

Near-surface air temperatures close to 0°C were observed in situ over sea ice in the central Arctic during the last three winter seasons. Here we use in situ winter (December–March) temperature observations, such as those from Soviet North Pole drifting stations and ocean buoys, to determine how common Arctic winter warming events are. Observations of winter warming events exist over most of the Arctic Basin. Temperatures exceeding −5°C were observed during >30% of winters from 1954 to 2010 by North Pole drifting stations or ocean buoys. Using the ERA-Interim record (1979–2016), we show that the North Pole (NP) region typically experiences 10 warming events (T2m > −10°C) per winter, compared with only five in the Pacific Central Arctic (PCA). There is a positive trend in the overall duration of winter warming events for both the NP region (4.25 days/decade) and PCA (1.16 days/decade), due to an increased number of events of longer duration.

http://onlinelibrary.wiley.com/doi/10.1002/2017GL073395/full

3. Niche construction by non-diazotrophs for N2 fixers in the eastern tropical North Atlantic Ocean

Diazotrophic dinitrogen (N2) fixation contributes ~76% to “new” nitrogen inputs to the sunlit open ocean, but environmental factors determining N2 fixation rates are not well constrained. Excess phosphate (phosphate–nitrate/16 > 0) and iron availability control N2 fixation rates in the eastern tropical North Atlantic (ETNA), but it remains an open question how excess phosphate is generated within or supplied to the phosphate-depleted sunlit layer. Our observations in the ETNA region (8°N–15°N, 19°W–23°W) suggest that Prochlorococcus and Synechococcus, the two ubiquitous non-diazotrophic cyanobacteria with cellular N:P ratios higher than the Redfield ratio, create an environment of excess phosphate, which cannot be explained by diapycnal mixing, atmospheric, and riverine inputs. Thus, our results unveil a new biogeochemical niche construction mechanism by non-diazotrophic cyanobacteria for their diazotrophic phylum group members (N2 fixers). Our observations may help to understand the prevalence of diazotrophy in low-phosphate, oligotrophic regions.

http://onlinelibrary.wiley.com/doi/10.1002/2017GL074218/full

4. The free troposphere as a potential source of arctic boundary layer aerosol particles

This study investigates aerosol particle transport from the free troposphere to the boundary layer in the summertime high Arctic. Observations from the Arctic Summer Cloud Ocean Study field campaign show several occurrences of high aerosol particle concentrations above the boundary layer top. Large-eddy simulations suggest that when these enhanced aerosol concentrations are present, they can be an important source of aerosol particles for the boundary layer. Most particles are transported to the boundary layer by entrainment. However, it is found that mixed-phase stratocumulus clouds, which often extend into the inversion layer, also can mediate the transport of particles into the boundary layer by activation at cloud top and evaporation below cloud base. Finally, the simulations also suggest that aerosol properties at the surface sometimes may not be good indicators of aerosol properties in the cloud layer.

http://onlinelibrary.wiley.com/doi/10.1002/2017GL073808/full

5. Tectonic tremor and LFEs on a reverse fault in Taiwan

We compare low-frequency earthquakes (LFEs) from triggered and ambient tremor under the southern Central Range, Taiwan. We apply the PageRank algorithm used by Aguiar and Beroza (2014) that exploits the repetitive nature of the LFEs to find repeating LFEs in both ambient and triggered tremor. We use these repeaters to create LFE templates and find that the templates created from both tremor types are very similar. To test their similarity, we use both interchangeably and find that most of both the ambient and triggered tremor match the LFE templates created from either data set, suggesting that LFEs for both events have a common origin. We locate the LFEs by using local earthquake P wave and S wave information and find that LFEs from triggered and ambient tremor locate to between 20 and 35 km on what we interpret as the deep extension of the Chaochou-Lishan Fault.

http://onlinelibrary.wiley.com/doi/10.1002/2016GL072148/full

6. The role of the Southern Hemisphere semiannual oscillation in the development of a precursor to central and eastern Pacific Southern Oscillation warm events

The semiannual oscillation (SAO) is a twice-yearly northward movement (in May-June-July (MJJ) and November-December-January (NDJ)) of the circumpolar trough of sea level pressure (SLP) in the Southern Hemisphere with effects throughout the troposphere. During MJJ the second harmonic of SLP, describing the SAO, has low values of SLP north of 50°S in the subtropical South Pacific, while the first harmonic, which is dominant over the Australian sector, increases to its peak. This once-a-year peak in negative SLP gradients (decreasing to the east) between Australia and the ocean to its east extends to the equatorial Pacific. Southern Oscillation warm events since 1950, with an intensification of this seasonal cycle, have larger-amplitude SST anomalies in the eastern equatorial Pacific in MJJ and during the following mature phase in NDJ. Weak amplification of the seasonal cycle in MJJ tends to be followed by larger-amplitude SST anomalies in the central equatorial Pacific during NDJ.

http://onlinelibrary.wiley.com/doi/10.1002/2017GL073832/full

VII. AGU Blogs

1. Greenland’s summer ocean bloom likely fueled by iron

Iron particles catching a ride on glacial meltwater washed out to sea by drifting currents is likely fueling a recently discovered summer algal bloom off the southern coast of Greenland, a new study finds. Microalgae, also known as phytoplankton, are plant-like, marine microorganisms that form the base of the food web in many parts of the ocean.

http://blogs.agu.org/geospace/2017/07/07/greenlands-summer-ocean-bloom-likely-fueled-iron/

2. NASA Satellite Sees Air Pollution from Fireworks on the 4th

Suffice to say, those with asthma and other breathing disorders might want to watch the fireworks on TV next year. I was surprised at how strong the signal was. The fact that independence was declared in early July when the atmosphere is fairly quiet with light winds, means the dispersal will be slow. Even more so when you have a low-level temperature inversion that can trap the fine particles near …

http://blogs.agu.org/wildwildscience/2017/07/07/nasa-satellite-sees-air-pollution-fireworks-4th/

3. GOES-16 View of the SAL around Tropical Depression 4.

The image above is from GOES-16 (Ctsy. CIRA) and you can easily see the dry dusty Saharan air to the North and east of Tropical Depression 4. This layer of dusty air is called the SAL for Saharan Air Layer, and it often inhibits tropical cyclones. It’s already impacting TD 4. The new GOES-16 continues to wow we meteorologists. Truly, a new era is underway.

http://blogs.agu.org/wildwildscience/2017/07/06/goes-16-view-sal-around-tropical-depression-4/

4. Yet Another Climate Myth Is Gone

Update July 5, 2017: Carl Mears (one of the authors of the paper) has written an excellent FAQ about this subject that is well worth looking at. The myth that the satellite temperature measurements do not match the surface temperature record is one of the most enduring climate myths, but it’s now in the dustbin of history.

http://blogs.agu.org/wildwildscience/2017/07/04/yet-another-climate-myth-gone/

VIII. AGU News

1. NEW SURVEY HIGHLIGHTS GENDER, RACIAL HARASSMENT IN ASTRONOMY AND PLANETARY SCIENCE

WASHINGTON, DC — Women of color working in astronomy and planetary science report more gender and racial harassment than any other gender or racial group in the field, according to a new study revealing widespread harassment in these scientific disciplines.https://news.agu.org/press-release/new-survey-highlights-gender-racial-harassment-in-astronomy-and-planetary-science/