I.Climate Change
1.Effects of Acid Rain, Climate Change on Freshwater Lakes
New England lakes weathered years of acid rain. A new study tracks how they are faring after 30 years of regulation and how climate change factors into the equation.
https://eos.org/research-spotlights/effects-of-acid-rain-climate-change-on-freshwater-lakes
2.Tiny Algae May Have Prompted a Mass Extinction
Dead algae sinking to the ocean floor may have sequestered carbon 445 million years ago, triggering the glaciation that accompanied the Late Ordovician mass extinction.
https://eos.org/articles/tiny-algae-may-have-prompted-a-mass-extinction
II.Science Policy & Funding
1.Environmentalists Are Glad Pruitt Is Out but Worry What’s Next
With Scott Pruitt’s resignation, EPA deputy administrator Andrew Wheeler, a former coal lobbyist, takes charge and is likely to continue the same deregulation and antienvironment policies.
https://eos.org/articles/environmentalists-are-glad-pruitt-is-out-but-worry-whats-next
III.Ocean Sciences
1.Exploring the Interplay Between Ocean Eddies and the Atmosphere
Ocean Mesoscale Eddy Interactions with the Atmosphere: A CLIVAR Workshop; Portland, Oregon, 17–18 February 2018
https://eos.org/meeting-reports/exploring-the-interplay-between-ocean-eddies-and-the-atmosphere
1.The Challenges of Global Flood Hazard Mapping and Prediction
A new book presents the latest tools in remote sensing technologies and modeling approaches for addressing challenges and meeting future needs in global flood hazard mapping and prediction.
https://eos.org/editors-vox/the-challenges-of-global-flood-hazard-mapping-and-prediction
V.Planetary Sciences
1.Tracing the Steps of Hydrothermal Activity in Hrad Vallis, Mars
Conditions that formed Amazonian age valleys may have been hospitable to microbial life.
https://eos.org/research-spotlights/tracing-the-steps-of-hydrothermal-activity-in-hrad-vallis-mars
VI.Education
1.Connecting Students and Mentors Through Local Research Hubs
An online database can help connect prospective student researchers with university faculty members and collaborative projects that need their help. Could this model work at your university?
https://eos.org/project-updates/connecting-students-and-mentors-through-local-research-hubs
VII.Geophysical Research Letters
1.Assessing the presenceof discontinuities in the ocean color satellite record and their effects on chlorophyll trends and their uncertainties
Ocean color sensors are crucial for understanding global phytoplankton dynamics. However, the limited life spans of sensors make multi‐sensor datasets necessary for estimating long‐term trends. Discontinuities may be introduced when merging data between sensors, potentially affecting trend estimates and their uncertainties. We use a Bayesian spatio‐temporal model to investigate the presence of discontinuities and their impacts on estimated chlorophyll trends. The discontinuities considered are the introduction of MERIS, MODIS‐Aqua, and VIIRS, and the termination of Sea WiFS. Discontinuities are detected in ~70 % of regions, affecting trend estimates (~60 % of regions have statistically different trends), and potentially even biasing trend estimates (opposite sign in ~13 % of regions). Considering a single discontinuity increases trend uncertainty by an average of 0.20%yr‐1 (0.59%yr‐1 for two discontinuities). This difference in trend magnitude and uncertainty highlights the importance of minimizing discontinuities in multi‐sensor records and taking into account discontinuities when analyzing trends.
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2017GL076928
2.Coastal Sulfur Plumes off Peru during El Niño, La Niña and Neutral Phases
For the first time, the impact of the El Niño‐Southern Oscillation (ENSO) on the surface sulfur plumes off the Peruvian upwelling system has been studied. The investigations demonstrated a strong correlation between the ENSO and the sulfur plumes in the coastal areas of Callao and Pisco. During the El Niño phases, the sulfur plumes disappeared almost completely because of equatorial remotely forced oxygenation episodes. The La Niña events were associated with strong oxygen deficiency over the Peruvian shelf, supporting the formation of hydrogen sulfide and, consequently, the occurrence of sulfur plumes. This impact was smaller at Callao, because the La Niña phases in this coastal area were interrupted by weak oxygenation events. During the neutral phases, oxygen‐poor waters were also present in the Peruvian shelf areas, promoting the large size of sulfur plumes. However, they were not forced by the remotely driven processes resulting from ENSO phenomena.
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL077618
3.Unraveling Phytoplankton Community Dynamics in the Northern Chukchi Sea under Sea‐Ice‐Covered and Sea‐Ice‐Free Conditions
The timing of sea ice retreat, light availability and sea surface stratification largely control the phytoplankton community composition in the Chukchi Sea. This region is experiencing a significant warming trend, an overall decrease in sea ice cover, and a documented decline in annual sea ice persistence and thickness over the past several decades. The consequences of earlier seasonal sea ice retreat and a longer sea‐ice‐free season on phytoplankton community composition warrants investigation. We applied multivariate statistical techniques to elucidate the mechanisms that relate environmental variables to phytoplankton community composition in the Chukchi Sea using data collected during a single field campaign in the summer of 2011. Three phytoplankton groups emerged that were correlated with sea ice, sea surface temperature (SST), nutrients, salinity and light. Longer ice‐free duration in a future Chukchi Sea will result in warmer SSTs and nutrient depletion, which we conclude will favor other phytoplankton types over larger diatoms.
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL077684
4.Ocean‐induced melt triggers glacier retreat in Northwest Greenland
In recent decades, tidewater glaciers in Northwest Greenland contributed significantly to sea level rise but exhibited a complex spatial pattern of retreat. Here, we use novel observations of bathymetry and water temperature from NASA's Ocean Melting Greenland mission to quantify the role of warm, salty Atlantic Water in controlling the evolution of 37 glaciers. Modeled ocean‐induced undercutting of calving margins compared with ice advection and ice‐front retreat observed by satellites from 1985 to 2015 indicate that 35 glaciers retreated when cumulative anomalies in ocean‐induced undercutting rose above the range of seasonal variability of calving‐front positions, while 2 glaciers standing on shallow sills and colder water did not retreat. Deviations in the observed timing of retreat are explained by residual uncertainties in bathymetry, inefficient mixing of waters in shallow fjords, and the presence of small floating sections. Overall, warmer ocean temperature triggered the retreat, but calving processes dominate ablation (71%).
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL078024
VIII.AGU Blogs
1. Glaciers Abandon Farragut River Valley, Alaska
The Farragut River drains into Frederick Sound in Southeast Alaska. The headwaters of this river in 1985 was a valley glacier, Farragut Glacier, fed by seven glaciers descending from peaks on the south wall of the valley or flowing down from the Stikine Icefield. The river is known for significant Pink and chinook salmon runs as well. This valley is just to the north of Baird Glacierthat has begun to retreat.
2. Mozigou Glacier Meltwater Pays High Hydropower Dividend
Mozigou Glacier is a valley glacier in the Gongga Mountains, Sichuan Province, China that drains into the Dadu River. In the first 250 km after leaving the glacier this meltwater travels through seven hydropower projects that have a collective capacity of over 9000 MW. Pan et al (2012) noted that the glaciers of the Gongga Shan have lost 11% of their area since 1966. They further reported a 300 m retreat of Mozigou Glacier from 1994-2009. The glacier unlike its neighbor Hailuoguo Glacier does not have a debris covered terminus. Liu et al (2010) report that the main change in the region affecting the glaciers is rising temperature. The Gongga Shan glaciers are summer accumulation type with the majority of the accumulating snow occurring at the same time that ablation is at a peak lower on the glacier. They also report a steep precipitation gradient, which is key to glacier formation here. Here we examine Landsat imagery from 1994-2017 to indicate retreat of the glacier and Google Earth images of the hydropower projects to underscore the economic output of the runoff.
https://blogs.agu.org/fromaglaciersperspective/2018/07/11/mozigou-glacier-meltwater-pays-high-hydropower-dividend/
