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AGU Research Spotlight (Jun 15-Jun 21, 2018)

2018-06-22 09:06:46

I. Climate Change

1.Rethinking the River

The Mississippi River and its delta and plume provide insights into research-informed approaches to managing river-dominated coastal zones.


2.Can We Crack the Climate Code of the Southern Polar Region?

Comprehensive Earth system models (ESMs) and climate models are the main tools available for quantitative projections of future climate change and likely physical outcomes. However, diagnosing Southern Hemisphere model performance is difficult because of the spatial sparseness of field data and remaining uncertainties in reconstructions of recent real-world climate conditions. These factors limit the evaluation of ESMs and thus the reliability of their projections, especially at high spatial resolution.


II.Hydrology, Cryosphere & Earth Surface

1.A Closer Look at Turbulent Transport in Gravel Streambeds

Lab-built streams reveal new insights into turbulence-driven exchange of dissolved substances between stream water and sediments below.


2.Rare Glacial River Drains Potentially Harmful Lakes

Antarctic lakes have contributed to ice shelf breakup in the past, but a glacier in Greenland appears safe from a similar fate, thanks to a river that drains away water.


III.Space Science & Space Physics

1.Going with the Flow in Outer Space

Near-Earth space is a dynamic electric environment containing different types of current that are continually changing over time and space.


IV.Planetary Sciences

1.Explosive Volcanoes Spawned Mysterious Martian Rock Formation

The results of a new study show Mars’s Medusae Fossae Formation is the largest known explosive volcanic deposit in the solar system.


V. Geophysical Research Letters

1.Interdecadal sea level variations in the Pacific: Distinctions between the tropics and extratropics

Long tide gauge records from Fremantle and San Diego are used to examine interdecadal sea level fluctuations and their relationship to Pacific climate variability. The sea level difference between the tide gauges and the Southern Oscillation Index (SOI) provide a consistent depiction of trade wind variations along the equator over the past century. The sea level difference and SOI exhibit weak interdecadal variability prior to the late 1970s, followed by an extended 40‐year period of high levels at San Diego and low at Fremantle, and low SOI levels signifying weakened equatorial trade winds. By referencing the tide gauge records to global mean sea level, we infer that Pacific trade winds exhibited weak departures from mean conditions on interdecadal time scales prior to the late 1970s, and that a prolonged El Ni?o‐like lull dominated the tropics at the end of the century. A recent shift suggests that the trades are reverting back to the El Ni?o‐like state. These tropical interdecadal variations have counterparts in the extratropical North Pacific after the 1970s, as captured by the Pacific Decadal Oscillation, but the early twentieth century quiescent phase in the tropical Pacific is not reflected in the extratropics, which exhibits more energetic oscillatory behavior over the same time span.


2.Greenland Ice SheetHigher nonlinearity of ice flow significantly reduces estimated basal motion

In times of warming in polar regions, the prediction of ice sheet discharge is of utmost importance to society, because of its impact on sea level rise. In simulations the flow rate of ice is usually implemented as proportional to the differential stress to the power of the exponent n=3. This exponent influences the softness of the modeled ice, as higher values would produce faster flow under equal stress. We show that the stress exponent, which best fits the observed state of the Greenland Ice Sheet, equals n=4, Our results, which are not dependent on a possible basal sliding component of flow, indicate that most of the interior northern ice sheet is currently frozen to bedrock, except for the large ice streams and marginal ice.


3.Eddy Tracking in the Northwestern Indian Ocean during Southwest Monsoon Regimes

The northwestern Indian Ocean exhibits a relatively highly energetic eddy field during the southwest monsoon season between June and September. This study analyzes the seasonal and interannual variability of the eddy characteristics and their trajectories in the northwestern Indian Ocean using altimetric sea surface height observations from 1993 – 2014. Although the highest number of eddies is found in the Arabian Peninsula coastal region, the strongest eddies, characterized by large radii, amplitudes, and eddy kinetic energies are found along the Somali Current. Trajectories of anticyclonic and cyclonic eddies are investigated to provide insight on the generation and propagation of eddies of varying amplitudes. The largest annual eddy in the Somali Current system corresponds to the Great Whirl (GW), for which the year‐to‐year variability with respect to shape, size, generation, and propagation were examined, as was the development of these characteristics over the GW's lifetime.


4.Security of deep groundwater in the coastal Bengal Basin revealed by tracers

Uncertainty persists regarding the vulnerability of deep groundwater across Asia's megadeltas. In the coastal Bengal Basin aquifer system, shallow groundwater (<100 m) commonly features high salinity or arsenic concentrations, and deep, better‐quality, groundwater supplies drinking water to >80 million people. Here we report new radiocarbon evidence from a network of nine dedicated, multi‐level monitoring wells which indicates residence times of between 103 and 104 years for groundwater at depths >150 m. Modern groundwater detected in some deep abstraction wells using anthropogenic tracers (SF6, CFCs) is attributed to short‐circuiting of shallow groundwater within wells. Age‐depth profiles and hydrochemical data in monitoring wells confirm the regional resilience of deep groundwater to ingress of shallow contaminated groundwater. Our results are consistent with high regional anisotropy in the aquifer and support continued use of deep groundwater though the potential for leakage of shallow contaminated groundwater in deep abstraction wells requires careful monitoring.


VI. AGU Blogs

1.Exploring Fronts with Multiple Robots: In The Extreme

While it is not something you hear about every day, what I do is part of a long tradition (over a century) of qualitative research in organizations and workplaces. Anthropology has a research method called ethnography that is used to study culture among communities. Workgroups are small communities that in work ethnography we call “communities of practice,” including all kinds of work domains, such as transportation, policing, medicine, and computer technology. In the past 30 years, ethnographic researchers in the fields of Anthropology, Communication, Science and Technology Studies (STS), and Sociology have been studying how people work in work environments of science and exploration, including high-energy physics, space exploration, ocean science, planetary science, and artificial intelligence.


2.Pink salmon — too much of a good thing?

About a decade ago, biologists Alan Springer and Gus van Vliet noticed a similar pattern among tufted puffins in a well-studied colony on Buldir Island in the Aleutians. The puffins were laying eggs earlier in even-numbered years and later in odd years. They too wondered if pink salmon might be responsible, by leaving less food for the puffins.Though they are the smallest of the salmon, pinks are the dominant species in the North Pacific Ocean and Bering Sea. Pink salmon born in hatcheries, where professionals harvest eggs from wild salmon and rear them in captivity before releasing them in the ocean, have doubled in numbers since 1990.


3.Exploring Fronts with Multiple Robots: Quiet Sense of Accomplishment

Sensors, actuators, and communication devices are currently pervasive in the cities we live in, and we are definitely evolving towards the “Internet of Things.” This has the potential to improve our quality of life by providing unprecedented capabilities to measure, for example, the quality of the air, among other parameters. The problem is that “instrumenting” cities and human developments is simply not enough to “evaluate” the health of Earth’s life support system. The oceans are an important component of this life support system, and we are still lacking the tools and technologies to study the status of the system’s overall health and functioning. This is even more critical because the oceans are deceptively large and “powerful” from space, but are in fact a “fragile” thin layer of water, with an average depth of 4km in a planet with over 6,000km radius. In fact, all water on Earth would fit in a sphere with a diameter of 860 miles. This is why we need to develop sustained ocean studies with unprecedented spatial and temporal resolution. Ships alone cannot help to achieve these levels of resolution, scale, and economic feasibility.



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