I. Ocean Sciences
1. Tracking Nitrogen in Arctic Plants
Prevailing nutrient uptake models do not fit Arctic plants. Scientists test a new option that overcomes older models’ shortcomings.
2. Warm Waters in West Antarctica
A recent paper in Reviews of Geophysics describes the atmospheric and oceanic processes that are causing ice loss in the Antarctic.
3. How Will Climate Change Affect the California Current Upwelling?
The results of new simulations that account for internal climate variability contrast with previous projections of how this vital West Coast current will respond to anthropogenic warming.
II. Hazards & Disasters
1. Deforestation Effects as Different as Night and Day
Study investigates how deforestation can cause different land surface temperature effects depending on the time of day.
2. Wildfires Pollute Much More Than Previously Thought
Naturally burning timber and brush launch fine particles into the air that are a hazard to human health.
3. Mapping Dengue Fever Hazard with Machine Learning
Researchers develop a predictive software system to identify city-specific, dengue fever risk areas amid a global increase in cases.
III. Hydrology, Cryosphere & Earth Surface
1. Shedding Light on Intermittent Rainfall
A study provides a new modeling method to simulate rain when it pours and when it doesn’t.
2. Global Atmospheric Observations May Need Tweaking for Turbulence
A new study that overturns an 80-year-old assumption about atmospheric turbulence may finally resolve discrepancies in observations of atmospheric heat, water vapor, and carbon.
IV. Planetary Sciences
1. Innovative Postage Stamp Celebrates Upcoming Total Solar Eclipse
The eclipse expert whose photographs appear on the stamp said he is thrilled about the opportunities that the stamp and the eclipse afford to excite people about science.
2. Mysterious Particle Beams Found over Jupiter’s Poles
The unexpected character of the beams, revealed by NASA’s Juno spacecraft, suggests that the processes that produce Jupiter’s auroras are unlike those on Earth.
3. Lab Tests Probe Carbon Planets’ Inner Dynamics
Thermal convection in deep interiors could be more vigorous in carbide planets than in comparably sized silicate planets, according to new high-pressure measurements of silicon carbide.
V. Geophysical Research Letters
1. The effect of differential rotation on Jupiter's low-degree even gravity moments
The close-by orbits of the ongoing Juno mission allow measuring with unprecedented accuracy Jupiter's low-degree even gravity moments J2, J4, J6, and J8. These can be used to better determine Jupiter's internal density profile and constrain its core mass. Yet the largest unknown on these gravity moments comes from the effect of differential rotation, which gives a degree of freedom unaccounted for by internal structure models. Here considering a wide range of possible internal flow structures and dynamical considerations, we provide upper bounds to the effect of dynamics (differential rotation) on the low-degree gravity moments. In light of the recent Juno gravity measurements and their small uncertainties, this allows differentiating between the various models suggested for Jupiter's internal structure.
2. On the direction of the Poynting flux associated with equatorial plasma depletions as derived from Swarm
Magnetic and electric field observations from the European Space Agency Swarmmission are used to report the direction of electromagnetic energy flux associated with equatorial plasma depletions. Contrary to expectations, the observations suggest a general interhemispheric Poynting flux rather than concurrent flows at both hemispheres toward or away from the equator. Of high interest is a particular behavior noticed over the region with the largest variation in the magnetic declination. This is a Poynting flux flowing mainly into the southern magnetic hemisphere about between 60°W and 30°E and into the northern magnetic hemisphere between 110°W and 60°W. The abrupt change in the flow direction at 60°W is suggested to be caused by an asymmetry between the hemispheres on the ionospheric conductivity, likely due to the influence of thermospheric winds and the presence of the South Atlantic Anomaly.
3. Connecting Antarctic sea ice to deep-ocean circulation in modern and glacial climate simulations
Antarctic sea-ice formation plays a key role in shaping the abyssal overturning circulation and stratification in all ocean basins, by driving surface buoyancy loss through the associated brine rejection. Changes in Antarctic sea ice have therefore been suggested as drivers of major glacial-interglacial ocean circulation rearrangements. Here, the relationship between Antarctic sea ice, buoyancy loss, deep-ocean stratification, and overturning circulation is investigated in Last Glacial Maximum and preindustrial simulations from the Paleoclimate Modelling Intercomparison Project (PMIP). The simulations show substantial intermodel differences in their representation of the glacial deep-ocean state and circulation, which is often at odds with the geological evidence. We argue that these apparent inconsistencies can largely be attributed to differing (and likely insufficient) Antarctic sea-ice formation. Discrepancies can be further amplified by short integration times. Deep-ocean equilibration and sea-ice representation should, therefore, be carefully evaluated in the forthcoming PMIP4 simulations.
4. Building and breaking a large igneous province: An example from the High Arctic
The genesis of the Amerasia Basin in the Arctic Ocean has been difficult to discern due to overprint of the Cretaceous High-Arctic Large Igneous Province (HALIP). Based on detailed analysis of bathymetry data, new Arctic magnetic and gravity compilations, and recently published radiometric and seismic data, we present a revised plate kinematic model of the northernmost Amerasia Basin. We show that the smaller Makarov Basin is formed by rifting and seafloor spreading during the latest Cretaceous (to middle Paleocene). The opening progressively migrated into the Alpha Ridge structure, which was the focus of Early-to-Middle Cretaceous HALIP formation, causing breakup of the proto-Alpha Ridge into the present-day Alpha Ridge and Alpha Ridge West Plateau. We propose that breakup of the Makarov Basin was triggered by extension between the North America and Eurasian plates and possibly North Pacific plate rollback.
5. Winter-time variability of the eastern Arabian Sea: A comparison between 2003 and 2013
The eastern Arabian Sea (EAS) is a region of complex interplay between several spatially and temporally varying oceanographic processes. Using two sets of in situ data collected from the same stations, separated by a decade, we show that warming and cooling in the EAS were linked to the long-term variability of this region. Though the warming in the southern part of EAS was consistent with the basin-wide rise in sea surface temperature in the Arabian Sea (AS), the enhanced freshening was a remote response to episodic events mediated by the strengthening of interbasin exchange between Bay of Bengal and AS through East India Coastal Current and West India Coastal Current. The increased stratification in the southern part of EAS led to the decline in the chlorophyll over the decade. In contrast, enhanced chlorophyll in the northern part of the EAS over the decade was linked to the increased wind speed.
6. Decadal changes in Southern Ocean ventilation inferred from deconvolutions of repeat hydrographies
Changes in Southern Ocean ventilation imprint on dissolved gases, nutrients, radiocarbon, temperature, and salinity. We deconvolve tracer measurements for the distribution, , of times and locations of last ventilation using a maximum-entropy approach. Decadal changes of are quantified by deconvolving hydrographies measured during the early 1990s and again some 15 years later. Our analysis reveals coherent changes across the five meridional sections analyzed: The fraction of water younger than 30 years decreased by ～20% per decade south of 40°S in circumpolar deep water (CDW) and increased by ～10% per decade north of ～40°S in subantarctic mode water (SAMW). Ventilation locations shifted, with more water south of 40°S being ventilated north of the subantarctic front. These ventilation changes impacted CFC uptake, with concentrations south of 40°S less than (and north of 40°S higher than) expected for steady flow. The inferred changes imply increased SAMW formation and CDW upwelling consistent with strengthened westerly winds.
7. Land-sea thermal contrast determines the trend of Walker circulation simulated in atmospheric general circulation models
Strengthening or weakening of the Walker circulation can highly influence the global weather and climate variability by altering the location and strength of tropical heating. Therefore, there is considerable interest in understanding the mechanisms that lead to the trends in the Walker circulation intensity. Conventional wisdom indicates that a strengthening or weakening of the Walker circulation is primarily controlled by inhomogeneous sea surface temperature (SST) patterns across the tropical Pacific basin. However, we show that Atmospheric Model Intercomparison Project climate model simulations with identical SST forcing have different Walker circulation trends that can be linked to differences in land surface temperatures. More prominently, stronger land-sea thermal contrast leads to increases in the precipitation in South America as well as the sea level pressure in the eastern tropical Pacific through a local circulation, resulting in a strengthening of the Walker circulation trend. This implies that correctly simulating the land temperature in atmospheric models is crucial to simulating the intensity of the Walker circulation in the present climate as well as its future change.
VI. AGU Blogs
1. Fire & Rain, and Heat as Well.
Intense heat, with low humidity has led to a horrible catastrophe in Portugal. The hot and dry weather in Europe led to a firestorm in Portugal that killed at least 60 people. A strong upper level high pressure system will stay over the area tomorrow and little or no rain is in sight.
2. Clean Energy Powered 10% of America in March
Look at this graph. The Energy Information Administration data for March 2017 shows 10% of U.S. power came from wind and solar, a level unimaginable two decades ago. The graph below shows the clean power by state: Now, look at the death of coal: Clean Energy Is Winning The Price Race We are living through a total upheaval in the way the world produces energy, and clean energy is rapidly becoming …