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AGU Research Spotlight (May 03-May 09, 2018)

2018-05-11 08:27:28

I. Climate Change

1. Global Water Clarity: Continuing a Century-Long Monitoring

An approach that combines field observations and satellite inferences of Secchi depth could transform how we assess water clarity across the globe and pinpoint key changes over the past century.


2. Dynamic Ice Sheet and Sea Level Response to Past Climate Change

PALSEA2 Workshop; Playa del Carmen, Quintana Roo, Mexico, 6–9 November 2017


3. Improving Tropical Cyclone Predictions in the Gulf of Mexico

The National Oceanic and Atmospheric Administration’s newest High Resolution Atmospheric Model captures the influence of intraseasonal oscillations on tropical cyclone activity.


II. Hazards & Disasters

1. White House Seeks Input to Update Space Weather Strategy

Space weather can affect many technologies and infrastructures that society relies on. The White House seeks public input to inform the next steps to better prepare the Nation for this hazard.


2. A Better Way to Predict the Indian Monsoon

A new study finds that including Himalayan topography and land-atmosphere interactions improves climate models.


3. Sea Level Rise Threatens Hundreds of Wastewater Treatment Plants

Untreated sewage could affect 5 times more people than direct flooding, a new study shows.


III. Biogeosciences

1. It’s So UnFAIR!

A recent paper in JGR: Biogeosciences demonstrates that sharing data has positive benefits not just for the scientific community but also for the one doing the sharing.


IV. Ocean Sciences

1. What’s the Best Way to Responsibly Collect Ocean Data?

Evolving and Sustaining Oceans Best Practices Workshop; Paris, France, 15–17 November 2017


V. Hydrology, Cryosphere & Earth Surface

1. Satellite Data Archives Reveal Unrecorded Himalayan Floods

Almost 30 years’ worth of Landsat observations created a comprehensive inventory of catastrophic floods caused by glacial lakes bursting through their rock dams.


2. Calibrating Hydrological Models by Satellite

Hydrological models are usually calibrated using observations of streamflow, but a new method uses remotely sensed land surface temperature for this purpose.


VI. Planetary Sciences

1. New Lander en Route to Probe the Red Planet’s Interior

The Mars InSight mission aims to answer key planetary science questions about seismicity, meteorite impacts, and the formation of rocky planets.


VII. Geophysical Research Letters

1. To What Extent Multidecadal Changes in Morphology and Fluvial Discharge Impact Tide in a Convergent (Turbid) Tidal River

Understanding nonstationary tides in tidal rivers is a major contemporary challenge. In particular, the response of river tides to natural developments in the estuary remains poorly investigated. This study analyzes the evolution of tidal characteristics over the last six decades in the Garonne Tidal River (GTR, SW France), in order to explore the effect of natural and human‐induced morphological and hydrological changes on river tides. The tidal Garonne is an excellent example, as it has been subject to decreasing river discharges, natural morphological changes, and gravel extraction. Tidal range (TR), distortion (AM4/AM2), and asymmetry direction (2?M2‐?M4) were calculated at four locations from the water level time series of 1953, 1971, 1982, 1994, 2005, and 2014. The annual time series of M2 and M4 amplitudes and phases were obtained through complex demodulation. Results reveal that both TR and 2?M2‐?M4 have increased since the 1950s. River flow modulates TR and AM4/AM2 significantly. A long‐term decrease in summer discharges from 200?±?50 to 100?±?50 m3 s?1 would increase TR by +11.5% in the upper GTR. Natural morphological changes amplified TR and 2?M2‐?M4 by up to +12–15% between 1953 and 2014.


2. Recently Accelerated Oxygen Consumption Rates Amplify Deoxygenation in the Baltic Sea

Many coastal seas suffer from expanding bottom‐water deoxygenation and hypoxia primarily because of excessive nutrient loads from land. The Baltic Sea in northern Europe has one of the largest anthropogenically induced oxygen‐deficient bottom zones in the world. Despite the decrease of nutrient supply after the 1980s, recently observed oxygen consumption rates are higher than ever observed, limiting the impact of natural ventilation by oxygen‐enriched saltwater intrusions. We have estimated oxygen consumption rates after saltwater inflows during subsequent stagnation periods from monitoring observations and model results for 1850–2015. In recent years, ventilating water that originates mainly from the surface layer has contained higher concentrations of organic matter, zooplankton, and higher trophic levels. As a result, oxygen consumption in the water column has increased relatively more than oxygen consumption in the sediment, primarily due to respiration of zooplankton and higher trophic levels. Subsequently, natural ventilation has become less effective in alleviating hypoxia, instead amplifying deoxygenation of the deep water.


3. The Biological Pump and Seasonal Variability of pCO2 in the Southern Ocean: Exploring the Role of Diatom Adaptation to Low Iron

Iron is known to limit primary production in the Southern Ocean (SO). To cope with the lack of this micronutrient, diatoms, a dominant phytoplankton group in this oceanic region, have been shown in cultures to have developed an original adaptation strategy to maintain efficient growth rates despite very low cellular iron quotas, even in low light conditions. Using a global ocean biogeochemical model, we explored the consequences of this physiological adaptation for the biological pump and the seasonal variability of both surface chlorophyll concentrations and surface partial pressure of carbon dioxide (pCO2) in this key region for global climate. In the model, we implemented a low intracellular Fe:C requirement in the SO for diatoms uniquely. This results in an increase of 10% in the relative contribution of diatoms to total SO primary production. The biological pump is also strengthened, which increases the biological contribution to the seasonal evolution of pCO2 relative to the thermodynamic component. Therefore, the seasonal evolution of both surface chlorophyll and surface pCO2 is significantly impacted, with a marked improvement, in our model, in the SO polar zone compared to the observations. Our model study underscores the potentially important consequences that this adaptive physiological behavior of diatoms could have on marine biogeochemistry in the SO. It is thus critical to improve our understanding of the physiology of this key phytoplankton group, in particular in the SO.


4. Wind Stress Mediated Variability of the Filchner Trough Overflow, Weddell Sea

The Filchner Trough (FT) is a key site for exchange of water masses between the Weddell Sea continental shelf and the deep ocean. Cold and dense Ice Shelf Water (ISW), a precursor for Antarctic Bottom Water, flows north along the FT and overflows the Filchner Sill. Although access of warm water to the Weddell Sea continental shelf is limited due to the presence of the Antarctic Slope Front, southward transport of warm water is facilitated through the FT. We use moored current meters from the Filchner Sill region to show that the monthly scale variability of the ISW overflow is connected to the variability of the alongslope wind stress upstream. Periods with significant correlation between the wind and ISW overflow are characterized by (I) wind directed along the continental slope, (II) high ISW overflow speed, and (III) high variability in the 16–64 day period band for wind and current. We propose that a recirculation of the slope current, associated with the Antarctic Slope Front, may occur in the FT during periods of strong wind forcing, and that such recirculation could explain the correlation between the wind stress and the ISW overflow. We further show that an increased wind stress along the continental slope leads to increased current speed within the slope current and the Antarctic Coastal Current, with possible implications for the on‐shore heat transport.


5. Episodic Reversal of Autumn Ice Advance Caused by Release of Ocean Heat in the Beaufort Sea

High‐resolution measurements of the air‐ice‐ocean system during an October 2015 event in the Beaufort Sea demonstrate how stored ocean heat can be released to temporarily reverse seasonal ice advance. Strong on‐ice winds over a vast fetch caused mixing and release of heat from the upper ocean. This heat was sufficient to melt large areas of thin, newly formed pancake ice; an average of 10 MJ/m2 was lost from the upper ocean in the study area, resulting in ~3–5 cm pancake sea ice melt. Heat and salt budgets create a consistent picture of the evolving air‐ice‐ocean system during this event, in both a fixed and ice‐following (Lagrangian) reference frame. The heat lost from the upper ocean is large compared with prior observations of ocean heat flux under thick, multiyear Arctic sea ice. In contrast to prior studies, where almost all heat lost goes into ice melt, a significant portion of the ocean heat released in this event goes directly to the atmosphere, while the remainder (~30–40%) goes into melting sea ice. The magnitude of ocean mixing during this event may have been enhanced by large surface waves, reaching nearly 5 m at the peak, which are becoming increasingly common in the autumn Arctic Ocean. The wave effects are explored by comparing the air‐ice‐ocean evolution observed at short and long fetches, and a common scaling for Langmuir turbulence. After the event, the ocean mixed layer was deeper and cooler, and autumn ice formation resumed.


6. Metrics for the Evaluation of the Southern Ocean in Coupled Climate Models and Earth System Models

The Southern Ocean is central to the global climate and the global carbon cycle, and to the climate's response to increasing levels of atmospheric greenhouse gases, as it ventilates a large fraction of the global ocean volume. Global coupled climate models and earth system models, however, vary widely in their simulations of the Southern Ocean and its role in, and response to, the ongoing anthropogenic trend. Due to the region's complex water‐mass structure and dynamics, Southern Ocean carbon and heat uptake depend on a combination of winds, eddies, mixing, buoyancy fluxes, and topography. Observationally based metrics are critical for discerning processes and mechanisms, and for validating and comparing climate and earth system models. New observations and understanding have allowed for progress in the creation of observationally based data/model metrics for the Southern Ocean. Metrics presented here provide a means to assess multiple simulations relative to the best available observations and observational products. Climate models that perform better according to these metrics also better simulate the uptake of heat and carbon by the Southern Ocean. This report is not strictly an intercomparison, but rather a distillation of key metrics that can reliably quantify the “accuracy” of a simulation against observed, or at least observable, quantities. One overall goal is to recommend standardization of observationally based benchmarks that the modeling community should aspire to meet in order to reduce uncertainties in climate projections, and especially uncertainties related to oceanic heat and carbon uptake.



1. Powerful hurricanes strengthen faster now than 30 years ago

Hurricanes that intensify rapidly – a characteristic of almost all powerful hurricanes – do so more strongly and quickly now than they did 30 years ago, according to a new study. Many factors are at play, but the chief driver of more rapid hurricane intensification is a natural climate cycle known as the Atlantic Multidecadal Oscillation (AMO) that affects water temperatures in the Atlantic Ocean where hurricanes form, according to the study’s authors.


2. Breathing lunar dust could pose health risk to future astronauts

Future astronauts spending long periods of time on the Moon could suffer bronchitis and other health problems by inhaling tiny particles of dust from its surface, according to new research. A new study finds simulated lunar soil is toxic to human lung and mouse brain cells. Up to 90 percent of human lung cells and mouse neurons died when exposed to dust particles that mimic soils found on the Moon’s surface.


3. Meltwater lakes not only summer phenomenon: Warm wind melts snow in Antarctica in winter as well

Even though the sun does not shine in Antarctica in winter, in some places snow on the glaciers can melt. The cause: warm wind.


4. 2/3 pass rate on determining geopetal “up”

Yesterday I finished a new GIGAmacro image, a view of a chunk of Tonoloway Formation showing what I thought were exquisite graded beds in these Silurian shallow-water carbonates. Closer examination revealed several other primary sedimentary structures with geopetal value: desiccation cracks (“mud cracks”) in cross-section, with their V’s opening upward, and a small instance of scouring and filling, where the pre-existing mud deposit was eroded by energetic sand transport, and sand filled the resulting hollow. Three for the price of one, in terms of determining younging direction. There were also some ambiguous mud cracks, and at least one example where the V pointed the wrong way. But the preponderance of the evidence was pretty clear to me, and I thought it was a good teaching example. I deliberately imaged it with bedding “vertical” in the frame of the image.


5. Communicating about rare and common species

On March 19, in a grassy enclosure at the Ol Pejeta Conservancy in Kenya, a northern white rhinoceros named Sudan died. He was the last of his kind. Were you surprised by this news? Probably not, because you already know this story: biodiversity is declining, species are vanishing, more and more animals and plants are in peril.


6. 6.9 Quake Rattles Hawaii’s Nerves as Kilauea Rumbles.

A 6.9 quake hit the Big Island of Hawaii Friday afternoon as lava fountains erupted in a housing development near Volcanoes National park. The NPS has now closed the park and the area has been evacuated. Kilauea is a shield volcano and not like Mt. St. Helens which is a strato-volcano. While a Strato-volcano can have an explosive eruption that throws ash miles into the air, shield types volcanos tend to produce large lava flows.




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