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AGU Research Spotlight (Apr 05-Apr 11, 2018)

2018-04-13 10:12:41

I. Climate Change

1. Reconstructing Climate and Environment from Coral Archives

Tropical Coral Archives—Reconstructions of Climate and Environment Beyond the Instrumental Record at Society-Relevant Timescales; Bremen, Germany, 28 September 2017


2. How Ice Rafting Events Affect Asian Monsoon Hydroclimate

Cave stalagmites provide isotopic evidence that Bond events and Heinrich events have more variable effects on Asian monsoon hydroclimate during the last glacial period than during the Holocene.


3. Piecing Together the Big Picture on Water and Climate

A new database brings together water isotope data from many sources, providing an integrated resource for studying changes in Earth’s hydroclimate over the past 2,000 years.


II. Hazards & Disasters

1. Peering Beneath the Powder: Using Radar to Understand Avalanches

High-resolution radar images from Switzerland’s experimental test site show that snow temperature is a key factor in classifying avalanche behavior.


2. Increasing Radiation Levels May Challenge Space Exploration

New research shows that solar radiation levels are growing 10% faster than previously believed and that the radiation environment in space will worsen with time.


III. Biogeosciences

1. The Long Reach of El Ni?o’s Broom

Both the El Ni?o Southern Oscillation and natural variations in tropical Pacific weather conditions impact surface air quality in the Eastern United States.


IV. Hydrology, Cryosphere & Earth Surface

1. Spectral Surface Emissivity Improves Arctic Climate Simulation

Improving the representation of surface emissivity in the Community Earth System Model reduces its Arctic winter cold bias from 7 to 1 Kelvin degree.


V. Ocean Sciences

1. Dust Does Not Control Surface Ocean Productivity

The first continuous comparisons between daily atmospheric dust and ocean productivity measurements indicate that they are not correlated in the Gulf of Aqaba’s nutrient-limited ecosystem.


VI. Geophysical Research Letters

1. Assessing Phytoplankton Nutritional Status and Potential Impact of Wet Deposition in Seasonally Oligotrophic Waters of the Mid‐Atlantic Bight

To assess phytoplankton nutritional status in seasonally oligotrophic waters of the southern Mid‐Atlantic Bight, and the potential for rain to stimulate primary production in this region during summer, shipboard bioassay experiments were performed using natural seawater and phytoplankton collected north and south of the Gulf Stream. Bioassay treatments comprised iron, nitrate, iron + nitrate, iron + nitrate + phosphate, and rainwater. Phytoplankton growth was inferred from changes in chlorophyll a, inorganic nitrogen, and carbon‐13 uptake, relative to unamended control treatments. Results indicated the greatest growth stimulation by iron + nitrate + phosphate, intermediate growth stimulation by rainwater, modest growth stimulation by nitrate and iron + nitrate, and no growth stimulation by iron. Based on these data and analysis of seawater and atmospheric samples, nitrogen was the proximate limiting nutrient, with a secondary limitation imposed by phosphorus. Our results imply that summer rain events increase new production in these waters by contributing nitrogen and phosphorus, with the availability of the latter setting the upper limit on rain‐stimulated new production.


2. Evaluating Impacts of Recent Arctic Sea Ice Loss on the Northern Hemisphere Winter Climate Change

Wide disagreement among individual modeling studies has contributed to a debate on the role of recent sea ice loss in the Arctic amplification of global warming and the Siberian wintertime cooling trend. We perform coordinated experiments with six atmospheric general circulation models forced by the observed and climatological daily sea ice concentration and sea surface temperature. The results indicate that the impact of the recent sea ice decline is rather limited to the high‐latitude lower troposphere in winter, and the sea ice changes do not significantly lead to colder winters over Siberia. The observed wintertime Siberian temperature and corresponding circulation trends are reproduced in a small number of ensemble members but not by the multimodel ensemble mean, suggesting that atmospheric internal dynamics could have played a major role in the observed trends.


3. Growing land‐sea temperature contrast and the intensification of Arctic cyclones

Cyclones play an important role in the coupled dynamics of the Arctic climate system on a range of timescales. Modelling studies suggest that storminess will increase in Arctic summer due to enhanced land‐sea thermal contrast along the Arctic coastline, in a region known as the Arctic Frontal Zone (AFZ). However, the climate models used in these studies are poor at reproducing the present‐day Arctic summer cyclone climatology and so their projections of Arctic cyclones and related quantities, such as sea ice, may not be reliable. In this study we perform composite analysis of Arctic cyclone statistics using AFZ variability as an analogue for climate change. High AFZ years are characterised both by increased cyclone frequency and dynamical intensity, compared to low years. Importantly, the size of the response in this analogue suggests that GCMs may underestimate the response of Arctic cyclones to climate change, given a similar change in baroclinicity.


4. Increased winter‐mean wave height, variability and periodicity in the North‐East Atlantic over 1949‐2017

A 69‐year (1948‐2017) numerical weather and wave hindcast is used to investigate the interannual variability and trend of winter wave height along the west coast of Europe. Results show that the winter‐mean wave height, variability and periodicity all increased significantly in the northeast Atlantic over the last seven decades which primarily correlate with changes in the climate indices North Atlantic Oscillation (NAO) and West Europe Pressure Anomaly (WEPA) affecting atmospheric circulation in the North Atlantic. NAO and WEPA primarily explain the increase in winter‐mean wave height and periodicity, respectively, while both WEPA and NAO explain the increase in interannual variability. This increase in trend, variability and periodicity resulted in more frequent high‐energy winters with high NAO and/or WEPA over the last decades. The ability of climate models to predict the winter NAO and WEPA indices a few months ahead will be crucial to anticipate coastal hazards in this region.


5. Unprecedented 2015/2016 Indo‐Pacific Heat Transfer Speeds Up Tropical Pacific Heat Recharge

El Ni?o events are characterized by anomalously warm tropical Pacific surface waters and concurrent ocean heat discharge, a precursor of subsequent cold La Ni?a conditions. Here we show that El Ni?o 2015/2016 departed from this norm: despite extreme peak surface temperatures, tropical Pacific (30°N–30°S) upper ocean heat content increased by 9.6 ± 1.7 ZJ (1 ZJ = 1021 J), in stark contrast to the previous strong El Ni?o in 1997/1998 (?11.5 ± 2.9 ZJ). Unprecedented reduction of Indonesian Throughflow volume and heat transport played a key role in the anomalous 2015/2016 event. We argue that this anomaly is linked with the previously documented intensified warming and associated rising sea levels in the Indian Ocean during the last decade. Additionally, increased absorption of solar radiation acted to dampen Pacific ocean heat content discharge. These results explain the weak and short‐lived La Ni?a conditions in 2016/2017 and indicate the need for realistic representation of Indo‐Pacific energy transfers for skillful seasonal‐to‐decadal predictions.


6. Evidence for Extending Anomalous Miocene Volcanism at the Edge of the East Antarctic Craton

Using field observations followed by petrological, geochemical, geochronological, and geophysical data, we infer the presence of a previously unknown Miocene subglacial volcanic center ~230 km from the South Pole. Evidence of volcanism is from boulders of olivine‐bearing amygdaloidal/vesicular basalt and hyaloclastite deposited in a moraine in the southern Transantarctic Mountains. 40Ar/39Ar ages from five specimens plus U‐Pb ages of detrital zircon from glacial till indicate igneous activity 25–17 Ma. The likely source of the volcanism is a circular ?735 nT magnetic anomaly 60 km upflow from the sampling site. Subaqueous textures of the volcanics indicate eruption beneath ice or into water at the margin of an ice mass during the early Miocene. These rocks record the southernmost Cenozoic volcanism in Antarctica and expand the known extent of the oldest lavas associated with West Antarctic Rift system. They may be an expression of lithospheric foundering beneath the southern Transantarctic Mountains.


VII. AGU Blogs

1. Early climate action has big effect on rising sea levels

Rising sea levels will accelerate this century and beyond, exposing hundreds of millions of people to flooding and other coastal hazards by the year 2300. But acting early to lower greenhouse gas emissions can slow that rise, say scientists in two new studies in Earth’s Future, an open access journal published by the American Geophysical Union.


2. Infrasound recordings give scientists a peek inside volcano’s plume

High-resolution recordings of the powerful infrasound waves generated by an eruption at Ecuador’s Tungurahua volcano have given scientists a rare view inside the activity at the volcano’s mouth. The acoustic waves generated by the July 2013 eruption were one of the most powerful volcanic infrasound recordings ever captured. The low-frequency infrasound waves from the eruption are too low for human ears to hear but were as powerful as waves one meter (three feet) away from a jet engine.


3. Fatal landslides in 2017

I have now been able to complete the database of fatal landslides or 2017 (an increasingly challenging task given the commitments of my day job). This is the 15th full year in which I have compiled this dataset, which I formally wrote up in the journal Geology a few years ago.  I have written about this work many times before, and Melanie and I have a paper with the most recent analysis of the data under open peer review (please do take a look and leave a review if you have time).

In total in 2017 I recorded 453 landslides worldwide that caused loss of life, excluding landslides caused by earthquakes.  In total these caused 4,164 deaths.  The graph below shows the annual total number of fatal landslides since 2003.


4. North Cascade Winter Snowpack Status 2018

2018 Winter Freezing levels at Mount Baker (November 2017-March 2018).  The accumulation season on most Northern Hemisphere glaciers extends through April. The key benchmark for snowpack water assessment in alpine ranges is typically April 1, as that is the average maximum snowpack for an alpine range.  In 2018 the North Cascade Range had freezing levels above the long term mean, but at the 21st century mean.


5. Warsaw Icefield, King George Is., Antarctica Retreating from Shoreline

Warsaw Icefield, King George Island, Antarctica glacier retreat and nunatak expansion in 1989, 2001 and 2018 Landsat images. E=Ecology Glacier, B=Baranowski Glacier, W=Windy Glacier, 1989 terminus locations indicated by red arrows.  Point A & B are nunataks.  The Arctowski Polish Research Station is located on a relatively large ice-free oasis northeast of the Warsaw Icefield on King George Island, Antarctica.



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