I.Climate Change
1. Preparing for the Future: Climate Products and Models for India
Kick-off Workshop of Indo-Norwegian Project PREPARE; Bergen, Norway, 27–31 March 2017
https://eos.org/meeting-reports/preparing-for-the-future-climate-products-and-models-for-india
2. Polar Satellite Launch Eases Concerns of Weather Data Gap
Joint Polar Satellite System-1 is the first in a series of planned polar-orbiting satellites to provide critical weather forecasting data. Two follow-on satellites, however, face uncertain funding.
https://eos.org/articles/polar-satellite-launch-eases-concerns-of-weather-data-gap
II. Hazards & Disasters
1. Looking Inside an Active Italian Volcano
Scientists use 3-D imaging to reveal Solfatara crater’s inner plumbing.
https://eos.org/research-spotlights/looking-inside-an-active-italian-volcano
2. Mystery Quakes May Be Among World’s Longest-Lived Aftershocks
New evidence about where a major earthquake struck central Washington State 145 years ago raises the possibility that today’s unusually frequent quakes in the area still echo that 1872 event.
https://eos.org/articles/mystery-quakes-may-be-among-worlds-longest-lived-aftershocks
III. Ocean Sciences
1. Satellites Accurately Capture Ocean Salinity in the Arctic
On-the-ground measurements are notoriously difficult in the harsh environment of the Arctic, but satellites could help close the gap in measuring sea surface salinity.
https://eos.org/research-spotlights/satellites-accurately-capture-ocean-salinity-in-the-arctic
2. Is Global Warming Suppressing Canonical El Niño?
A study explores the relationship between diverse El Niño events and the background state of the tropical Pacific.
https://eos.org/editor-highlights/is-global-warming-suppressing-canonical-el-nino
IV.Biogeosciences
1. Oceans May Produce Twice as Much Organic Matter as Usually Measured
Researchers study how oceans respire carbon, reexamining a critical part of the global carbon cycle.
V.Hydrology, Cryosphere & Earth Surface
1. Groundwater Use Could Be Significant Source of Carbon Dioxide
A new study estimates U.S. groundwater depletion could be responsible for releasing 1.7 million metric tons (3.8 billion pounds) of carbon dioxide to the atmosphere every year.
https://eos.org/scientific-press/groundwater-use-could-be-significant-source-of-carbon-dioxide
VI.Geophysical Research Letters
1. The Impact of the AMOC Resumption in the Western South Atlantic Thermocline at the Onset of the Last Interglacial
After glacial terminations, large amounts of heat and salt were transferred from low to high latitudes, which is a crucial phenomenon for the reestablishment of the Atlantic Meridional Overturning Circulation (AMOC). However, how different glacial terminations evolved in the (sub)tropics is still poorly documented. Here we use foraminifera oxygen (δ18O) and carbon (δ13C) stable isotopes to show that the North Atlantic heat piracy, following the AMOC resumption at the early Last Interglacial, affected the thermocline δ18O levels of the subtropical western South Atlantic. Because of the cooling imposed by this process, glacial δ18O persisted in the thermocline for ~7 kyr after the onset of the Last Interglacial, dampening the effect of sea level rise usually imprinted on foraminifera δ18O during terminations. Faunal composition and δ13C also suggest the existence of a colder and thicker South Atlantic Central Water coeval with the AMOC recovery. This process apparently did not occur during the last deglaciation.
http://onlinelibrary.wiley.com/doi/10.1002/2017GL074457/full
2. Decomposition of the Mean Barotropic Transport in a High-Resolution Model of the North Atlantic Ocean
We show how a barotropic shallow water model can be used to decompose the mean barotropic transport from a high-resolution ocean model based on the vertically averaged momentum equations. We apply the method to a high-resolution model of the North Atlantic for which the local vorticity budget is both noisy and dominated by small spatial scales. The shallow water model acts as an effective filter and clearly reveals the transport driven by each term. The potential energy (joint effect of baroclinicity and bottom relief) term is the most important for driving transport, including in the northwest corner, while mean flow advection is important for driving transport along f/H contours around the Labrador Sea continental slope. Both the eddy momentum flux and the mean flow advection terms drive significant transport along the pathway of the Gulf Stream and the North Atlantic Current.
http://onlinelibrary.wiley.com/doi/10.1002/2017GL074825/full
3. Algae Drive Enhanced Darkening of Bare Ice on the Greenland Ice Sheet
Surface ablation of the Greenland ice sheet is amplified by surface darkening caused by light-absorbing impurities such as mineral dust, black carbon, and pigmented microbial cells. We present the first quantitative assessment of the microbial contribution to the ice sheet surface darkening, based on field measurements of surface reflectance and concentrations of light-absorbing impurities, including pigmented algae, during the 2014 melt season in the southwestern part of the ice sheet. The impact of algae on bare ice darkening in the study area was greater than that of nonalgal impurities and yielded a net albedo reduction of 0.038 ± 0.0035 for each algal population doubling. We argue that algal growth is a crucial control of bare ice darkening, and incorporating the algal darkening effect will improve mass balance and sea level projections of the Greenland ice sheet and ice masses elsewhere.
http://onlinelibrary.wiley.com/doi/10.1002/2017GL075958/full
4. The Signature of Southern Hemisphere Atmospheric Circulation Patterns in Antarctic Precipitation
We provide the first comprehensive analysis of the relationships between large-scale patterns of Southern Hemisphere climate variability and the detailed structure of Antarctic precipitation. We examine linkages between the high spatial resolution precipitation from a regional atmospheric model and four patterns of large-scale Southern Hemisphere climate variability: the southern baroclinic annular mode, the southern annular mode, and the two Pacific-South American teleconnection patterns. Variations in all four patterns influence the spatial configuration of precipitation over Antarctica, consistent with their signatures in high-latitude meridional moisture fluxes. They impact not only the mean but also the incidence of extreme precipitation events. Current coupled-climate models are able to reproduce all four patterns of atmospheric variability but struggle to correctly replicate their regional impacts on Antarctic climate. Thus, linking these patterns directly to Antarctic precipitation variability may allow a better estimate of future changes in precipitation than using model output alone.
http://onlinelibrary.wiley.com/doi/10.1002/2017GL075998/full
5. Diapycnal Fluxes of Nutrients in an Oligotrophic Oceanic Regime: The South China Sea
Nutrients from depth have been hypothesized as a primary source of new nutrients that sustain new productivity in oligotrophic oceans; however, the flux is challenging to quantify. Here we show for a first time in the oligotrophic South China Sea an extremely low diapycnal dissolved inorganic nitrogen (DIN) flux as 1.8 × 10−4 mmol m−2 d−1 in the nutrient-depleted layer (NDL) above the nutricline, where other nutrient supplies sustain the new production. Here higher phosphate and silicate fluxes relative to DIN than Redfield stoichiometry further indicate N-limited biological productivity and additional removal of DIN by diatoms. Below the NDL across the nutricline to the base of euphotic zone, termed as nutrient replete layer, the DIN flux is three orders of magnitude larger and sufficient in supporting the export production therein. Here higher DIC flux relative to DIN than Redfield stoichiometry further infers DIC excess in the upper ocean.
http://onlinelibrary.wiley.com/doi/10.1002/2017GL074921/full
6. Floating Algae Blooms in the East China Sea
A floating algae bloom in the East China Sea was observed in Moderate Resolution Imaging Spectroradiometer (MODIS) imagery in May 2017. Using satellite imagery from MODIS, Visible Infrared Imaging Radiometer Suite, Geostationary Ocean Color Imager, and Ocean Land Imager, and combined with numerical particle tracing experiments and laboratory experiments, we examined the history of this bloom as well as similar blooms in previous years and attempted to trace the bloom source and identify the algae type. Results suggest that one bloom origin is offshore Zhejiang coast where algae slicks have appeared in satellite imagery almost every February–March since 2012. Following the Kuroshio Current and Taiwan Warm Current, these “initial” algae slicks are first transported to the northeast to reach South Korea (Jeju Island) and Japan coastal waters (up to 135°E) by early April 2017, and then transported to the northwest to enter the Yellow Sea by the end of April. The transport pathway covers an area known to be rich in Sargassum horneri, and spectral analysis suggests that most of the algae slicks may contain large amount of S. horneri. The bloom covers a water area of ~160,000 km2 with pure algae coverage of ~530 km2, which exceeds the size of most Ulva blooms that occur every May–July in the Yellow Sea. While blooms of smaller size also occurred in previous years and especially in 2015, the 2017 bloom is hypothesized to be a result of record-high water temperature, increased light availability, and continuous expansion of Porphyra aquaculture along the East China Sea coast.
http://onlinelibrary.wiley.com/doi/10.1002/2017GL075525/full
VII. AGU Blogs
1. What is so interesting about submarine volcanoes?
Jagged piles of molten rock, sulfurous smoke, exploding gaseous emissions, shifting landscapes, otherworldly creatures, scalding acidic fluids, swirling plumes of volcanic gasses and particles, and crushing pressure of the overlying sea: what is not to like about active submarine volcanoes? If that’s not reason enough for come to these places, how about an opportunity to understand one of earth’s most fundamental, dynamic, and yet rarely observed natural phenomena?
https://blogs.agu.org/thefield/2017/11/19/interesting-submarine-volcanoes/
2. Detecting landslide precursors from space
A holy grail of landslide studies is the ability to anticipate future behaviour by reliably detecting precursors. This is a highly fraught activity at any level, with the complexity of landslide behaviour rendering the interpretation of patterns of movement challenging. However, in situ detailed monitoring has yielded some interesting results over the years, and efforts continue. Meanwhile, developments in satellite technologies mean that detecting deformation from space is becoming increasingly possible. In particular, the InSAR technique, which uses techniques to compare repeated radar images, is very promising. The latest generation of ESA radar satellites, Sentinel 1A and 1B provide high quality imagery every six days in some cases.
https://blogs.agu.org/landslideblog/2017/11/17/landslide-precursors-1/
3. Groundwater recharge in the American west under climate change
Groundwater recharge in the Western U.S. will change as the climate warms–the dry southern regions will have less and the northern regions will have more, according to new research.
https://blogs.agu.org/geospace/2017/11/16/groundwater-recharge-american-west-climate-change/
VII. AGU News
1. AGU FALL MEETING IN NEW ORLEANS: ONLINE RESOURCES, EXPERT TOOLS NOW LIVE; EVENTS AND GENERAL SESSIONS
WASHINGTON, DC — Discover the latest Earth and space science news at the 50th annual AGU Fall Meeting this December, when about 24,000 attendees from around the globe are expected to assemble for the largest worldwide conference in the Earth and space sciences.
