Long-term soil moisture datasets at high spatial resolution are important in agricultural, hydrological, and climatic applications. The soil moisture estimates can be achieved using satellite remote sensing observations. However, the satellite soil moisture data are typically available at coarse spatial resolutions (~ several tens of km), therefore require further downscaling. Different satellite soil moisture products have to be conjointly employed in developing a consistent time-series of high resolution soil moisture, while the discrepancies amongst different satellite retrievals need to be resolved. This study aims to downscale three different satellite soil moisture products, the Soil Moisture and Ocean Salinity (SMOS, 25 km), the Soil Moisture Active Passive (SMAP, 36 km) and the SMAP-Enhanced (9 km), and to conduct an inter-comparison of the downscaled results. The downscaling approach is developed based on the relationship between the diurnal temperature difference and the daily mean soil moisture content. The approach is applied to two sub-catchments (Krui and Merriwa River) of the Goulburn River catchment in the Upper Hunter region (NSW, Australia) to estimate soil moisture at 1 km resolution for 2015. The three coarse spatial resolution soil moisture products and their downscaled results will be validated with the in-situ observations obtained from the Scaling and Assimilation of Soil Moisture and Streamflow (SASMAS) network. The spatial and temporal patterns of the downscaled results will also be analysed. This study will provide the necessary insights for data selection and bias corrections to maintain the consistency of a long-term high resolution soil moisture dataset. The results will assist in developing a time-series of high resolution soil moisture data over the south-eastern Australia.

Pore water freshening (i.e., decreases in dissolved Cl) has been documented in marine sediments along most active margins, with the migration of deep fluids or methane hydrate dissociation often invoked as sources of freshening in the sediment column. During D/V JOIDES Resolution Expedition 379T in 2019, two new sites (J1005 and J1006) were cored near ODP Site 1233 (41°S), adjacent to a seafloor mound venting structure. The three sites are less than 10 km apart but show marked differences in pore water chemistry and methane hydrate occurrence. The extent of Cl decrease is a function of distance from the mound, with the strongest freshening occurring at the closest site (J1006), which is the only site where methane hydrate was observed. Methane fluxes follow the same pattern, suggesting a common control. Increasing oxygen and decreasing hydrogen isotopes point to deep mineral bound water as the primary source of freshening near the mound, with fluids originating ~2.5 km below seafloor near the décollement. Secondary influences from methane hydrate dissociation and ash diagenesis also appear to influence regional pore water chemistry. The variability in pore water freshening suggests that fluid migration and eventual expulsion at the venting structure follows narrow pathways, likely along faults within the forearc complex. The migration of deep, gas-charged fluids may also support methane hydrate saturations greater than in situ organic carbon diagenesis would allow, but nonetheless consistent with geophysical estimates. Together, the data highlight an important link between fluid migration and methane hydrate formation on the Chilean Margin.

A document by Miriam Gauntlett. Click on the document to view its contents.

The response of atmospheric variability to the Tibetan Plateau (TP) snow cover (TPSC) at interannual to decadal time-scales has been extensively investigated. However, the response of the atmosphere to the subseasonal variability of the TPSC has been largely ignored. Here, we found that the subseasonal variability of the TPSC revealed by daily data can serve as an indicator of East Asian atmospheric circulation on medium-range time-scales (approximately 3–7 days in advance). The subseasonal variability of the TPSC influences the upper-level regional atmospheric circulations, especially the East Asia upper-level westerly jet stream (EAJS), during wintertime. The variability of the TPSC modulates the land surface thermal conditions over the TP, which acts as an elevated cooling source in the middle troposphere during wintertime. The upper-level geopotential height is affected by the TPSC and then the zonal wind. As a result, the EAJS is influenced.

Particle sinking velocity is an important determinant of carbon transport and sequestration to the deep-sea. It is however technically challenging to measure in situ particle sinking velocities. Recently, methods based on the radioactive pairs, (234Th-238U and 210Po-210Pb) were developed to estimate average sinking velocity (ASV), along the classical carbon export flux estimates. The influence of ASVs on key metrics of the biological carbon pump such as (i) the particle export efficiency (defined as the proportion of PP being exported below the surface ocean) (ii) carbon export fluxes and attenuation, still remain uncertain and need to be further evaluated. ASVs are calculated in five biogeochemically contrasting sites: high latitude (Irminger Basin; Scotia Sea), temperate (PAP site) and oligotrophic (BATS, Equator) North Atlantic. ASVs are also calculated for different bloom stages (bloom - post bloom) in the North Atlantic and at the start of the bloom in two contrasting sites in the Southern Ocean (Scotia Sea). A systematic increase of ASVs with depth, inversely correlated to carbon flux attenuation, is detected. We assess whether the increase in ASV with depth is correlated with either temperature or community structure (phytoplankton and/or zooplankton). Evidences of ASV correlation with carbon export efficiency are detected, but they vary strongly with season and location, e.g. very distinct relationships are found for the results from Scotia Sea, likely driven by zooplankton abundance.

In this work we extend previous studies by exploring the potential impact of spectroscopic knowledge along with atmospheric state knowledge on retrievals of carbon dioxide (XCO2) and methane (XCH4) column amounts from laser differential absorption spectrometer (LAS) measurements. This has been done for multiple CO2 absorption lines in the 1.57 and 2.05 μm regions, and for CH4 in the 1.65 μm region. One such potential source of error in performing XCO2 retrievals is modeled surface pressure. Since it has been proposed to derive surface pressure from LAS-based O2 measurements in lieu of modeled surface pressure for use in XCO2 retrievals as a means of error reduction, our past work has also attempted to characterize and quantify potential improvements in XCO2 retrieval error associated with O2-derived surface pressure for a set of CO2 and O2 absorption line combinations. All of our previous analyses have relied on a radiative-transfer-based simulation framework utilizing the Line-by-Line Radiative Transfer Model (LBLRTM), version 12.2 (release date November, 2012). LBLRTM has undergone several upgrades since version 12.2, to include updates to its line parameter database, updates to its continuum model, and bug fixes. Our current work revisits our prior assessments using the latest version of LBLRTM (version 12.8) and comparisons are provided and discussed.

Wave breaking transfers momentum between waves to currents. In doing so it dissipates wave energy and affects long-term dispersion and transport of tracers, Wave breaking also affects the transfer of wind stresses to the ocean and is a major player in ocean acoustics, the dynamics of near-surface gas exchanges and the dynamics of phytoplankton and buoyant pollutants. Progressive waves were generated numerically using Gerris [6]. The velocity field was then used to estimate Lagrangian parcel dynamics in the neighborhood of the breaking event. The trans- port generated by the breaking events is shown to be significant, when compared to the wave-generated residual flow, as captured by the Stokes drift. We formulate a parametrization of the break- ing velocity based upon an analysis of the Largrangian dynamics of fluid parcels. Further, we describe how the breaking velocity is incorporated in the vortex force formulation of wave current interactions [1, 2].

Most climate change impacts are linked to terrestrial vegetation productivity, carbon stocks and land use change. Changes in land use and climate drive the dynamics of terrestrial carbon cycle. These carbon cycle dynamics operate at different spatial and temporal scales. Quantification of the spatial and temporal variability of carbon flux has been challenging because land-atmosphere-carbon exchange is influenced by many factors, including but not limited to, land use change and climate change and variability. The study of terrestrial carbon cycle, mainly gross primary product (GPP), net ecosystem exchange (NEE), soil organic carbon (SOC) and ecosystem respiration (Re) and their interactions with land use and climate change, are critical to understanding the terrestrial ecosystem. The main objective of this study was to examine the interactions among land use, climate change and terrestrial carbon cycling in the state of Texas using satellite measurements. We studied GPP, NEE, Re and SOC distributions for five selected major land covers and all ten climate zones in Texas using Soil Moisture Active Passive (SMAP) carbon products. SMAP Carbon products (Res=9 km) were compared with observed CO2 flux data measured at EC flux site on Prairie View A&M University Research Farm. Results showed the same land cover in different climate zones has significantly different carbon sequestration potentials. For example, cropland of the humid climate zone has higher (-228 g C/m2) carbon sequestration potentials than the semiarid climate zone (-36 g C/m2). Also, shrub land in the humid zone and in the semiarid zone showed high (-120 g C/m2) and low (-36 g C/m2) potentials of carbon sequestration, respectively, in the state. Overall, the analyses indicate CO2 storage and exchange respond differently to various land covers, and environments due to differences in water availability, root distribution and soil properties.

River networks are important features in surface hydrology. However, accurately representing river networks in spatially distributed hydrologic and Earth system models is often sensitive to the model’s spatial resolution. Specifically, river networks are often misrepresented because of the mismatch between the model’s spatial resolution and river network details, resulting in significant uncertainty in the projected flow direction. In this study, we developed a topological relationships-based river network representation method for spatially distributed hydrologic models. This novel method uses (1) graph theory algorithms to simplify real-world vector-based river networks and assist in mesh generation; and (2) a topological relationship-based method to reconstruct conceptual river networks. The main advantages of our method are that (1) it combines the strengths of vector-based and DEM raster-based river network extraction methods; and (2) it is mesh-independent and can be applied to both structured and unstructured meshes. This method paves a path for advanced terrain analysis and hydrologic modeling across different scales.

Following the radioactive fall out of the 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, radiocesium (Cs-137) contaminated soils of forests, uplands, rice paddies and other land uses released contaminated sediments onto neighboring areas and into the creeks and rivers in Iitate Village, Japan. The study used conventional and Cs-137 fingerprinting techniques to determine runoff and suspended sediment discharges to assess the small and large-scale soil redistribution dynamics within contributing areas in two watersheds. Also, we attempted to use Cs-137 fingerprinting to identify spatial and temporal patterns of erosion, transport and sedimentation on hillslopes within those watersheds. Tributaries near the outlet of the 30 km2 Hiso watersheds were simulated at the hillslope and watersheds using the process-based Water Erosion Prediction Project (WEPP) model and the Geospatial Interface for WEPP (GeoWEPP). Besides the simulation of historic soil redistribution events, a particular emphasis was the identification and assessment of various land use and cover changes on the past soil redistribution. Results of the analysis in the post-fallout landscapes enables scientists and farmers as well as natural resources and disaster managers to investigate the consequences of active and passive land use and cover changes on the runoff and sediment dynamics at the plot, hillslope and watershed scales. Especially the behavior of Cs-137 contaminated clay particles in soils and sediments seem to be the key for the success of the measurement, modeling and management techniques. The result of this study has the potential to assist decision and policymaking for stakeholders not only in areas that were impacted by the contamination through radioactive fallout.

The sea surface temperature (SST) is one of the essential parameters to understand the climate change in the Arctic. Saildrone, an advanced autonomous surface vehicle (ASV), has proven to be a useful tool for providing sufficiently accurate SST data at high latitudes. Here, data from two Saildrones, deployed in the Arctic in the summer of 2019, are used to investigate the diurnal variability of upper ocean thermal structure. An empirical cool skin effect model with dependence on the wind speed with new coefficients was generated. Several local large diurnal warming events were observed, the amplitudes of warming in the skin layer > 5 K, rarely reported in previous studies. Furthermore, the warming signals could persist beyond one day. For those cases, it was found surface warm air suppressed the surface turbulent heat loss to maintain the persistence of diurnal warming under low wind conditions. Salinity also plays an important role in the formation of upper ocean density stratification during diurnal warming at high latitudes. A less salty surface layer was likely created by precipitation or melting sea ice, providing favorable conditions for the formation of upper ocean stratification. By comparing with two prognostic diurnal warming models, the simulations match reasonably well with those from the Saildrone for moderate wind speed conditions but exhibit large differences at low winds. Both schemes show significant negative biases in the early morning and late afternoon. It is necessary to further improve the model schemes when applied at high latitudes.

Ocean geochemical tracers such as radiocarbon, protactinium and thorium isotopes, and noble gases are widely used to constrain a range of physical and biogeochemical processes in the ocean. However their routine simulation in global ocean circulation and climate models is hindered by the computational expense of integrating them to a steady state. Here, a new approach to this long-standing “spin-up’ problem is introduced to efficiently compute equilibrium distributions of such tracers in seasonally-forced models. Based on “Anderson Acceleration’, a sequence acceleration technique developed in the 1960s to solve nonlinear integral equations, the new method is entirely “black box’ and offers significant speed-up over conventional direct time integration. Moreover, it requires no preconditioning, ensures tracer conservation and is fully consistent with the numerical time-stepping scheme of the underlying model. It thus circumvents some of the drawbacks of other schemes such as matrix-free Newton Krylov that have been proposed to address this problem. An implementation specifically tailored for the batch HPC systems on which ocean and climate models are typically run is described, and the method illustrated by applying it to a variety of geochemical tracer problems. The new method, which provides speed-ups by over an order of magnitude, should make simulations of such tracers more feasible and enable their inclusion in climate change assessments such as IPCC.

Ice sheet melting into the Southern Ocean can change the formation and properties of the Antarctic Bottom Water (AABW). Climate models generally mimic ice sheet melting by adding uniformly-distributed freshwater fluxes in the Southern Ocean. Uniform fluxes misrepresent the heterogeneous Antarctic ice sheet melting patterns, and could bias AABW representation in models. We use a global ocean and sea-ice model to explore whether the spatial distribution and increases in freshwater fluxes can alter AABW properties, formation, and the Antarctic sea-ice area. We find that a realistic spatially varying flux sustains AABW with higher salinities compared to simulations with uniform meltwater fluxes. Finally, we show that a ~ 20% increase in ice sheet melting can trigger AABW freshening and Antarctic sea-ice expansion rates similar to those observed in the Southern Ocean since 1980, suggesting that the increasing Antarctic meltwater discharge can drive the observed AABW freshening and the Antarctic sea-ice expansion.

Geodetic observations after large subduction earthquakes reflect multiple postseismic processes, including megathrust relocking. What the timing of relocking is, and how well observations constrain it, is unclear. It has been inferred to explain some observed landward motion that occurs within months. It has also been considered unable to explain other, greater landward motion, including off the coast of Japan beginning weeks after the 2011 Tohoku earthquake, which is attributed to postseismic relaxation. We use generic, 3D numerical models to show that relocking, particularly of the shallow interface, is needed for postseismic relaxation to produce landward motion on the tip of the overriding plate. We argue that this finding is consistent with previous simulations that implicitly relock the megathrust where afterslip is not included, that the Tohoku megathrust thus relocked within less than two months of the earthquake, and that the shallow megathrust probably behaves as a true, unstably sliding asperity.

In the text “Complexity”, I create a definition for complexity and a standard to measure how complex a specific entity is. By using this method, we can easily compare the complexity of different objects and explain clearly why certain objects are more complicated than others. Moreover, I also suggest that we shall use Complexity to replace the Entropy because there is no such thing as order or disorder in the real world.

Accurate and dynamic mapping of water and ice surfaces is directly useful to navigation and lake ice cover monitoring to study climate change. Water and ice maps are also useful for various scientific applications such as atmospheric correction of satellite imagery, remote sensing of water quality, and as input data for hydrological, weather and climate models. The existing literature shows that multi-spectral satellite imagery, as provided by Sentinel-2 and Landsat-8, provides a very effective means to discriminate between water, land, and ice. However, most studies focus either on very specific cases (a specific lake for instance), or on general cases but without complex and yet very frequent cases such as turbid waters and salt lakes which can be confused with snow and ice. The Copernicus High-Resolution Snow and Ice Monitoring Service provides an operational Sentinel-2 ice and water classification product at 20m resolution but with a lot of confusion on the aforementioned cases. Using a database of 31 fully hand-labelled Sentinel-2 L2A atmospherically corrected images, and machine learning SVM and RandomForest methods, the current study shows that the classification of land, water, ice, snow, turbid waters, salt lake categories can be achieved with an accuracy over 93%. It is also shown that the atmospheric correction has little to no impact on the results, as training and evaluating from L1C top of the atmosphere images instead of L2A images yields very similar results. This last find is very useful as it means that very accurate surface masks can now be provided to atmospheric processors and may therefore considerably improve the quality of atmospherically corrected images when compared to the current usage of static masks.

A document by Björn Sonnenschein. Click on the document to view its contents.

We reviewed 80 studies from behavior sciences, environmental psychology, resource management, and health communication fields to learn why some voluntary message campaigns sustained conservation behaviors. We found past campaigns reduced residential water use by 0.6% to 54% and reductions lasted less than 1 year. The most effective campaigns included a public plea, social comparison information, easy-to-adopt conservation tips, and linked to additional resources. Effective campaigns also targeted different socio-psychological drivers, such as intention, altruism, peer pressure, and perception of ease or difficulty in adopting new conservation behaviors. To help users sustain water-saving behaviors for longer periods of time, we suggest managers (a) learn user’s intentions and informational preferences, (b) launch feedback programs during critical periods such as a drought, (c) state what the water authority is doing to achieve the conservation goal, (d) customize message content based on a user’s attitude and information preferences, (e) target one easy-to-implement conservation action at a time, (f) praise efficient behavior, (g) communicate through a variety of internet, paper, and other mediums, (h) regularly update message contents, (i) encourage users to publicly commit to conservation, (j) publicly recognize water savers, and (k) allow users to share their conservation experiences.