Changes in climate patterns are dramatically influencing some agricultural areas. Arid, semi‐arid and coastal agricultural areas are especially vulnerable to climate change impacts on soil salinity. ...Inventorying and monitoring climate change impacts on salinity are crucial to evaluate the extent of the problem, to recognize trends and to formulate irrigation and crop management strategies that will maintain the agricultural productivity of these areas. Over the past three decades, Corwin and colleagues at the U.S. Salinity Laboratory (USSL) have developed proximal sensor and remote imagery methodologies for assessing soil salinity at multiple scales. The objective of this paper is to evaluate the impact climate change has had on selected agricultural areas experiencing weather pattern changes, with a focus on the use of proximal and satellite sensors to assess salinity development. Evidence presented in case studies for Californiaʼs San Joaquin Valley (SJV) and Minnesotaʼs Red River Valley (RRV) demonstrates the utility of these sensor approaches in assessing soil salinity changes due to changes in weather patterns. Agricultural areas are discussed where changes in weather patterns have increased root‐zone soil salinity, particularly in areas with shallow water tables (SJV and RRV), coastal areas with seawater intrusion (e.g., Bangladesh and the Gaza Strip) and water‐scarce areas potentially relying on degraded groundwater as an irrigation source (SJV and Murray‐Darling River Basin). Trends in salinization due to climate change indicate that the infrastructure and protocols to monitor soil salinity from field to regional to national to global scales are needed.
Highlights
Climate change will have a negative impact on agriculture, particularly in arid regions.
Proximal/remote sensors are useful to assess climate change impact on soil salinity across scales.
Salt‐water intrusion, shallow water tables and degraded water reuse will increase soil salinity.
Infrastructure and protocols to monitor soil salinity across multiple scales are needed.
This study examines the impact of ocean advection and surface freshwater flux on the non‐seasonal, upper‐ocean salinity variability in two climate model simulations with eddy‐resolving and ...eddy‐parameterized ocean components (HR and LR, respectively). We assess the realism of each simulation by comparing their sea surface salinity (SSS) variance with satellite and Argo float estimates. In the extratropics, the HR variance is about five times larger than that in LR and agrees with Argo. In turn, the extratropical satellite SSS variance is smaller than that from HR and Argo by about a factor of two, potentially caused by the insufficient resolution of radiometers to capture mesoscale features and their low sensitivity to SSS in cold waters. Using a simplified salinity conservation equation for the upper‐50‐m ocean, we find that the advection‐driven variance in HR is, on average, 10 times larger than the surface flux‐driven variance, reflecting the action of mesoscale processes.
Plain Language Summary
This study explores the importance of ocean currents, evaporation, and rainfall for driving changes in the salt concentration in the upper ocean (known as salinity) in two climate model simulations with differing ocean resolutions. The high‐resolution model (HR) simulates ocean currents with dimensions of tens of km, while the low‐resolution model (LR) can only simulate currents with hundreds of km in size. When comparing their simulated sea surface salinity variations with those captured by satellites and autonomous floats from the Argo array, the salinity variability in the high‐resolution model is similar to the Argo data at mid to high latitudes and about five times stronger than that in the low‐resolution model. The satellite data show a variability two times smaller than HR and Argo in the same regions, potentially due to their insufficient spatial resolution at higher latitudes and their low sensitivity to the surface salinity in cold waters. Using a simple equation describing the conservation of salinity in the upper ocean, we have shown that small‐scale ocean currents drive most of the salinity variability in HR, while in LR, ocean currents play a much smaller role.
Key Points
We investigate how advection and surface flux affect upper‐50‐m salinity variance in eddy‐resolving and eddy‐parameterized climate models
The extratropical variance in the eddy‐resolving run matches Argo and is much larger than in the eddy‐parameterized run and satellite data
The larger upper‐ocean salinity variance in the eddy‐resolving run is predominantly driven by mesoscale ocean processes
Soil salinization has become one of the major environmental and socioeconomic issues globally and this is expected to be exacerbated further with projected climatic change. Determining how climate ...change influences the dynamics of naturally-occurring soil salinization has scarcely been addressed due to highly complex processes influencing salinization. This paper sets out to address this long-standing challenge by developing data-driven models capable of predicting primary (naturally-occurring) soil salinity and its variations in the world's drylands up to the year 2100 under changing climate. Analysis of the future predictions made here identifies the dryland areas of South America, southern and western Australia, Mexico, southwest United States, and South Africa as the salinization hotspots. Conversely, we project a decrease in the soil salinity of the drylands in the northwest United States, the Horn of Africa, Eastern Europe, Turkmenistan, and west Kazakhstan in response to climate change over the same period.
While the global water cycle has been studied previously based on land and open ocean studies, here we use coastal satellite sea surface salinity (SSS) data to show that in global aggregate, SSS ...variations near coasts are strongly correlated with global water cycle variability driven by El Niño Southern Oscillation (ENSO). This is a significant finding as we demonstrate that open ocean SSS variability is not as sensitive to ENSO and global water cycle variability as the coastal oceans at interannual timescales. Aggregated global coastal SSS could therefore be used as a proxy for detection of changes in the large‐scale cycling of water between the oceans and continents. Moreover, we identify major potential “hotspots” on land and in the coastal ocean that tend to drive global coastal salinity variability, and which may consequently be most sensitive to future physical and biological impacts of water cycle changes on the coastal oceans.
Plain Language Summary
While the global water cycle has been studied from the land perspective and the open ocean perspective, we offer a novel analysis showing that the global coastal zone provides an opportunity to monitor aggregated water cycle variability. We show that most global sea surface salinity variability is concentrated near the coasts and that coastal salinity variations at interannual time scales are highly correlated to El Niño Southern Oscillation (ENSO), with global river discharge being the connecting mechanism. Coastal salinity can thus be used to monitor global water cycle variability at interannual time scales. With global warming, changes in the water cycle and in ENSO's intensity and frequency are expected. The global coastal oceans may be where these changes are most detectable in aggregate, and coastal salinity measurements can be used as a valuable proxy by communities monitoring these changes.
Key Points
Sea surface salinity (SSS) variability is more than 30 times higher at the coast than in the open ocean
Coastal SSS variability is driven primarily by the terrestrial water cycle at interannual scales, unlike open ocean SSS
El Niño Southern Oscillation impacts coastal SSS via modulation of precipitation on land and subsequent river runoff
Global mapping of soil salinity change Ivushkin, Konstantin; Bartholomeus, Harm; Bregt, Arnold K. ...
Remote sensing of environment,
09/2019, Letnik:
231
Journal Article
Recenzirano
Odprti dostop
Soil salinity increase is a serious and global threat to agricultural production. The only database that currently provides soil salinity data with global coverage is the Harmonized World Soil ...Database, but it has several limitations when it comes to soil salinity assessment. Therefore, a new assessment is required. We hypothesized that combining soil properties maps with thermal infrared imagery and a large set of field observations within a machine learning framework will yield a global soil salinity map. The thermal infrared imagery acts as a dynamic variable and allows us to characterize the soil salinity change. For this purpose we used Google Earth Engine computational environment. The random forest classifier was trained using 7 soil properties maps, thermal infrared imagery and the ECe point data from the WoSIS database. In total, six maps were produced for 1986, 2000, 2002, 2005, 2009, 2016. The validation accuracy of the resulting maps was in the range of 67–70%. The total area of salt affected lands by our assessment is around 1 billion hectares, with a clear increasing trend. Comparison with 3 studies investigating local trends of soil salinity change showed that our assessment was in correspondence with 2 of these studies. The global map of soil salinity change between 1986 and 2016 was produced to characterize the spatial distribution of the change. We conclude that combining soil properties maps and thermal infrared imagery allows mapping of soil salinity development in space and time on a global scale.
•Soil properties maps combined with thermal imagery can be used to map soil salinity.•Thermal imagery can act as a dynamic variable.•Soil salinisation is increasing on global scale.
Soil salinity is a major threat to agricultural sustainability and a global food security. Until now, most research has concentrated around stomatal limitation to photosynthesis, while non-stomatal ...limitations receiving much less attention. This work summarizes the current knowledge of impact of salinity on chloroplast metabolism and operation and finding viable solutions to minimize it. The major topics covered are: (1) the key targets of the photosynthetic apparatus under salt stress; (2) a tolerance of PSII to salt stress and its repair; (3) salinity effects on biochemistry of CO
2
fixation and its regulation; (4) ionic requirements for optimal operation of chloroplasts; and (5) ion transport systems in chloroplasts that optimize chloroplast performance under hostile saline conditions. We show that enhancing plant capacity for protection by modifying PSI cyclic electron transport, redistribution of electron transport between photosystems, thylakoid membrane composition and photosynthetic antioxidant enzymes activity may be a promising way to improve tolerance to salt stress under real-field condition. It is concluded that revealing the molecular nature of chloroplast ion transporters and understanding the modes of their operation will ensure the future sustainability of the world agriculture and the prospects of biological phytoremediation of salinized land via using salt-tolerant crop germplasm.
Abstract
A nonlinear empirical method, called the generalized regression neural network with the fruit fly optimization algorithm (FOAGRNN), is proposed to estimate subsurface salinity profiles from ...sea surface parameters in the Pacific Ocean. The purpose is to evaluate the ability of the FOAGRNN methodology and satellite salinity data to reconstruct salinity profiles. Compared with linear methodology, the estimated salinity profiles from the FOAGRNN method are in better agreement with the measured profiles at the halocline. Sensitivity studies of the FOAGRNN estimation model shows that, when applied to various types of sea surface parameters, latitude is the most significant variable in estimating salinity profiles in the tropical Pacific Ocean (correlation coefficient
R
greater than 0.9). In comparison, sea surface temperature (SST) and height (SSH) have minimal effects on the model. Based on FOAGRNN modeling, Pacific Ocean three-dimensional salinity fields are estimated for the year 2014 from remote sensing sea surface salinity (SSS) data. The performance of the satellite-based salinity field results and possible sources of error associated with the estimation methodology are briefly discussed. These results suggest a potential new approach for salinity profile estimation derived from sea surface data. In addition, the potential utilization of satellite SSS data is discussed.
Soil salinization is one of the major environmental stressors hampering the growth and yield of crops all over the world. A wide spectrum of physiological and biochemical alterations of plants are ...induced by salinity, which causes lowered water potential in the soil solution, ionic disequilibrium, specific ion effects, and a higher accumulation of reactive oxygen species (ROS). For many years, numerous investigations have been made into salinity stresses and attempts to minimize the losses of plant productivity, including the effects of phytohormones, osmoprotectants, antioxidants, polyamines, and trace elements. One of the protectants, selenium (Se), has been found to be effective in improving growth and inducing tolerance against excessive soil salinity. However, the in-depth mechanisms of Se-induced salinity tolerance are still unclear. This review refines the knowledge involved in Se-mediated improvements of plant growth when subjected to salinity and suggests future perspectives as well as several research limitations in this field.
Salt Tolerance Mechanisms of Plants van Zelm, Eva; Zhang, Yanxia; Testerink, Christa
Annual review of plant biology,
04/2020, Letnik:
71, Številka:
1
Journal Article
Recenzirano
Crop loss due to soil salinization is an increasing threat to agriculture worldwide. This review provides an overview of cellular and physiological mechanisms in plant responses to salt. We place ...cellular responses in a time- and tissue-dependent context in order to link them to observed phases in growth rate that occur in response to stress. Recent advances in phenotyping can now functionally or genetically link cellular signaling responses, ion transport, water management, and gene expression to growth, development, and survival. Halophytes, which are naturally salt-tolerant plants, are highlighted as success stories to learn from. We emphasize that (
a
) filling the major knowledge gaps in salt-induced signaling pathways, (
b
) increasing the spatial and temporal resolution of our knowledge of salt stress responses, (
c
) discovering and considering crop-specific responses, and (
d
) including halophytes in our comparative studies are all essential in order to take our approaches to increasing crop yields in saline soils to the next level.
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