Search Results (9)

Sustained reductions in terrestrial water storage (TWS) have been observed globally using Gravity Recovery and Climate Experiment (GRACE) satellite data since 2002. However, the underlying mechanisms remain incompletely understood due to limited record lengths and data discontinuity. Recently, explainable artificial intelligence (XAI) has provided robust tools for unveiling dynamics in complex Earth systems. In this study, we employed a deep learning technique (Long Short-Term Memory network, LSTM) to reconstruct global TWS dynamics, filling gaps in the GRACE record. We then utilized the Local Interpretable Model-agnostic Explanations (LIME) method to uncover the underlying mechanisms driving observed TWS reductions. Our results reveal a consistent decline in the global mean TWS over the past 22 years (2002–2024), primarily influenced by precipitation (17.7%), temperature (16.0%), and evapotranspiration (10.8%). Seasonally, the global average of TWS peaks in April and reaches a minimum in October, mirroring the pattern of snow water equivalent with approximately a one-month lag. Furthermore, TWS variations exhibit significant differences across latitudes and are driven by distinct factors. The largest declines in TWS occur predominantly in high latitudes, driven by rising temperatures and significant snow/ice variability. Mid-latitude regions have experienced considerable TWS losses, influenced by a combination of precipitation, temperature, air pressure, and runoff. In contrast, most low-latitude regions show an increase in TWS, which the model attributes mainly to increased precipitation. Notably, TWS losses are concentrated in coastal areas, snow- and ice-covered regions, and areas experiencing rapid temperature increases, highlighting climate change impacts. This study offers a comprehensive framework for exploring TWS variations using XAI and provides valuable insights into the mechanisms driving TWS changes on a global scale. Full article

Global surface pressure, terrestrial water storage models, and seabed pressure grids provide valuable support for studying the mechanisms of the nonlinear motion behind GNSS stations. These data allow for the precise identification and analysis of displacement effects caused by environmental loads. This study analyzes GNSS coordinate time series data from 186 ITRF reference stations worldwide over a 10-year period, thoroughly examining the magnitude, spatial distribution, and impact of hydrological, atmospheric, and non-tidal oceanic loading on nonlinear motion. The results indicate that the atmospheric loading effects had a magnitude of approximately ±5 mm in the up (U) direction and ±1 mm in the east (E) and north (N) directions. Moreover, the impact of atmospheric loading on station displacements was more pronounced in high-latitude regions compared with mid- and low-latitude regions. Secondly, the hydrological loading showed a magnitude of approximately ±5 mm in the U direction and ±0.8 mm in the E and N directions, with inland areas causing larger displacements than coastal regions. Furthermore, the non-tidal oceanic loading induced displacements with magnitudes of approximately ±0.5 mm in the E and N directions and ±2 mm in the U direction, significantly affecting stations in the nearshore areas more than inland stations. Subsequently, this study analyzes the corrective effects of environmental loads on the coordinate time series. The average correlation coefficients between the E, N, and U directions and the coordinate time series were 0.35, 0.31, and 0.52, respectively. After removing the displacements caused by environmental loads, the root mean square (RMS) values of the coordinate time series decreased by 85.5% in the E direction, 77.4% in the N direction, and 89.8% in the U direction, with average reductions of 6.2%, 4.4%, and 16.7%, respectively. Lastly, it also comprehensively assesses the consistency between environmental loads and coordinate time series from the perspectives of the optimal noise model, velocity and uncertainty, and amplitude and phase. This study demonstrates that the geographic location of a station is closely related to the impact of environmental loads, with a significantly greater effect in the vertical direction than that in the horizontal direction. By correcting for environmental loads, the accuracy of the coordinate time series can be significantly enhanced. Full article

Estuary ecosystems serve as crucial connectors between terrestrial and marine environments, thus playing vital roles in maintaining the ecological balance of coastal marine ecosystems. In recent years, the eutrophication in estuaries caused by aquaculture sewage has been revealed, highlighting the necessity to understand its influence on the nutrient conditions and carbon storage of estuaries. In this study, δ¹⁵N and δ¹⁸O were used to indicate the contribution of aquaculture-derived sewage to dissolved inorganic nitrogen in Zhangjiang Estuary, and δ¹³C and C:N ratio were used to reveal its effects on the particulate organic matter. The major results are as follows: (1) Aquaculture water contributed 62~86% and 60~100% of the total nitrate and ammonium in Zhangjiang Estuary, respectively, and the drainage periods of the cultured species has a great influence on the content and composition of dissolved inorganic nitrogen. (2) Aquaculture water was also the major source of particulate organic matter (24~33% of the total content) here, most of which may be derived from crab ponds. (3) The imports of nutrients by aquaculture water may potentially regulate particulate organic matter in Zhangjiang Estuary by promoting the growth of phytoplankton and zooplankton. Our study revealed the coupling effects of aquaculture activities on the nitrogen and carbon storage in an estuarine ecosystem. It also indicates that isotopes may be efficient in the monitoring of a coastal environment, which may further aid the management of inshore cultivation. Full article

Investigations of the geochemical compositions of geothermal water, as well as their movements and geneses, are of great significance for the exploration and exploitation of hydrothermal resources. In Zhongshan City, a southern city in Guangdong Province, large amounts of geothermal heat have been discovered. The results of investigations show that the hydrochemical types of geothermal water in the study area are Cl-Na·Ca and Cl-Na. H-O isotopes are basically near the atmospheric precipitation line, and the calculated recharge elevation of geothermal water ranges from 716 to 822 m, which is close to the altitude of the North Peak Mountain in Taishan City. The deep thermal storage temperature ranges from 95.32 to 149.71 °C, and the depth of the thermal cycle ranges from 2638.57 m to 4581.07 m. The genetic model of the geothermal water in this area is that, at favorable structural positions with satisfied water storage conditions, the mixture of atmospheric precipitation and seawater that circulates deep in Earth is heated by terrestrial heat flow under actions such as deep heat exchange and water–rock reactions to leach the salt, finally forming the highly mineralized geothermal water that uplifts out of the surface along faults and crops. The formation of the genetic model of geothermal water will provide a geological basis and technical support for the efficient development and utilization of geothermal resources in Zhongshan City and the coastal area of Southeast China. Full article

A unique variety of wetlands known as coastal wetlands that connect terrestrial and marine ecosystems is crucial to reducing and adapting to climate change as well as the advancement of human culture. However, the coastal wetland ecosystem is currently in danger as a result of the increasing intensity of human activity, and wetland restoration and reconstruction have garnered a lot of interest. The differentiated ecological restoration strategies based on ecosystem service change analysis can provide a reference for the effective management and sustainability of coastal wetland ecosystems. The InVEST model and ArcGIS were used to analyze the spatiotemporal changes in ecosystem services before and after the implementation of coastal wetland restoration policies based on remote sensing image data, meteorological and soil data, etc. The ecological restoration pattern of coastal wetlands was divided, and the corresponding ecological restoration strategies were proposed in this study. The following are the results: (1) there are still many wetlands that have been converted to non-wetlands following the implementation of the wetland restoration policy, and the ecosystem services as a whole exhibit a rising and then falling trend, with a rise from 2005 to 2015, a fall in 2015 due to the creation of Hangzhou Bay New District, and a slight improvement to 2020. Among them, the water yield increased continuously, the carbon storage fluctuated, and the habitat quality did not improve significantly. (2) The hot spots of ecosystem services were concentrated in the south and southeast of the study area, with no obvious cold spots. (3) By comprehensively analyzing the changes and spatial patterns of ecosystem services, the coastal wetlands on the south bank of Hangzhou Bay were divided into an ecological conservation zone, a green development zone, and an ecological restoration zone at the township level, and corresponding optimization strategies were proposed. The results can provide a reference for the fine-grained and differentiated management of regional ecosystem services. Full article

Land use changes and mounting water demands reduce freshwater inflows into estuaries, impairing estuarine ecosystems and accelerating coastal seawater intrusion. However, determining minimum river inflows for management guidelines is hampered by a lack of ecosystem-flow link data. This study describes the development of freshwater inflow guidelines for the Wami Estuary, combining scarce river flow data, hydrological modeling, inferring natural salinity regime from vegetation zonation and investigating freshwater requirements of people/wildlife. By adopting the Building Blocks Methodology, a detailed Environmental Flows Assessment was performed to know the minimum water depth/quality seasonal requirements for vegetation, terrestrial/aquatic wildlife and human communities. Water depth requirements were assessed for drought and normal rainfall years; corresponding discharges were obtained by a hydrological model (HEC-RAS) developed for the river channel upstream of estuary. Recommended flows were well within historically occurring flows. However, given the rapidly increasing water demand coupled with reduction in basin water storage due to deforestation/wetland loss, it is critical to ensure these minimum flows are present, without which essential ecosystem services (fisheries, water quality, mangrove forest resources and wildlife/tourism) will be jeopardized. The EFA process is described in painstaking detail to provide a reference for undertaking similar studies in data-poor regions worldwide. Full article

With the increasing vulnerability of groundwater resources, especially in coastal regions, there is a growing need to monitor changes in groundwater storage (GWS). Estimations of GWS have been conducted extensively at regional to global scales using GRACE and GRACE-FO observations. The major goal of this study was to evaluate the applicability of uninterrupted monthly GRACE-derived terrestrial water storage (TWS_GRACE) records in facilitating detection of long- and short-term hydroclimatic events affecting the GWS in a coastal area. The TWS_GRACE data gap was filled with reconstructed values from multi-linear regression (MLR) and artificial neural network (ANN) models and used to estimate changes in GWS in the Texas coastal region (Gulf Coast and Carrizo–Wilcox Aquifers) between 2002 and 2019. The reconstructed TWS_GRACE, along with soil moisture storage (SMS) from land surface models (LSMs), and surface water storage (SWS) were used to estimate the GRACE-derived GWS (GWS_GRACE), validated against the GWS estimated from groundwater level observations (GWS_well) and extreme hydroclimatic event records. The results of this study show: (1) Good agreement between the predicted TWS_GRACE data gaps from the MLR and ANN models with high accuracy of predictions; (2) good agreement between the GWS_GRACE and GWS_well records (CC = 0.56, p-value < 0.01) for the 2011–2019 period for which continuous GWL_well data exists, thus validating the approach and increasing confidence in using the reconstructed TWS_GRACE data to monitor coastal GWS; (3) a significant decline in the coastal GWS_GRACE, at a rate of 0.35 ± 0.078 km³·yr⁻¹ (p-value < 0.01), for the 2002–2019 period; and (4) the reliable applicability of GWS_GRACE records in detecting multi-year drought and wet periods with good accuracy: Two drought periods were identified between 2005–2006 and 2010–2015, with significant respective depletion rates of −8.9 ± 0.95 km³·yr⁻¹ and −2.67 ± 0.44 km³·yr⁻¹ and one wet period between 2007 and 2010 with a significant increasing rate of 2.6 ± 0.63 km³·yr⁻¹. Thus, this study provides a reliable approach to examine the long- and short-term trends in GWS in response to changing climate conditions with significant implications for water management practices and improved decision-making capabilities. Full article

The study introduces a new atmosphere-land-aquifer coupled model and evaluates terrestrial water storage (TWS) simulations for Southern California between 2007 and 2016. It also examines the relationship between precipitation, groundwater, and soil moisture anomalies for the two primary aquifer systems in the study area, namely the Coastal Basin and the Basin and Range aquifers. Two model designs are introduced, a partially-coupled model forced by reanalysis atmospheric data, and a fully-coupled model, in which the atmospheric conditions were simulated. Both models simulate the temporal variability of TWS anomaly in the study area well (R² ≥ 0.87, P < 0.01). In general, the partially-coupled model outperformed the fully-coupled model as the latter overestimated precipitation, which compromised soil and aquifer recharge and discharge. Simulations also showed that the drought experienced in the area between 2012 and 2016 caused a decline in TWS, evapotranspiration, and runoff of approximately 24%, 65%, and 11%, and 20%, 72% and 8% over the two aquifer systems, respectively. Results indicate that the models first introduced in this study can be a useful tool to further our understanding of terrestrial water storage variability at regional scales. Full article

The measurement of total basin discharge along coastal regions is necessary for understanding the hydrological and oceanographic issues related to the water and energy cycles. However, only the observed streamflow (gauge-based observation) is used to estimate the total fluxes from the river basin to the ocean, neglecting the portion of discharge that infiltrates to underground and directly discharges into the ocean. Hence, the aim of this study is to assess the total discharge of the Yangtze River (Chang Jiang) basin. In this study, we explore the potential response of total discharge to changes in precipitation (from the Tropical Rainfall Measuring Mission—TRMM), evaporation (from four versions of the Global Land Data Assimilation—GLDAS, namely, CLM, Mosaic, Noah and VIC), and water-storage changes (from the Gravity Recovery and Climate Experiment—GRACE) by using the terrestrial water budget method. This method has been validated by comparison with the observed streamflow, and shows an agreement with a root mean square error (RMSE) of 14.30 mm/month for GRACE-based discharge and 20.98 mm/month for that derived from precipitation minus evaporation (P − E). This improvement of approximately 32% indicates that monthly terrestrial water-storage changes, as estimated by GRACE, cannot be considered negligible over Yangtze basin. The results for the proposed method are more accurate than the results previously reported in the literature. Full article