This page has only limited features, please log in for full access.
A total of 388 surface sediment samples taken from the northern South China Sea (SCS) continental shelf were analyzed to characterize the signature of their rare earth elements (REEs). The average REEs concentration was 192.94 μg/g, with a maximum of 349.07 μg/g, and a minimum of 32.97 μg/g. The chondrite-normalized REEs pattern exhibits a remarkably light REEs accumulation, a relatively flat heavy REEs pattern, and a negative Eu anomaly. We subdivided the study area into three zones using the characteristics of REEs and statistical characteristics. Zone I: continental shelf off western Guangdong Province. Here, the sediment provenance is mainly river-derived from the Pearl River, Taiwanese rivers, and those in the adjacent area. Zone II: Qiongzhou Strait and Leizhou Peninsula. Here, the sediment provenance consists of the Qiongzhou Strait and the Hainan Island. Zone III: Hainan Island and SCS slope sediments are dominated. The REEs compositions are mainly controlled by source rock properties, hydrodynamic conditions, and an intensity of chemical weathering. We reconstructed the sediment dispersal and transport route using the REEs compositions, grain size, and other geochemical characteristics throughout the study area.
Qian Ge; Z. George Xue; Fengyou Chu. Rare Earth Element Distributions in Continental Shelf Sediment, Northern South China Sea. Water 2020, 12, 3540 .
AMA StyleQian Ge, Z. George Xue, Fengyou Chu. Rare Earth Element Distributions in Continental Shelf Sediment, Northern South China Sea. Water. 2020; 12 (12):3540.
Chicago/Turabian StyleQian Ge; Z. George Xue; Fengyou Chu. 2020. "Rare Earth Element Distributions in Continental Shelf Sediment, Northern South China Sea." Water 12, no. 12: 3540.
Rivers and wetlands are a major source of terrestrial derived carbon for coastal ocean margins. This results in a net loss of terrestrial carbon into the shelf water and their subsequent transport to interior ocean basin. This study investigates the transport of Dissolved Inorganic Carbon (DIC) in the surface mixed layer of Louisiana shelf in northern Gulf of Mexico adjacent to the Wax Lake Delta (WLD) and Barataria Bay (BB), which represent contrasting net land gain and net land loss areas in this region. DIC samples were collected, in conjunction with short‐lived radium isotopes 224Ra (t1/2= 3.66 days) and 223Ra (t1/2 = 11.43 days) samples during June and September 2019, to quantify shelf transport of DIC in the surface mixed layer during period of high and low river flow respectively. Radium distribution implied shelf mixing rates of 140‐6759 m2 s‐1 and 63‐2724 m2 s‐1 for WLD and BB regions, respectively, with more than 10‐fold decrease in rates between the two seasons. Net shelf transport of DIC was found to be highest for the WLD region in June, highlighting the importance of freshwater discharge in exporting DIC. An upscaling of our study for the entire Louisiana shelf indicates that 1.54‐20.19 x 109 mol C d‐1 transported in June 2019 and 0.34‐8.12 x x 109 mol C d‐1 in the form of DIC was exported across the shallow region of the shelf during high and low river flow seasons, representing an important source of DIC to the NGOM.
M. M. Anderson; K. Maiti; Z. George Xue; Y. Ou. Dissolved Inorganic Carbon Transport in the Surface‐Mixed Layer of the Louisiana Shelf in Northern Gulf of Mexico. Journal of Geophysical Research: Oceans 2020, 125, 1 .
AMA StyleM. M. Anderson, K. Maiti, Z. George Xue, Y. Ou. Dissolved Inorganic Carbon Transport in the Surface‐Mixed Layer of the Louisiana Shelf in Northern Gulf of Mexico. Journal of Geophysical Research: Oceans. 2020; 125 (11):1.
Chicago/Turabian StyleM. M. Anderson; K. Maiti; Z. George Xue; Y. Ou. 2020. "Dissolved Inorganic Carbon Transport in the Surface‐Mixed Layer of the Louisiana Shelf in Northern Gulf of Mexico." Journal of Geophysical Research: Oceans 125, no. 11: 1.
We introduced a sediment-induced light attenuation algorithm into a biogeochemical model of the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) modeling system. A fully coupled ocean–atmospheric–sediment–biogeochemical simulation was carried out to assess the impact of sediment-induced light attenuation on primary production in the northern Gulf of Mexico during the passage of Hurricane Gustav in 2008. When compared with model results without sediment-induced light attenuation, our new model showed a better agreement with satellite data on both the magnitude of nearshore chlorophyll concentration and the spatial distribution of offshore bloom. When Hurricane Gustav approached, resuspended sediment shifted the inner shelf ecosystem from a nutrient-limited one to a light-limited one. Only 1 week after Hurricane Gustav's landfall, accumulated nutrients and a favorable optical environment induced a posthurricane algal bloom in the top 20 m of the water column, while the productivity in the lower water column was still light-limited due to slow-settling sediment. Corresponding with the elevated offshore NO3 flux (38.71 mmol N m−1 s−1) and decreased chlorophyll flux (43.10 mg m−1 s−1), the outer shelf posthurricane bloom should have resulted from the cross-shelf nutrient supply instead of the lateral dispersed chlorophyll. Sensitivity tests indicated that sediment light attenuation efficiency affected primary production when sediment concentration was moderately high. Model uncertainties due to colored dissolved organic matter and parameterization of sediment-induced light attenuation are also discussed.
Zhengchen Zang; Z. George Xue; Kehui Xu; Samuel J. Bentley; Qin Chen; Eurico J. D'Sa; Le Zhang; Yanda Ou. The role of sediment-induced light attenuation on primary production during Hurricane Gustav (2008). Biogeosciences 2020, 17, 5043 -5055.
AMA StyleZhengchen Zang, Z. George Xue, Kehui Xu, Samuel J. Bentley, Qin Chen, Eurico J. D'Sa, Le Zhang, Yanda Ou. The role of sediment-induced light attenuation on primary production during Hurricane Gustav (2008). Biogeosciences. 2020; 17 (20):5043-5055.
Chicago/Turabian StyleZhengchen Zang; Z. George Xue; Kehui Xu; Samuel J. Bentley; Qin Chen; Eurico J. D'Sa; Le Zhang; Yanda Ou. 2020. "The role of sediment-induced light attenuation on primary production during Hurricane Gustav (2008)." Biogeosciences 17, no. 20: 5043-5055.
A three-dimensional numerical model was applied to the Barataria Estuary in the Northern Gulf of Mexico to study its salinity variations as well as the impacts from the Mississippi River discharges and proposed river diversions. Model-observation comparison showed that the model was able to reproduce the hydrodynamic fields on subtidal to seasonal time scales. Salinity in the Barataria Estuary was high in fall and low in summer, with a greater variability in the lower estuary than the upper estuary. While salinity in the upper estuary was controlled by discharges from a local freshwater diversion, salinity in the lower estuary was mostly affected by the mixed Mississippi River water transported via the tidal inlets in the south. The correlation between Mississippi River discharge and estuarine salinity indicated that low salinity Mississippi River water could intrude into the estuary through the middle and east tidal inlets. Sensitivity tests were performed to assess the impacts from the Mississippi River discharges and proposed mid-Barataria Estuary sediment diversion. Model results illustrated that salinity in the estuary was more sensitive to an increase of Mississippi River discharge than a decrease. The proposed mid-Barataria sediment diversion was likely to induce a dramatic decrease of salinity in the lower estuary. The ecosystem consequences of the fluctuation of Mississippi River discharge as well as that of the proposed river diversions need further investigations.
Yanda Ou; Z. George Xue; Chunyan Li; Kehui Xu; John R. White; Samuel J. Bentley; Zhengchen Zang. A numerical investigation of salinity variations in the Barataria Estuary, Louisiana in connection with the Mississippi River and restoration activities. Estuarine, Coastal and Shelf Science 2020, 245, 107021 .
AMA StyleYanda Ou, Z. George Xue, Chunyan Li, Kehui Xu, John R. White, Samuel J. Bentley, Zhengchen Zang. A numerical investigation of salinity variations in the Barataria Estuary, Louisiana in connection with the Mississippi River and restoration activities. Estuarine, Coastal and Shelf Science. 2020; 245 ():107021.
Chicago/Turabian StyleYanda Ou; Z. George Xue; Chunyan Li; Kehui Xu; John R. White; Samuel J. Bentley; Zhengchen Zang. 2020. "A numerical investigation of salinity variations in the Barataria Estuary, Louisiana in connection with the Mississippi River and restoration activities." Estuarine, Coastal and Shelf Science 245, no. : 107021.
Wave‐supported fluid mud (WSFM) plays an important role in sediment downslope transport on the continental shelves. In this study, we incorporated WSFM processes in the wave boundary layer (WBL) into the Community Sediment Transport Modeling System (CSTMS) on the platform of the Coupled Ocean‐Atmosphere‐Wave‐and‐Sediment Transport modeling system (COAWST). The WSFM module was introduced between the bottommost water layer and top sediment layer, which accounted for the key sediment exchange processes (e.g., resuspension, vertical settling, diffusion, and horizontal advection) at the water‐WBL and WBL‐sediment bed boundaries. To test its robustness, we adapted the updated model (CSTMS+WBL) to the Atchafalaya shelf in the northern Gulf of Mexico, and successfully reproduced the sediment dynamics in March 2008, when active WSFM processes were reported. Compared with original CSTMS results, including WSFM module weakened the overall intensity of sediment resuspension, and the CSTMS+WBL model simulated a lutocline between the WBL and overlying water due to the formation of WSFM. Downslope WSFM transport resulted in offshore deposition (> 4 cm), which greatly changed the net erosion/deposition pattern on the inner shelf off the Chenier Plain. WSFM flux was comparable with suspended sediment flux (SSF) off the Atchafalaya Bay and it peaked along the Chenier Plain coast where wave activities were strong and the bathymetric slope was steep. The influence of fluvial sediment supply on sediment dynamics was limited in the Atchafalaya Bay. Sensitivity tests of free settling, flocculation, and hindered settling effects suggested sediments were transported further offshore due to reduced settling velocity in the WBL once fluid mud was formed. Although sediment concentration in the WBL was sensitive to surface sediment critical shear stress, cohesive bed behavior was less important in WSFM dynamics when compared with strong hydrodynamic during cold fronts.
Zhengchen Zang; Z. George Xue; Kehui Xu; Celalettin E. Ozdemir; Qin Chen; Samuel Bentley; Cihan Sahin. A numerical investigation of wave‐supported gravity flow during cold fronts over the Atchafalaya shelf. Journal of Geophysical Research: Oceans 2020, 125, 1 .
AMA StyleZhengchen Zang, Z. George Xue, Kehui Xu, Celalettin E. Ozdemir, Qin Chen, Samuel Bentley, Cihan Sahin. A numerical investigation of wave‐supported gravity flow during cold fronts over the Atchafalaya shelf. Journal of Geophysical Research: Oceans. 2020; 125 (9):1.
Chicago/Turabian StyleZhengchen Zang; Z. George Xue; Kehui Xu; Celalettin E. Ozdemir; Qin Chen; Samuel Bentley; Cihan Sahin. 2020. "A numerical investigation of wave‐supported gravity flow during cold fronts over the Atchafalaya shelf." Journal of Geophysical Research: Oceans 125, no. 9: 1.
Ship Shoal has been a high-priority target sand resource for dredging activities to restore the eroding barrier islands in Louisiana, USA. The Caminada and Raccoon Island pits were dredged on and near Ship Shoal, which resulted in a mixed texture environment with the redistribution of cohesive mud and noncohesive sand. However, there is very limited knowledge about the source and transport process of suspended muddy sediments near Ship Shoal. The objective of this study is to apply the Regional Ocean Modeling System (ROMS) model to quantify the sediment sources and relative contribution of fluvial sediments with the estuary and shelf sediments delivered to Ship Shoal. The model results showed that suspended mud from the Atchafalaya River can transport and bypass Ship Shoal. Only a minimal amount of suspended mud from the Atchafalaya River can be delivered to Ship Shoal in a one-year time scale. Additionally, suspended mud from the inner shelf could be transported cross Ship Shoal and generate a thin mud layer, which is also considered as the primary sediment source infilling the dredge pits near Ship Shoal. Two hurricanes and one tropical storm during the year 2017–2018 changed the direction of the sediment transport flux near Ship Shoal and contributed to the pit infilling (less than 10% for this specific period). Our model also captured that the bottom sediment concentration in the Raccoon Island pit was relatively higher than the one in Caminada in the same period. Suspended mud sediment from the river, inner shelf, and bay can bypass or transport and deposit in the Caminada pit and Raccoon Island pit, which showed that the Caminada pit and Raccoon Island pits would not be considered as a renewable borrow area for future sand dredging activities for coastal restoration.
Haoran Liu; Kehui Xu; Yanda Ou; Robert Bales; Zhengchen Zang; Z. George Xue. Sediment Transport near Ship Shoal for Coastal Restoration in the Louisiana Shelf: A Model Estimate of the Year 2017–2018. Water 2020, 12, 2212 .
AMA StyleHaoran Liu, Kehui Xu, Yanda Ou, Robert Bales, Zhengchen Zang, Z. George Xue. Sediment Transport near Ship Shoal for Coastal Restoration in the Louisiana Shelf: A Model Estimate of the Year 2017–2018. Water. 2020; 12 (8):2212.
Chicago/Turabian StyleHaoran Liu; Kehui Xu; Yanda Ou; Robert Bales; Zhengchen Zang; Z. George Xue. 2020. "Sediment Transport near Ship Shoal for Coastal Restoration in the Louisiana Shelf: A Model Estimate of the Year 2017–2018." Water 12, no. 8: 2212.
A soil erosion and sediment transport model (WRF-Hydro-Sed) is introduced to WRF-Hydro. As a process-based, fully distributed soil erosion model, WRF-Hydro-Sed accounts for both overland and channel processes. Model performance is evaluated using observed rain gauge, streamflow, and sediment concentration data during rainfall events in the Goodwin Creek Experimental Watershed in Mississippi, USA. Both streamflow and sediment yield can be calibrated and validated successfully at a watershed scale during rainfall events. Further discussion reveals the model’s uncertainty and the applicability of calibrated hydro- and sediment parameters to different events. While an intensive calibration over multiple events can improve the model’s performance to a certain degree compared with single event-based calibration, it might not be an optimal strategy to carry out considering the tremendous computational resources needed.
Dongxiao Yin; Z. George Xue; David J. Gochis; Wei Yu; Mirce Morales; Arezoo Rafieeinasab. A Process-Based, Fully Distributed Soil Erosion and Sediment Transport Model for WRF-Hydro. Water 2020, 12, 1840 .
AMA StyleDongxiao Yin, Z. George Xue, David J. Gochis, Wei Yu, Mirce Morales, Arezoo Rafieeinasab. A Process-Based, Fully Distributed Soil Erosion and Sediment Transport Model for WRF-Hydro. Water. 2020; 12 (6):1840.
Chicago/Turabian StyleDongxiao Yin; Z. George Xue; David J. Gochis; Wei Yu; Mirce Morales; Arezoo Rafieeinasab. 2020. "A Process-Based, Fully Distributed Soil Erosion and Sediment Transport Model for WRF-Hydro." Water 12, no. 6: 1840.
Coastal Louisiana hosts 37% of the coastal wetland area in the conterminous US, including one of the deltaic coastal regions more susceptible to the synergy of human and natural impacts causing wetland loss. As a result of the construction of flood protection infrastructure, dredging of channels across wetlands for oil/gas exploration and maritime transport activities, coastal Louisiana has lost approximately 4900 km2 of wetland area since the early 1930s. Despite the economic relevance of both wetland biomass and net primary productivity (NPP) as ecosystem services, there is a lack of vegetation simulation models to forecast the trends of those functional attributes at the landscape level as hydrological restoration projects are implemented. Here, we review the availability of peer-reviewed biomass and NPP wetland data (below and aboveground) published during the period 1976–2015 for use in the development, calibration and validation of high spatial resolution (
Victor H. Rivera-Monroy; Courtney Elliton; Siddhartha Narra; Ehab Meselhe; Xiaochen Zhao; Eric White; Charles E. Sasser; Jenneke M. Visser; Xuelian Meng; Hongqing Wang; Zuo Xue; Fernando Jaramillo; Rivera- Monroy; Zhao; Meng; Wang; Xue. Wetland Biomass and Productivity in Coastal Louisiana: Base Line Data (1976–2015) and Knowledge Gaps for the Development of Spatially Explicit Models for Ecosystem Restoration and Rehabilitation Initiatives. Water 2019, 11, 2054 .
AMA StyleVictor H. Rivera-Monroy, Courtney Elliton, Siddhartha Narra, Ehab Meselhe, Xiaochen Zhao, Eric White, Charles E. Sasser, Jenneke M. Visser, Xuelian Meng, Hongqing Wang, Zuo Xue, Fernando Jaramillo, Rivera- Monroy, Zhao, Meng, Wang, Xue. Wetland Biomass and Productivity in Coastal Louisiana: Base Line Data (1976–2015) and Knowledge Gaps for the Development of Spatially Explicit Models for Ecosystem Restoration and Rehabilitation Initiatives. Water. 2019; 11 (10):2054.
Chicago/Turabian StyleVictor H. Rivera-Monroy; Courtney Elliton; Siddhartha Narra; Ehab Meselhe; Xiaochen Zhao; Eric White; Charles E. Sasser; Jenneke M. Visser; Xuelian Meng; Hongqing Wang; Zuo Xue; Fernando Jaramillo; Rivera- Monroy; Zhao; Meng; Wang; Xue. 2019. "Wetland Biomass and Productivity in Coastal Louisiana: Base Line Data (1976–2015) and Knowledge Gaps for the Development of Spatially Explicit Models for Ecosystem Restoration and Rehabilitation Initiatives." Water 11, no. 10: 2054.
We adapted the coupled ocean-sediment transport model to the northern Gulf of Mexico to examine sediment dynamics on seasonal-to-decadal time scales as well as its response to decreased fluvial inputs from the Mississippi-Atchafalaya River. Sediment transport on the shelf exhibited contrasting conditions in a year, with strong westward transport in spring, fall, and winter, and relatively weak eastward transport in summer. Sedimentation rate varied from almost zero on the open shelf to more than 10 cm/year near river mouths. A phase shift in river discharge was detected in 1999 and was associated with the El Niño-Southern Oscillation (ENSO) event, after which, water and sediment fluxes decreased by ~20% and ~40%, respectively. Two sensitivity tests were carried out to examine the response of sediment dynamics to high and low river discharge, respectively. With a decreased fluvial supply, sediment flux and sedimentation rate were largely reduced in areas proximal to the deltas, which might accelerate the land loss in down-coast bays and estuaries. The results of two sensitivity tests indicated the decreased river discharge would largely affect sediment balance in waters around the delta. The impact from decreased fluvial input was minimum on the sandy shoals ~100 km west of the Mississippi Delta, where deposition of fluvial sediments was highly affected by winds.
Zhengchen Zang; Z. George Xue; Kehui Xu; Samuel J. Bentley; Qin Chen; Eurico J. D’Sa; Qian Ge. A Two Decadal (1993–2012) Numerical Assessment of Sediment Dynamics in the Northern Gulf of Mexico. Water 2019, 11, 938 .
AMA StyleZhengchen Zang, Z. George Xue, Kehui Xu, Samuel J. Bentley, Qin Chen, Eurico J. D’Sa, Qian Ge. A Two Decadal (1993–2012) Numerical Assessment of Sediment Dynamics in the Northern Gulf of Mexico. Water. 2019; 11 (5):938.
Chicago/Turabian StyleZhengchen Zang; Z. George Xue; Kehui Xu; Samuel J. Bentley; Qin Chen; Eurico J. D’Sa; Qian Ge. 2019. "A Two Decadal (1993–2012) Numerical Assessment of Sediment Dynamics in the Northern Gulf of Mexico." Water 11, no. 5: 938.
Surface sediments collected from the continental shelf off the western Guangdong Province and northeastern Hainan Island are analyzed for selected heavy metals contents including Cd, Cr, Cu, Pb, Zn, and As to determine spatial distribution, potential ecological risks, and sources. In addition, some of the controlling factors of heavy metals distribution are also discussed. The average heavy metals contents decrease in the order of Zn > Cr > Pb > Cu > As > Cd. The averaged pollution degree, as shown by the index of geo-accumulation (Igeo), decreases in the order of Zn > Cu > Pb > Cr > Cd > As. Due to the barrier of islands, the Igeo values of Zn, Pb, Cr, Cu, and Cd near the Hailing and Xiachuan Islands are larger than those in other areas. Meanwhile, the Igeo value of As near the coastal area off the estuary of Wanquan River is clearly larger than that in other areas. Based on the results of potential ecological risk index, Cd, Cu, and As should be paid more attention for the contamination risk in future. The results of Pearson correlation analysis and principal component analysis indicate that Zn, Cr, Pb, Cu, and Cd are mainly from the Pearl River and surrounding small rivers, whereas As originates from the Hainan Island. The grain size is one of the main controlling factors for heavy metals distribution, and the anthropogenic activity also plays an important role.
Qian Ge; Zuo George Xue; Fengyou Chu. Spatial Distribution and Contamination Assessment of Surface Heavy Metals off the Western Guangdong Province and Northeastern Hainan Island. International Journal of Environmental Research and Public Health 2018, 15, 1897 .
AMA StyleQian Ge, Zuo George Xue, Fengyou Chu. Spatial Distribution and Contamination Assessment of Surface Heavy Metals off the Western Guangdong Province and Northeastern Hainan Island. International Journal of Environmental Research and Public Health. 2018; 15 (9):1897.
Chicago/Turabian StyleQian Ge; Zuo George Xue; Fengyou Chu. 2018. "Spatial Distribution and Contamination Assessment of Surface Heavy Metals off the Western Guangdong Province and Northeastern Hainan Island." International Journal of Environmental Research and Public Health 15, no. 9: 1897.
Zhengchen Zang; Z. George Xue; Shaowu Bao; Qin Chen; Nan D. Walker; Alaric S. Haag; Qian Ge; Zhigang Yao. Numerical study of sediment dynamics during hurricane Gustav. Ocean Modelling 2018, 126, 29 -42.
AMA StyleZhengchen Zang, Z. George Xue, Shaowu Bao, Qin Chen, Nan D. Walker, Alaric S. Haag, Qian Ge, Zhigang Yao. Numerical study of sediment dynamics during hurricane Gustav. Ocean Modelling. 2018; 126 ():29-42.
Chicago/Turabian StyleZhengchen Zang; Z. George Xue; Shaowu Bao; Qin Chen; Nan D. Walker; Alaric S. Haag; Qian Ge; Zhigang Yao. 2018. "Numerical study of sediment dynamics during hurricane Gustav." Ocean Modelling 126, no. : 29-42.
We applied the newly developed WRF-Hydro model to investigate the hydroclimatic trend encompassing the three basins in Southwest Louisiana as well as their connection with large-scale atmospheric drivers. Using the North American Land Data Assimilation System Phase 2 (NLDAS-2), we performed a multi-decadal model hindcast covering the period of 1979–2014. After validating the model’s performance against available observations, trend and wavelet analysis were applied on the time series of hydroclimatic variables from NLDAS-2 (temperature and precipitation) and model results (evapotranspiration, soil moisture, water surplus, and streamflow). Trend analysis of model-simulated monthly and annual time series indicates that the regional climate is warming and drying over the past decades, specifically during spring and summer (growing season). Wavelet analysis reveals that, since the late 1990s, the anomaly of evapotranspiration, soil moisture, and streamflow exhibits high coherency with that of precipitation. Pettitt’s test detects a possible change-point around the year 2004, after which the monthly precipitation decreased from 140 to 120 mm, evapotranspiration slightly increased from 80 to 83 mm, and water surplus decreased from 60 to 38 mm. Changes in regional climate conditions are closely correlated with large-scale climate dynamics such as the Atlantic Multidecadal Oscillation (AMO) and El Niño Southern Oscillation (ENSO).
Z. George Xue; David J. Gochis; Wei Yu; Barry D. Keim; Robert V. Rohli; Zhengchen Zang; Kevin Sampson; Aubrey Dugger; David Sathiaraj; Qian Ge. Modeling Hydroclimatic Change in Southwest Louisiana Rivers. Water 2018, 10, 596 .
AMA StyleZ. George Xue, David J. Gochis, Wei Yu, Barry D. Keim, Robert V. Rohli, Zhengchen Zang, Kevin Sampson, Aubrey Dugger, David Sathiaraj, Qian Ge. Modeling Hydroclimatic Change in Southwest Louisiana Rivers. Water. 2018; 10 (5):596.
Chicago/Turabian StyleZ. George Xue; David J. Gochis; Wei Yu; Barry D. Keim; Robert V. Rohli; Zhengchen Zang; Kevin Sampson; Aubrey Dugger; David Sathiaraj; Qian Ge. 2018. "Modeling Hydroclimatic Change in Southwest Louisiana Rivers." Water 10, no. 5: 596.
Satellite approaches for estimation of the partial pressure of CO2 (pCO2) and air-sea flux of CO2 in coastal regions offer the potential to reduce uncertainties in coastal carbon budgets and improve understanding of spatial and temporal patterns and the factors influencing them. We used satellite-derived products in combination with an extensive data set of ship-based observations to develop an unprecedented multi-year time-series of pCO2 and air-sea flux of CO2 in the northern Gulf of Mexico for the period 2006–2010. A regression tree algorithm was used to relate satellite-derived products for chlorophyll, sea surface temperature, and dissolved and detrital organic matter to ship observations of pCO2. The resulting relationship had an r2 of 0.827 and a prediction error of 31.7 μatm pCO2 (root mean-squared error of the relationship was 28.8 μatm). Using a wind speed and gas exchange relationship along with satellite winds, estimates of air-sea flux of CO2 were derived yielding an average annual flux over the period 2006–2010 of − 0.8 to − 1.5 (annual mean = − 1.1 ± 0.3) mol C m− 2 y− 1, where the negative value indicates net ocean uptake. The estimated total annual CO2 flux for the study region was − 4.3 + 1.1 Tg C y− 1. Relationships of satellite-derived pCO2 with salinity were consistent with shipboard observations and exhibited a concave relationship with low values at mid- and low salinities attributed to strong biological drawdown of CO2 in the high productivity river-mixing zone. The time-series of satellite-derived pCO2 was characterized by a seasonal pattern with values lower during winter and spring, low to intermediate values during fall, and higher and more variable values during summer. These findings were similar to simulations from a coupled physical-biogeochemical model. A seasonal pattern was also evident in the air-sea flux of CO2 with generally more negative fluxes (i.e., ocean uptake) during winter and spring, and positive fluxes during summer months with fall being a period of transition. Interannual variations in annual means of both air-sea flux of CO2 and DIN loading were significant, with higher DIN loading coinciding in some cases with more negative air-sea flux of CO2 (i.e., net ocean uptake). Spatial patterns of pCO2 reflected regional environmental forcing including effects of river discharge, wind forcing, and shelf-slope circulation. Our study also illustrates the utility of satellite extrapolation for highlighting areas that may contribute significantly to regional signals and for guiding prioritization of locations for acquiring further observations. The approach should be readily applicable to other regions given adequate availability of in situ observations for algorithm development.
S.E. Lohrenz; W.-J. Cai; S. Chakraborty; W.-J. Huang; X. Guo; R. He; Z. Xue; K. Fennel; S. Howden; H. Tian. Satellite estimation of coastal pCO2 and air-sea flux of carbon dioxide in the northern Gulf of Mexico. Remote Sensing of Environment 2018, 207, 71 -83.
AMA StyleS.E. Lohrenz, W.-J. Cai, S. Chakraborty, W.-J. Huang, X. Guo, R. He, Z. Xue, K. Fennel, S. Howden, H. Tian. Satellite estimation of coastal pCO2 and air-sea flux of carbon dioxide in the northern Gulf of Mexico. Remote Sensing of Environment. 2018; 207 ():71-83.
Chicago/Turabian StyleS.E. Lohrenz; W.-J. Cai; S. Chakraborty; W.-J. Huang; X. Guo; R. He; Z. Xue; K. Fennel; S. Howden; H. Tian. 2018. "Satellite estimation of coastal pCO2 and air-sea flux of carbon dioxide in the northern Gulf of Mexico." Remote Sensing of Environment 207, no. : 71-83.
A three-dimensional coupled physical–biogeochemical model was used to simulate and examine temporal and spatial variability of sea surface pCO2 in the Gulf of Mexico (GoM). The model was driven by realistic atmospheric forcing, open boundary conditions from a data-assimilative global ocean circulation model, and observed freshwater and terrestrial nutrient and carbon input from major rivers. A 7-year model hindcast (2004–2010) was performed and validated against ship measurements. Model results revealed clear seasonality in surface pCO2 and were used to estimate carbon budgets in the Gulf. Based on the average of model simulations, the GoM was a net CO2 sink with a flux of 1.11 ± 0.84 × 1012 mol C yr−1, which, together with the enormous fluvial inorganic carbon input, was comparable to the inorganic carbon export through the Loop Current. Two model sensitivity experiments were performed: one without biological sources and sinks and the other using river input from the 1904–1910 period as simulated by the Dynamic Land Ecosystem Model (DLEM). It was found that biological uptake was the primary driver making GoM an overall CO2 sink and that the carbon flux in the northern GoM was very susceptible to changes in river forcing. Large uncertainties in model simulations warrant further process-based investigations.
Zuo Xue; Ruoying He; Katja Fennel; Wei- Jun Cai; Steven Lohrenz; Wei- Jen Huang; Hanqin Tian; Wei Ren; Zhengchen Zang. Modeling pCO2 variability in the Gulf of Mexico. Biogeosciences 2016, 13, 4359 -4377.
AMA StyleZuo Xue, Ruoying He, Katja Fennel, Wei- Jun Cai, Steven Lohrenz, Wei- Jen Huang, Hanqin Tian, Wei Ren, Zhengchen Zang. Modeling pCO2 variability in the Gulf of Mexico. Biogeosciences. 2016; 13 (15):4359-4377.
Chicago/Turabian StyleZuo Xue; Ruoying He; Katja Fennel; Wei- Jun Cai; Steven Lohrenz; Wei- Jen Huang; Hanqin Tian; Wei Ren; Zhengchen Zang. 2016. "Modeling pCO2 variability in the Gulf of Mexico." Biogeosciences 13, no. 15: 4359-4377.