scholarly journals Hurricane Arthur and its effect on the short-term variability of pCO<sub>2</sub> on the Scotian Shelf, NW Atlantic

2017 ◽  
Author(s):  
Jonathan Lemay ◽  
Helmuth Thomas ◽  
Susanne E. Craig ◽  
William J. Burt ◽  
Katja Fennel ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Carbon Cycling ◽  
Dissolved Inorganic Carbon ◽  
High Temporal Resolution ◽  
Co2 Uptake ◽  
Surface Mixed Layer ◽  
Scotian Shelf ◽  
Short Term ◽  
Partial Pressure Of Co2 ◽  
Short Term Variability

Abstract. The understanding of seasonal variability of carbon cycling on the Scotian Shelf, NW Atlantic Ocean, has improved in recent years, however, very little information is available regarding its short-term variability. In order to shed light on this aspect of carbon cycling on the Scotian Shelf we investigate the effects of Hurricane Arthur, which passed the region on July 5th 2014. The hurricane caused a substantial decline in the surface water partial pressure of CO2 (pCO2), even though the Scotian Shelf possesses CO2 rich deep waters. High temporal resolution data of moored autonomous instruments demonstrate that there is a distinct layer of relatively cold water with low dissolved inorganic carbon (DIC) slightly above the thermocline, presumably due to a sustained population of phytoplankton. Strong storm-related wind mixing caused this cold intermediate layer with high phytoplankton biomass to be entrained into the surface mixed layer. At the surface, phytoplankton begin to grow more rapidly due to increased light. The combination of growth and mixing of low DIC water led to a short-term reduction in partial pressure of CO2 until wind speeds relaxed and allowed for the restratification of the upper water column. These Hurricane-related processes caused a (net-) CO2 uptake by the Scotian Shelf region that is comparable to the spring bloom, thus exerting a major impact on the annual CO2 flux budget.

scholarly journals Hurricane Arthur and its effect on the short-term variability of <i>p</i>CO<sub>2</sub> on the Scotian Shelf, NW Atlantic

2018 ◽  
Vol 15 (7) ◽  
pp. 2111-2123 ◽  
Author(s):  
Jonathan Lemay ◽  
Helmuth Thomas ◽  
Susanne E. Craig ◽  
William J. Burt ◽  
Katja Fennel ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Carbon Cycling ◽  
Dissolved Inorganic Carbon ◽  
High Temporal Resolution ◽  
Co2 Uptake ◽  
Surface Mixed Layer ◽  
Scotian Shelf ◽  
Short Term ◽  
Partial Pressure Of Co2 ◽  
Short Term Variability

Abstract. The understanding of the seasonal variability of carbon cycling on the Scotian Shelf in the NW Atlantic Ocean has improved in recent years; however, very little information is available regarding its short-term variability. In order to shed light on this aspect of carbon cycling on the Scotian Shelf we investigate the effects of Hurricane Arthur, which passed the region on 5 July 2014. The hurricane caused a substantial decline in the surface water partial pressure of CO2 (pCO2), even though the Scotian Shelf possesses CO2-rich deep waters. High-temporal-resolution data of moored autonomous instruments demonstrate that there is a distinct layer of relatively cold water with low dissolved inorganic carbon (DIC) slightly above the thermocline, presumably due to a sustained population of phytoplankton. Strong storm-related wind mixing caused this cold intermediate layer with high phytoplankton biomass to be entrained into the surface mixed layer. At the surface, phytoplankton begin to grow more rapidly due to increased light. The combination of growth and the mixing of low DIC water led to a short-term reduction in the partial pressure of CO2 until wind speeds relaxed and allowed for the restratification of the upper water column. These hurricane-related processes caused a (net) CO2 uptake by the Scotian Shelf region that is comparable to the spring bloom, thus exerting a major impact on the annual CO2 flux budget.

scholarly journals Spatio-temporal variability of the CO<sub>2</sub> system on the Scotian Shelf

2011 ◽  
Vol 8 (6) ◽  
pp. 12013-12050 ◽  
Author(s):  
E. H. Shadwick ◽  
H. Thomas ◽  
A. E. F. Prowe ◽  
E. Horne
Keyword(s):  
Temporal Variability ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Large Fraction ◽  
Monitoring Program ◽  
Total Alkalinity ◽  
Surface Mixed Layer ◽  
Scotian Shelf ◽  
Lawrence Estuary ◽  
Spatio Temporal

Abstract. Relative to their surface areas, coastal oceans and continental shelves host a disproportionately large fraction of ocean productivity. The Scotian Shelf is a biologically productive coastal region of the Northwestern Atlantic Ocean. This subpolar region is influenced by the outflow of the St. Lawrence Estuary system and acts as an annual source for atmospheric CO2. As part of the Atlantic Zone Monitoring Program, dissolved inorganic carbon (DIC), total alkalinity, and surface CO2 partial pressure measurements were made throughout the Scotian Shelf in 2007. A shelf-wide assessment of the spatio-temporal variability of the inorganic carbon system was made relying on observations in April and September. Between these periods, biological production results in a significant drawdown of inorganic nutrients and DIC in the surface mixed-layer, while hydrographic controls also influence seasonal changes in DIC. Net community production (NCP) over the spring and summer seasons was estimated on the basis of inorganic carbon data. We find significant spatial variability in NCP with the largest values in the Southwestern Browns Bank region and a general trend of increasing NCP with distance offshore. A bulk seasonal carbon budget suggests that along-shore and cross-shelf transport may result in the export of subsurface DIC from this region.

scholarly journals Shallow plant-dominated lakes – extreme environmental variability, carbon cycling and ecological species challenges

2019 ◽  
Vol 124 (3) ◽  
pp. 355-366 ◽  
Author(s):  
Kaj Sand-Jensen ◽  
Mikkel René Andersen ◽  
Kenneth Thorø Martinsen ◽  
Jens Borum ◽  
Emil Kristensen ◽  
...  
Keyword(s):  
Carbon Cycling ◽  
Surface Waters ◽  
Shallow Lakes ◽  
Environmental Variability ◽  
Dissolved Inorganic Carbon ◽  
Plant Distribution ◽  
High Temporal Resolution ◽  
Surface Cooling ◽  
Dense Vegetation ◽  
Bottom Waters

Abstract Background Submerged plants composed of charophytes (green algae) and angiosperms develop dense vegetation in small, shallow lakes and in littoral zones of large lakes. Many small, oligotrophic plant species have declined due to drainage and fertilization of lakes, while some tall, eutrophic species have increased. Although plant distribution has been thoroughly studied, the physiochemical dynamics and biological challenges in plant-dominated lakes have been grossly understudied, even though they may offer the key to species persistence. Scope Small plant-dominated lakes function as natural field laboratories with eco-physiological processes in dense vegetation dictating extreme environmental variability, intensive photosynthesis and carbon cycling. Those processes can be quantified on a whole lake basis at high temporal resolution by continuously operating sensors for light, temperature, oxygen, etc. We explore this hitherto hidden world. Conclusions Dense plant canopies attenuate light and wind-driven turbulence and generate separation between warm surface water and colder bottom waters. Daytime vertical stratification becomes particularly strong in dense charophyte vegetation, but stratification is a common feature in small, shallow lakes also without plants. Surface cooling at night induces mixing of the water column. Daytime stratification in plant stands may induce hypoxia or anoxia in dark bottom waters by respiration, while surface waters develop oxygen supersaturation by photosynthesis. Intensive photosynthesis and calcification in shallow charophyte lakes depletes dissolved inorganic carbon (DIC) in surface waters, whereas DIC is replenished by respiration and carbonate dissolution in bottom waters and returned to surface waters before sunrise. Extreme diel changes in temperature, DIC and oxygen in dense vegetation can induce extensive rhythmicity of photosynthesis and respiration and become a severe challenge to the survival of organisms. Large phosphorus pools are bound in plant tissue and carbonate precipitates. Future studies should test the importance of this phosphorus sink for ecosystem processes and competition between phytoplankton and plants.

scholarly journals Daily CO<sub>2</sub> partial pressure and CO<sub>2</sub> outgassing in the upper Yangtze River basin: a case study of Longchuanjiang, China

2011 ◽  
Vol 8 (5) ◽  
pp. 10645-10676 ◽  
Author(s):  
S. Y. Li ◽  
X. X. Lu ◽  
M. He ◽  
Y. Zhou ◽  
L. Li ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Temporal Resolution ◽  
Dissolved Inorganic Carbon ◽  
Anthropogenic Activities ◽  
Yangtze River Basin ◽  
Water Discharge ◽  
Biogenic Elements ◽  
High Temporal Resolution ◽  
Survey Period ◽  
Co2 Degassing

Abstract. Rivers have been under sampled to establish them as sinks or sources of the atmospheric carbon oxide (CO2). Such poor coverage is well known for tropical and sub-tropical, particularly monsoon driven rivers. An unprecedented high-temporal-resolution (daily) sampling during July 2008–August 2009 were conducted from the Longchuanjiang River of the upper Yangtze basin, a subtropical monsoon river in China to reveal the daily-to-seasonal dynamics of the partial pressure of CO2 (pCO2) and CO2 degassing flux from the river. The pCO2 levels were supersaturated in CO2 with respect to atmospheric equilibrium (380 μatm) during the entire survey period with obvious daily and seasonal variations, ranging from 450 to 63 000 μatm with an average of 3900 μatm. pCO2 values in the surface water in the wet season were relatively low, except flooding period in November, due to a dilution effect by heavy rainfall. However, both daily and monthly minimal and maximal pCO2 also occurred in this period. In contrast, the pCO2 levels in the dry season were much higher, mainly resulted from lower pH by anthropogenic activities. Net CO2 flux and pCO2 were strongly correlated with pH, but weakly with water temperature, dissolved inorganic carbon and water discharge, and uncorrelated with particulate nutrients and biogenic elements. The estimated water-to-air CO2 degassing flux in the Longchuanjiang River was about 110 mol m−2 yr−1, with the upper limit of 460 mol m−2 yr−1. Our study also indicated that among the total organic carbon remobilized through soil erosion, around 17% (11 400 t C yr−1) of was emitted to the atmosphere, 52% (35 000 t C yr−1) deposited in the river-reservoirs system and 31% (21 000 t C yr−1) exported further downstream. High spatial and temporal resolution of estimates of CO2 emission from the world large rivers is required due to that catchment characteristics and anthropogenic activities are extremely heterogeneous in space and time.

scholarly journals Partial pressure of CO<sub>2</sub> and CO<sub>2</sub> emission in a monsoon-driven hydroelectric reservoir (Danjiangkou Reservoir), China

2013 ◽  
Vol 10 (6) ◽  
pp. 10055-10094
Author(s):  
S. Y. Li ◽  
Q. F. Zhang
Keyword(s):  
Partial Pressure ◽  
Dissolved Inorganic Carbon ◽  
Co2 Flux ◽  
Total Alkalinity ◽  
Biogenic Elements ◽  
Co2 Uptake ◽  
Danjiangkou Reservoir ◽  
Chl A ◽  
Hydroelectric Reservoirs ◽  
Hydroelectric Reservoir

Abstract. Hydroelectric reservoirs have been under sampled to establish them as sources or sinks of the atmospheric carbon dioxide (CO2). Such poor coverage is well known for subtropic, particularly monsoon driven reservoirs in China. Our study presented the spatiotemporal changes of the carbonate system and CO2 flux in a hydroelectric reservoir (Dangjiankou Reservoir) locating in a subtropical monsoon climate region. Our 21 filed surveys conducted during 2004–2011 revealed significantly spatial and monthly variations of surface water partial pressure of CO2 (pCO2) in the Reservoir. pCO2, showing higher concentrations in the wet and warm seasons, averaged 595 ± 545 µatm (ranging from 53–3751 µatm) in the reservoir surface, while substantially higher pCO2 (1132 ± 1220 µatm) was observed in the river downstream the dam. A clear pCO2 drawdown in the reservoir as water flows demonstrated a significantly descending order of Dan Reservoir > site close to dam > Han Reservoir. This spatial contrast can also be seen in the distributions of dissolved inorganic carbon and total alkalinity. Pronounced seasonality in pCO2 was controlled by seasonal monsoon rainfall, while photosynthetic CO2 uptake dominated spatial patterns and dry-month variability of pCO2. We further related pCO2 to water chemical properties and indicated that pCO2 had strong positive correlations with Si, TP and DOC, negative correlations with DO saturation, TN and Chl a, while weak correlations with other variables including biogenic elements. CO2 flux from the Reservoir surface showed a bottom average of 9 mmol m–2 d–2 in comparison with other hydroelectric reservoir in China. River downstream the dam had quite high flux of CO2 (119 mmol m–2 d–2), which was intermediate between temperate rivers and compared to global rivers' average. This means that water releasing from reservoir would be an important channel for atmospheric CO2 sources. The annual CO2 emission from the Danjiangkou Reservoir was estimated to be 3.4 × 109 mol C. Remarkably spatial and temporal heterogeneities in CO2 flux from China's hydroelectric reservoirs are urgently included for advancing global models of reservoirs' carbon emissions.

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