scholarly journals Air-Sea CO<sub>2</sub> fluxes on the Scotian Shelf: seasonal to multi-annual variability

2010 ◽  
Vol 7 (11) ◽  
pp. 3851-3867 ◽  
Author(s):  
E. H. Shadwick ◽  
H. Thomas ◽  
A. Comeau ◽  
S. E. Craig ◽  
C. W. Hunt ◽  
...  
Keyword(s):  
Time Series ◽  
Surface Waters ◽  
Gulf Of Maine ◽  
Co2 Flux ◽  
Sea Surface ◽  
Co2 Fluxes ◽  
Resolution Time ◽  
Scotian Shelf ◽  
Shelf Region ◽  
Annual Scale

Abstract. We develop an algorithm to compute pCO2 in the Scotian Shelf region (NW Atlantic) from satellite-based estimates of chlorophyll-a concentration, sea-surface temperature, and observed wind speed. This algorithm is based on a high-resolution time-series of pCO2 observations from an autonomous mooring. At the mooring location (44.3° N and 63.3° W), the surface waters act as a source of CO2 to the atmosphere over the annual scale, with an outgassing of −1.1 mol C m−2 yr−1 in 2007/2008. A hindcast of air-sea CO2 fluxes from 1999 to 2008 reveals significant variability both spatially and from year to year. Over the decade, the shelf-wide annual air-sea fluxes range from an outgassing of −1.70 mol C m−2 yr−1 in 2002, to −0.02 mol C m−2 yr−1 in 2006. There is a gradient in the air-sea CO2 flux between the northeastern Cabot Strait region which acts as a net sink of CO2 with an annual uptake of 0.50 to 1.00 mol C m−2 yr−1, and the southwestern Gulf of Maine region which acts as a source ranging from −0.80 to −2.50 mol C m−2 yr−1. There is a decline, or a negative trend, in the air-sea pCO2 gradient of 23 μatm over the decade, which can be explained by a cooling of 1.3 °C over the same period. Regional conditions govern spatial, seasonal, and interannual variability on the Scotian Shelf, while multi-annual trends appear to be influenced by larger scale processes.

scholarly journals Satellite observations reveal high variability and a decreasing trend in CO<sub>2</sub> fluxes on the Scotian Shelf

2010 ◽  
Vol 7 (4) ◽  
pp. 5269-5304
Author(s):  
E. H. Shadwick ◽  
H. Thomas ◽  
A. Comeau ◽  
S. E. Craig ◽  
C. W. Hunt ◽  
...  
Keyword(s):  
North Atlantic ◽  
Surface Waters ◽  
Gulf Of Maine ◽  
Co2 Flux ◽  
Resolution Time ◽  
Scotian Shelf ◽  
The North ◽  
The North Atlantic Oscillation ◽  
Shelf Region ◽  
Annual Scale

Abstract. We develop an algorithm to compute pCO2 in the Scotian Shelf region (NW Atlantic) from satellite-based estimates of chlorophyll-a concentration, sea-surface temperature, and observed wind speed. This algorithm is based on a high-resolution time-series of pCO2 observations from an autonomous mooring. At the mooring location (44.3° N and 63.3° W), the surface waters act as a source of CO2 to the atmosphere over the annual scale, with an outgassing of −1.1 mol C m−2 yr−1 in 2007/2008. A hindcast of air-sea CO2 fluxes from 1999 to 2008 reveals significant variability both spatially and from year to year. Over the decade, the shelf-wide annual air-sea fluxes range from an outgassing of −1.7 mol C m−2 yr−1 in 2002, to −0.02 mol C m−2 yr−1 in 2006. There is a gradient in the air-sea CO2 flux between the northeastern Cabot Strait region which acts as a net sink of CO2 with an annual uptake of 0.5 to 1.0 mol C m−2 yr−1, and the southwestern Gulf of Maine region which acts as a source ranging from −0.8 to −2.5 mol C m−2 yr−1. There is a decline, or a negative trend, in the air-sea pCO2 gradient of 23 μatm over the decade, which can be explained by a cooling of 1.3 °C over the same period. Regional conditions govern spatial, seasonal, and interannual variability on the Scotian Shelf, while multi-annual trends appear linked to the North Atlantic Oscillation.

scholarly journals Seasonal trends and phenology shifts in sea surface temperature on the North American northeastern continental shelf

Elem Sci Anth ◽  
2017 ◽  
Vol 5 ◽  
Author(s):  
Andrew C. Thomas ◽  
Andrew J. Pershing ◽  
Kevin D. Friedland ◽  
Janet A. Nye ◽  
Katherine E. Mills ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Continental Shelf ◽  
Sea Surface Temperature ◽  
North American ◽  
Gulf Of Maine ◽  
Sea Surface ◽  
Scotian Shelf ◽  
Seasonal Differences ◽  
Study Region ◽  
The North

The northeastern North American continental shelf from Cape Hatteras to the Scotian Shelf is a region of globally extreme positive trends in sea surface temperature (SST). Here, a 33-year (1982–2014) time series of daily satellite SST data was used to quantify and map spatial patterns in SST trends and phenology over this shelf. Strongest trends are over the Scotian Shelf (&gt;0.6°C decade–1) and Gulf of Maine (&gt;0.4°C decade–1) with weaker trends over the inner Mid-Atlantic Bight (~0.3°C decade–1). Winter (January–April) trends are relatively weak, and even negative in some areas; early summer (May–June) trends are positive everywhere, and later summer (July–September) trends are strongest (~1.0°C decade–1). These seasonal differences shift the phenology of many metrics of the SST cycle. The yearday on which specific temperature thresholds (8° and 12°C) are reached in spring trends earlier, most strongly over the Scotian Shelf and Gulf of Maine (~ –0.5 days year–1). Three metrics defining the warmest summer period show significant trends towards earlier summer starts, later summer ends and longer summer duration over the entire study region. Trends in start and end dates are strongest (~1 day year–1) over the Gulf of Maine and Scotian Shelf. Trends in increased summer duration are &gt;2.0 days year–1 in parts of the Gulf of Maine. Regression analyses show that phenology trends have regionally varying links to the North Atlantic Oscillation, to local spring and summer atmospheric pressure and air temperature and to Gulf Stream position. For effective monitoring and management of dynamically heterogeneous shelf regions, the results highlight the need to quantify spatial and seasonal differences in SST trends as well as trends in SST phenology, each of which likely has implications for the ecological functioning of the shelf.

scholarly journals Interaction between the Tidal and Seasonal Variability of the Gulf of Maine and Scotian Shelf Region

2016 ◽  
Vol 46 (11) ◽  
pp. 3279-3298 ◽  
Author(s):  
Anna Katavouta ◽  
Keith R. Thompson ◽  
Youyu Lu ◽  
John W. Loder
Keyword(s):  
Gulf Of Maine ◽  
Circulation Model ◽  
Surface Current ◽  
Maximum Speed ◽  
Georges Bank ◽  
Scotian Shelf ◽  
Linear Superposition ◽  
Dynamical Interaction ◽  
The North ◽  
Shelf Region

AbstractAs part of a broader study of ocean downscaling, the seasonal and tidal variability of the Gulf of Maine and Scotian shelf, and their dynamical interaction, are investigated using a high-resolution (1/36°) circulation model. The model’s seasonal hydrography and circulation, and its tidal elevations and currents, are compared with an observed seasonal climatology, local observations, and results from previous studies. Numerical experiments with and without density stratification demonstrate the influence of stratification on the tides. The model is then used to interpret the physical mechanisms responsible for the largest seasonal variations in the M2 surface current that occur over, and to the north of, Georges Bank. The model generates a striation pattern of alternating highs and lows, aligned with Georges Bank, in the M2 surface summer maximum speed in the Gulf of Maine. The striations are consistent with observations by a high-frequency coastal radar system and can be explained in terms of a linear superposition of the barotropic tide and the first-mode baroclinic tide, generated on the north side of Georges Bank, as it propagates into the Gulf of Maine. The seasonal changes in tidal currents in the well-mixed area on Georges Bank are due to a combination of increased sea level gradients, and lower vertical viscosity, in summer.

scholarly journals Seasonal variations of sea–air CO<sub>2</sub> fluxes in the largest tropical marginal sea (South China Sea) based on multiple-year underway measurements

2013 ◽  
Vol 10 (11) ◽  
pp. 7775-7791 ◽  
Author(s):  
W.-D. Zhai ◽  
M.-H. Dai ◽  
B.-S. Chen ◽  
X.-H. Guo ◽  
Q. Li ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
River Estuary ◽  
Co2 Flux ◽  
Pearl River Estuary ◽  
Sea Surface ◽  
Atmospheric Co2 ◽  
Pearl River ◽  
Co2 Fluxes ◽  
The Pearl River

Abstract. Based upon 14 field surveys conducted between 2003 and 2008, we showed that the seasonal pattern of sea surface partial pressure of CO2 (pCO2) and sea–air CO2 fluxes differed among four different physical–biogeochemical domains in the South China Sea (SCS) proper. The four domains were located between 7 and 23° N and 110 and 121° E, covering a surface area of 1344 × 103 km2 and accounting for ~ 54% of the SCS proper. In the area off the Pearl River estuary, relatively low pCO2 values of 320 to 390 μatm were observed in all four seasons and both the biological productivity and CO2 uptake were enhanced in summer in the Pearl River plume waters. In the northern SCS slope/basin area, a typical seasonal cycle of relatively high pCO2 in the warm seasons and relatively low pCO2 in the cold seasons was revealed. In the central/southern SCS area, moderately high sea surface pCO2 values of 360 to 425 μatm were observed throughout the year. In the area west of the Luzon Strait, a major exchange pathway between the SCS and the Pacific Ocean, pCO2 was particularly dynamic in winter, when northeast monsoon induced upwelling events and strong outgassing of CO2. These episodic events might have dominated the annual sea–air CO2 flux in this particular area. The estimate of annual sea–air CO2 fluxes showed that most areas of the SCS proper served as weak to moderate sources of the atmospheric CO2, with sea–air CO2 flux values of 0.46 ± 0.43 mol m−2 yr−1 in the northern SCS slope/basin, 1.37 ± 0.55 mol m−2 yr−1 in the central/southern SCS, and 1.21 ± 1.48 mol m−2 yr−1 in the area west of the Luzon Strait. However, the annual sea–air CO2 exchange was nearly in equilibrium (−0.44 ± 0.65 mol m−2 yr−1) in the area off the Pearl River estuary. Overall the four domains contributed (18 ± 10) × 1012 g C yr−1 to the atmospheric CO2.

scholarly journals A modeling study of temporal and spatial <i>p</i>CO<sub>2</sub> variability on the biologically active and temperature-dominated Scotian Shelf

2021 ◽  
Author(s):  
Krysten Rutherford ◽  
Katja Fennel ◽  
Dariia Atamanchuk ◽  
Douglas Wallace ◽  
Helmuth Thomas
Keyword(s):  
Surface Water ◽  
Coastal Upwelling ◽  
Gulf Of Maine ◽  
Dissolved Inorganic Carbon ◽  
Co2 Flux ◽  
General Assumption ◽  
Biologically Active ◽  
Source Surface ◽  
Scotian Shelf ◽  
Temporal And Spatial

Abstract. Continental shelves are thought to be affected disproportionately by climate change and are a large contributor to global air-sea carbon dioxide (CO2) fluxes. It is often reported that low-latitude shelves tend to act as net sources of CO2 whereas mid- and high-latitude shelves act as net sinks. Here, we combine a high-resolution regional model with surface water time-series and repeat transect observations from the Scotian Shelf, a mid-latitude region in the northwest North Atlantic, to determine what processes are driving the temporal and spatial variability of partial pressure of CO2 (pCO2). In contrast to the global trend, the Scotian Shelf acts as a net source. Surface pCO2 undergoes a strong seasonal cycle associated with both a strong biological drawdown of Dissolved Inorganic Carbon (DIC) in spring, and pronounced effects of temperature, which ranges from 0 °C in the winter to near 20 °C in the summer. Throughout the summer, events with low surface-water pCO2 occur nearshore associated with coastal upwelling. This effect of upwelling on pCO2 is also in contrast to the general assumption that upwelling increases surface pCO2 by delivering DIC-enriched water to the surface. Aside from these localized events, pCO2 is relatively uniform across the shelf. Our model agrees with regional observations, reproduces seasonal patterns of pCO2, and simulates annual outgassing of CO2 from the ocean of +1.9 ± 0.2 mol C m−2 yr−1 for the Scotian Shelf, net neutral CO2 flux of −0.09 ± 0.16 mol C m−2 yr−1 for the Gulf of Maine and uptake by the ocean of −0.88 ± 0.4 mol C m−2 yr−1 for the Grand Banks.

Circulation, dispersion and hydrodynamic connectivity over the Scotian Shelf and adjacent waters

2017 ◽  
Vol 2 (2) ◽  
Author(s):  
Yi Sui ◽  
Jinyu Sheng ◽  
Kyoko Ohashi ◽  
Yongsheng Wu
Keyword(s):  
Ocean Circulation ◽  
Surface Waters ◽  
Gulf Of Maine ◽  
Scotian Shelf ◽  
Study Region ◽  
Near Surface ◽  
Tidal Forcing ◽  
Surface Dispersion ◽  
Tracking Model ◽  
Modelling System

A nested-grid ocean circulation modelling system is used in this study to examine the circulation of surface waters over the Scotian Shelf and its adjacent waters. The modelling system consists of a coarse-resolution (1/12°) barotropic storm surge (outer) model covering the northwest Atlantic Ocean, and a fine-resolution (1/16°) baroclinic (inner) model covering the Gulf of St. Lawrence, Scotian Shelf, and Gulf of Maine. The external model forcing includes tidal forcing, atmospheric forcing, surface heat fluxes, freshwater discharge, and large-scale currents specified at model open boundaries. The three-dimensional model currents are used to track trajectories of particles using a Lagrangian particle-tracking model. The simulated particle movements and distributions are used to examine the dispersion, retention, and hydrodynamic connectivity of surface waters over the study region. The near-surface dispersion is relatively high over western Cabot Strait, the inner Scotian Shelf, and the shelf break of the Scotian Shelf, while relatively low in Northumberland Strait. A process study is conducted to examine the physical processes affecting the surface dispersion, including tidal forcing and local wind forcing. The model results show that the tidal currents significantly influence the dispersion of surface waters in the Bay of Fundy.

scholarly journals A Novel Approach To Quantify Air–Water Gas Exchange in Shallow Surface Waters Using High-Resolution Time Series of Dissolved Atmospheric Gases

2018 ◽  
Vol 53 (3) ◽  
pp. 1463-1470 ◽  
Author(s):  
Ulrich W. Weber ◽  
Peter G. Cook ◽  
Matthias S. Brennwald ◽  
Rolf Kipfer ◽  
Thomas C. Stieglitz
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Gas Exchange ◽  
Surface Waters ◽  
Atmospheric Gases ◽  
Resolution Time ◽  
Novel Approach ◽  
Water Gas

scholarly journals Can CMIP5 Earth System Models Reproduce the Interannual Variability of Air–Sea CO2 Fluxes over the Tropical Pacific Ocean?

2019 ◽  
Vol 32 (8) ◽  
pp. 2261-2275 ◽  
Author(s):  
Chenxi Jin ◽  
Tianjun Zhou ◽  
Xiaolong Chen
Keyword(s):  
Surface Temperature ◽  
Interannual Variability ◽  
El Niño ◽  
El Nino ◽  
Co2 Flux ◽  
Sea Surface ◽  
Co2 Fluxes ◽  
Earth System ◽  
Earth System Models ◽  
The Tropical Pacific

Abstract Interannual variability of air–sea CO2 exchange is an important metric that represents the interaction between the carbon cycle and climate change. Although previous studies report a large bias in the CO2 flux interannual variability in many Earth system models (ESMs), the reason for this bias remains unclear. In this study, the performance of ESMs in phase 5 of the Coupled Model Intercomparison Project (CMIP5) is assessed in the context of the variability of air–sea CO2 flux over the tropical Pacific related to El Niño–Southern Oscillation (ENSO) using an emission-driven historical experiment. Using empirical orthogonal function (EOF) analysis, the first principal component of air–sea CO2 flux shows a significant relationship with the Niño-3.4 index in both the observation-based product and models. In the observation-based product, the spatial pattern of EOF1 shows negative anomalies in the central Pacific, which is, however, in contrast to those in several ESMs, and even opposite in sign to those in HadGEM2-ES and MPI-ESM-LR. The unrealistic response of the air–sea CO2 flux to ENSO mainly originates from the biases in the anomalous surface-water CO2 partial pressure (). A linear Taylor expansion by decomposing the anomalous into contributions from salinity, sea surface temperature, dissolved inorganic carbon (DIC), and alkalinity is applied to diagnose the biases. The results show that decreased during El Niño results from reduced upwelling of high-concentration DIC from deeper layers that overwhelms the increasing caused by warmer sea surface temperature. Overly weak reduction of vertical motion during El Niño and weak vertical gradients of climatological DIC concentration are the main reasons for biases in the negative surface DIC anomalies and eventually the anomalies. This study highlights the importance of both physical ocean responses to El Niño and climatological distributions of carbon-related tracers in the simulation of the interannual variability of air–sea CO2 fluxes.

scholarly journals Seasonal variations of air-sea CO<sub>2</sub> fluxes in the largest tropical marginal sea (South China Sea) based on multiple-year underway measurements

2013 ◽  
Vol 10 (4) ◽  
pp. 7031-7074
Author(s):  
W.-D. Zhai ◽  
M.-H. Dai ◽  
B.-S. Chen ◽  
X.-H. Guo ◽  
Q. Li ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
River Estuary ◽  
Co2 Flux ◽  
Pearl River Estuary ◽  
Sea Surface ◽  
Pearl River ◽  
Co2 Fluxes ◽  
China Sea ◽  
The Pearl River

Abstract. Based upon fourteen field surveys conducted between 2003 and 2008, we showed that the seasonal pattern of sea surface partial pressure of CO2 (pCO2) and air–sea CO2 fluxes differed among four different physical-biogeochemical domains in the South China Sea (SCS) proper. The four domains were located between 4 and 23° N and 109 and 121° E, covering ~ 38% of the surface area of the entire SCS. In the area off the Pearl River Estuary, relatively low pCO2 values of 320 to 390 μatm were observed in all four seasons and both the biological productivity and CO2 uptake were enhanced in summer in the Pearl River plume waters. In the northern SCS slope/basin area, a typical seasonal cycle of relatively high pCO2 in the warmer seasons and relatively low pCO2 in the cold seasons was revealed. In the central/southern SCS area, moderately high sea surface pCO2 values of 360 to 425 μatm were observed throughout the year. In the area west of the Luzon Strait, a major exchange pathway between the SCS and the Pacific Ocean, pCO2 was particularly dynamic in winter, when northeast monsoon induced upwelling events and strong outgassing of CO2. These episodic events might have dominated the annual air–sea CO2 flux in this particular area. The estimate of annual sea–air CO2 fluxes showed that, most areas of the SCS proper served as weak sources to the atmospheric CO2, with sea–air CO2 flux values of 0.46 ± 0.43 mol m−2 yr−1 in the northern SCS slope/basin, 1.37 ± 0.55 mol m−2 yr−1 in the central/southern SCS, and 1.21 ± 1.47 mol m−2 yr−1 in the area west of the Luzon Strait. However, the annual sea–air CO2 exchange was nearly in equilibrium (−0.44 ± 0.65 mol m−2 yr−1) in the area off the Pearl River Estuary. Overall the four domains released (18 ± 10) × 1012 g C yr−1 into the atmosphere. The CO2 release rate of the South China Sea essentially exceeded the average CO2 emission level of most tropical oceans.

EXTREME VALUES OF SEA SURFACE TEMPERATURE ASSOCIATED WITH LONG-PERIOD PHENOMENA OCCURRED DURING 1960-2015 IN THE COLOMBIAN PACIFIC OCEAN

2017 ◽  
Author(s):  
Diaz Juan Navia ◽  
Diaz Juan Navia ◽  
Bolaños Nancy Villegas ◽  
Bolaños Nancy Villegas ◽  
Igor Malikov ◽  
...  
Keyword(s):  
Time Series ◽  
Pacific Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Extreme Values ◽  
Sea Surface ◽  
Absolute Maximum ◽  
Data Set ◽  
Arctic Oscillation Index ◽  
Colombian Pacific

Sea Surface Temperature Anomalies (SSTA), in four coastal hydrographic stations of Colombian Pacific Ocean, were analyzed. The selected hydrographic stations were: Tumaco (1°48'N-78°45'W), Gorgona island (2°58'N-78°11'W), Solano Bay (6°13'N-77°24'W) and Malpelo island (4°0'N-81°36'W). SSTA time series for 1960-2015 were calculated from monthly Sea Surface Temperature obtained from International Comprehensive Ocean Atmosphere Data Set (ICOADS). SSTA time series, Oceanic Nino Index (ONI), Pacific Decadal Oscillation index (PDO), Arctic Oscillation index (AO) and sunspots number (associated to solar activity), were compared. It was found that the SSTA absolute minimum has occurred in Tumaco (-3.93°C) in March 2009, in Gorgona (-3.71°C) in October 2007, in Solano Bay (-4.23°C) in April 2014 and Malpelo (-4.21°C) in December 2005. The SSTA absolute maximum was observed in Tumaco (3.45°C) in January 2002, in Gorgona (5.01°C) in July 1978, in Solano Bay (5.27°C) in March 1998 and Malpelo (3.64°C) in July 2015. A high correlation between SST and ONI in large part of study period, followed by a good correlation with PDO, was identified. The AO and SSTA have showed an inverse relationship in some periods. Solar Cycle has showed to be a modulator of behavior of SSTA in the selected stations. It was determined that extreme values of SST are related to the analyzed large scale oscillations.

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