J. E. Salisbury

Publications (8)5.97 Total impact

• Source

  Available from: Christopher Hunt

  Article: Contribution of non-carbonate anions to total alkalinity and overestimation of pCO2 in New England and New Brunswick rivers

  C.W. Hunt, J.E. Salisbury, D. Vandemark
  [show abstract] [hide abstract]
  ABSTRACT: Total alkalinity (TAlk) has long been used to evaluate the buffering capacity of aquatic systems. TAlk has also been used, together with measurements of either pH or dissolved inorganic carbon (DIC), to indirectly estimate the partial pressure of carbon dioxide (pCO2) in inland waters, estuaries, and marine systems. These estimates typically assume that carbonate and bicarbonate ions comprise nearly all the species contributing to TAlk; however, other inorganic and organic acids have the potential to contribute significant non-carbonate alkalinity. To evaluate the potential for error in using TAlk to estimate pCO2, we measured pH, TAlk, and DIC in samples of river water. Estimates of pCO2 derived from TAlk and pH measurements were higher than pCO2 estimates derived from DIC and pH by 13–66%. We infer that this overestimate is due to the presence of significant non-carbonate alkalinity (NC-Alk). This study also describes the relative proportions of carbonate- and non-carbonate alkalinity measured in 15 river systems located in northern New England (USA) and New Brunswick (Canada). NC-Alk represents a significant buffering component in these river systems (21–∼100% of TAlk), and failure to account for NC-Alk (which cannot directly contribute to pCO2) leads to the overestimation of carbon dioxide release to the atmosphere.
  Biogeosciences 01/2011; doi:10.5194/bg-8-3069-2011. · 3.86 Impact Factor
• Source

  Available from: Christopher Hunt

  Article: Contribution of non-carbonate anions to river alkalinity and overestimation of pCO 2

  C W Hunt, J E Salisbury, D Vandemark
  [show abstract] [hide abstract]
  ABSTRACT: Total alkalinity (TAlk) has long been used to evaluate the buffering capacity of aquatic systems. TAlk has also been used, together with measurements of either pH or dis-solved inorganic carbon (DIC), to indirectly estimate the partial pressure of carbon diox-ide (pCO 2) in inland waters, estuaries, and marine systems. These estimates typically 5 assume that carbonate and bicarbonate ions comprise nearly all the species contribut-ing to TAlk; however, other inorganic and organic acids have the potential to contribute significant non-carbonate alkalinity. To evaluate the potential for error in using TAlk to estimate pCO 2 , we measured pH, TAlk, and DIC in samples of river water. Estimates of pCO 2 derived from TAlk and pH measurements were markedly higher than pCO 2 esti-10 mates derived from DIC and pH. We infer that this overestimate is due to the presence of significant non-carbonate alkalinity (NC-Alk). This study also describes the relative proportions of carbonate-and non-carbonate alkalinity measured in 15 river systems located in northern New England and the Canadian Maritimes. NC-Alk represents a significant buffering component in these river systems, and failure to account for NC-15 Alk (which cannot directly contribute to pCO 2) leads to the overestimation of carbon dioxide release to the atmosphere.
  BGD. 01/2011; 8(8):5159-5177.
• Source

  Available from: Christopher Hunt

  Article: Temporal and spatial dynamics of CO2 air-sea flux in the Gulf of Maine

  D Vandemark, J E Salisbury, C W Hunt, S M Shellito, J D Irish, W R Mcgillis, C L Sabine, S M Maenner
  [show abstract] [hide abstract]
  ABSTRACT: 6 [1] Ocean surface layer carbon dioxide (CO 2) data collected in the Gulf of Maine from 7 2004 to 2008 are presented. Monthly shipboard observations are combined with additional 8 higher‐resolution CO 2 observations to characterize CO 2 fugacity (fCO 2) and CO 2 flux 9 over hourly to interannual time scales. Observed fCO 2 and CO 2 flux dynamics are dominated 10 by a seasonal cycle, with a large spring influx of CO 2 and a fall‐to‐winter efflux back to the 11 atmosphere. The temporal results at inner, middle, and outer shelf locations are highly 12 correlated, and observed spatial variability is generally small relative to the monthly to 13 seasonal temporal changes. The averaged annual flux is in near balance and is a net source 14 of carbon to the atmosphere over 5 years, with a value of +0.38 mol m −2 yr −1 . However, 15 moderate interannual variation is also observed, where years 2005 and 2007 represent 16 cases of regional source (+0.71) and sink (−0.11) anomalies. We use moored daily CO 2 17 measurements to quantify aliasing due to temporal undersampling, an important error budget 18 term that is typically unresolved. The uncertainty of our derived annual flux measurement is 19 ±0.26 mol m −2 yr −1 and is dominated by this aliasing term. Comparison of results to the 20 neighboring Middle and South Atlantic Bight coastal shelf systems indicates that the Gulf of 21 Maine exhibits a similar annual cycle and range of oceanic fCO 2 magnitude but differs 22 in the seasonal phase. It also differs by enhanced fCO 2 controls by factors other than 23 temperature‐driven solubility, including biological drawdown, fall‐to‐winter vertical 24 mixing, and river runoff.
  J. Geophys. Res. 01/2011; 116.
• Article: Air-Sea CO₂ fluxes on the Scotian Shelf: seasonal to multi-annual variability

  E. H. Shadwick, Thomas H, Comeau A, S. E. Craig, C. W. Hunt, J. E. Salisbury
  [show abstract] [hide abstract]
  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.
  Biogeosciences. 01/2010;
• Source

  Available from: Christopher Hunt

  Article: Contrasting Carbon Dioxide Inputs and Exchange in Three Adjacent New England Estuaries

  C.W. Hunt, J.E. Salisbury, D. Vandemark, W. McGillis
  [show abstract] [hide abstract]
  ABSTRACT: Four surveys of the adjacent Cocheco, Bellamy, and Oyster estuaries reveal spatial heterogeneity with respect both to river-born carbon dioxide (CO2) fluxes and CO2 exchange with the atmosphere (−17 to 51 mmol m−2day−1), a finding partially explained by CO2 inputs from contributing watersheds. Nonuniform nutrient and organic carbon loading from upstream rivers and within the estuaries is considered as a mechanism resulting in the variability between estuaries. Conditions during the surveys included spring river runoff and phytoplankton blooms, drought with baseline river flow, and a historic flood which led to a large CO2 release to the atmosphere. This study highlights the variability of CO2 transport and release found between proximate estuaries over a wide range of flow conditions.
  Estuaries and Coasts 01/2010; doi 10.1007/s12237-010-9299-9. · 2.11 Impact Factor
• Source

  Available from: biogeosciences-discuss.net

  Article: Large variability in continental shelf production of phytoplankton carbon revealed by satellite

  B. F. Jönsson, J. E. Salisbury, Mahadevan A
  [show abstract] [hide abstract]
  ABSTRACT: We estimate the net production of phytoplankton in the Gulf of Maine (GoM) over a 3-year period using satellite ocean color data in conjunction with surface velocities from a high-resolution operational ocean circulation model. Chlorophyll (chl-a) and light attenuation (K490) products are combined with a carbon to chlorophyll model to estimate the phytoplankton carbon (PC) stock in the euphotic layer. A satellite-based productivity, termed NCPe in analogy with net community production (NCP), is derived by tracking changes in satellite-derived PC from one satellite image to the next, along water parcel trajectories calculated with surface velocities from the ocean circulation model. Such an along-trajectory analysis of satellite data discounts the effect of advection that would otherwise contribute to the temporal change between consecutive images viewed in the fixed reference frame. Our results show a high variability of up to ± 500 mg C m−2 d−1 in NCPe on spatial scales of 10–100 km. A region-wide median NCPe of 40–50 mg C m−2 d−1 is often prevalent in the Gulf, while blooms attain peak values of 400 mg C m−2 d−1 for a few days. The spatio-temporal variability of NCPe in this region, though conditioned by seasonality, is dominated by events lasting a few days, which if integrated, lead to large inter-annual variability in the annual carbon budget. This study is a step toward achieving synoptic and time-dependent estimates of oceanic productivity and NCP from satellite data.
  Biogeosciences Discussions. 01/2010;
• Source

  Available from: Christopher Hunt

  Article: Satellite observations reveal high variability and a decreasing trend in CO₂ fluxes on the Scotian Shelf

  E. H. Shadwick, Thomas H, Comeau A, S. E. Craig, C. W. Hunt, J. E. Salisbury
  [show abstract] [hide abstract]
  ABSTRACT: We develop an algorithm to compute p CO₂ 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 p CO₂ 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 p CO₂ 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.
  Biogeosciences Discussions. 01/2010;
• Source

  Available from: Susanne Craig

  Article: Air-Sea CO2 fluxes on the Scotian Shelf: seasonal to multi-annual variability

  E. H. Shadwick, H. Thomas, A. Comeau, S. E. Craig, C. W. Hunt, J. E. Salisbury
  Biogeosciences. 7(11):3851-3867.