Investigations of air-sea gas exchange in the CoOP Coastal Air-Sea Chemical Exchange project

Author Posting. © Oceanography Society, 2008. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 21, 4 (2008): 34-45.The exchange of CO2 and other gases across the ocean-air interface is an extremely important component in global climate dynamics, photosynthesis and respiration, and the absorption of anthropogenically produced CO2. The many different mechanisms and properties that control the air-sea flux of CO2 can have large spatial and temporal variability, particularly in the coastal environment. The need for making short-time-scale and small-spatial-scale estimates of gas transfer velocity, along with the physical and chemical parameters that affect it, provided a framework for the field experiments of the Coastal Ocean Processes Program (CoOP) Coastal Air-Sea Chemical Exchange (CASCEX) program. As such, the CASCEX project provided an opportunity to develop some of the first in situ techniques to estimate gas fluxes using micrometeorological and thermal imagery techniques. The results reported from the CASCEX experiments represent the first step toward reconciling the indirect but widely accepted estimates of gas exchange with these more direct, higher-resolution estimates over the coastal ocean. These results and the advances in sensor technology initiated during the CASCEX project have opened up even larger regions of the global ocean to investigation of gas exchange and its role in climate change.Funding for this work was provided by the National Science Foundation (NSF) CoOP program under grants OCE-9410534 and OCE-9711285

Sea surface pCO2 and O2 dynamics in the partially ice-covered Arctic Ocean

Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 1425–1438, doi:10.1002/2016JC012162.Understanding the physical and biogeochemical processes that control CO2 and dissolved oxygen (DO) dynamics in the Arctic Ocean (AO) is crucial for predicting future air-sea CO2 fluxes and ocean acidification. Past studies have primarily been conducted on the AO continental shelves during low-ice periods and we lack information on gas dynamics in the deep AO basins where ice typically inhibits contact with the atmosphere. To study these gas dynamics, in situ time-series data have been collected in the Canada Basin during late summer to autumn of 2012. Partial pressure of CO2 (pCO2), DO concentration, temperature, salinity, and chlorophyll-a fluorescence (Chl-a) were measured in the upper ocean in a range of sea ice states by two drifting instrument systems. Although the two systems were on average only 222 km apart, they experienced considerably different ice cover and external forcings during the 40–50 day periods when data were collected. The pCO2 levels at both locations were well below atmospheric saturation whereas DO was almost always slightly supersaturated. Modeling results suggest that air-sea gas exchange, net community production (NCP), and horizontal gradients were the main sources of pCO2 and DO variability in the sparsely ice-covered AO. In areas more densely covered by sea ice, horizontal gradients were the dominant source of variability, with no significant NCP in the surface mixed layer. If the AO reaches equilibrium with atmospheric CO2 as ice cover continues to decrease, aragonite saturation will drop from a present mean of 1.00 ± 0.02 to 0.86 ± 0.01.U.S. National Science Foundation Arctic Observing Network Grant Number: ARC-1107346 and ARC-08564792017-08-2

Sea surface pCO2 and O2 in the Southern Ocean during the austral fall, 2008

The physical and biological processes controlling surface mixed layer pCO2 and O2 were evaluated using in situ sensors mounted on a Lagrangian drifter deployed in the Atlantic sector of the Southern Ocean (∼50°S, ∼37°W) during the austral fall of 2008. The drifter was deployed three times during different phases of the study. The surface ocean pCO2 was always less than atmospheric pCO2 (−50.4 to −76.1 μatm), and the ocean was a net sink for CO2 with fluxes averaging between 16.2 and 17.8 mmol C m−2 d−1. Vertical entrainment was the dominant process controlling mixed layer CO2, with fluxes that were 1.8 to 2.2 times greater than the gas exchange fluxes during the first two drifter deployments, and was 1.7 times greater during the third deployment. In contrast, during the first two deployments the surface mixed layer was always a source of O2 to the atmosphere, and air-sea gas exchange was the dominant process occurring, with fluxes that were 2.0 to 4.1 times greater than the vertical entrainment flux. During the third deployment O2 was near saturation the entire deployment and was a small source of O2 to the atmosphere. Net community production (NCP) was low during this study, with mean fluxes of 3.2 to 6.4 mmol C m−2 d−1 during the first deployment and nondetectable (within uncertainty) in the third. During the second deployment the NCP was not separable from lateral advection. Overall, this study indicates that in the early fall the area is a significant sink for atmospheric CO2

Uptake and sequestration of atmospheric CO2 in the Labrador Sea deep convection region

The Labrador Sea is an important area of deep water formation and is hypothesized to be a significant sink for atmospheric CO2 to the deep ocean. Here we examine the dynamics of the CO2 system in the Labrador Sea using time-series data obtained from instrumentation deployed on a mooring near the former Ocean Weather Station Bravo. A 1-D model is used to determine the air-sea CO2 uptake and penetration of the CO2 into intermediate waters. The results support that mixed-layer pCO2 remained undersaturated throughout most of the year, ranging from 220 μatm in mid-summer to 375 μatm in the late spring. Net community production in the summer offset the increase in pCO2 expected from heating and air-sea uptake. In the fall and winter, cooling counterbalanced a predicted increase in pCO2 from vertical convection and air-sea uptake. The predicted annual mean air to sea flux was 4.6 mol m−2 yr−1 resulting in an annual uptake of 0.011 ± 0.005 Pg C from the atmosphere within the convection region. In 2001, approximately half of the atmospheric CO2 penetrated below 500 m due to deep convection

Ocean time series observations of changing marine ecosystems: An era of integration, synthesis, and societal applications

Sustained ocean time series are critical for characterizing marine ecosystem shifts in a time of accelerating, and at times unpredictable, changes. They represent the only means to distinguish between natural and anthropogenic forcings, and are the best tools to explore causal links and implications for human communities that depend on ocean resources. Since the inception of sustained ocean observations, ocean time series have withstood many challenges, most prominently availability of uninterrupted funding and retention of trained personnel. This OceanObs’19 review article provides an overarching vision for sustained ocean time series observations for the next decade, focusing on the growing challenges of maintaining sustained ocean time series, including ship-based and autonomous coastal and open-ocean platforms, as well as remote sensing. In addition to increased diversification of funding sources to include the private sector, NGOs, and other groups, more effective engagement of stakeholders and other end-users will be critical to ensure the sustainability of ocean time series programs. Building a cohesive international time series network will require dedicated capacity to coordinate across observing programs and leverage existing infrastructure and platforms of opportunity. This review article outlines near-term observing priorities and technology needs; explores potential mechanisms to broaden ocean time series data applications and end-user communities; and describes current tools and future requirements for managing increasingly complex multi-platform data streams and developing synthesis products that support science and society. The actionable recommendations outlined herein ultimately form the basis for a robust, sustainable, fit-for-purpose time series network that will foster a predictive understanding of changing ocean systems for the benefit of society

Biases in the air-sea flux of CO2 resulting from ocean surface temperature gradients

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C08S08, doi:10.1029/2003JC001800.The difference in the fugacities of CO2 across the diffusive sublayer at the ocean surface is the driving force behind the air-sea flux of CO2. Bulk seawater fugacity is normally measured several meters below the surface, while the fugacity at the water surface, assumed to be in equilibrium with the atmosphere, is measured several meters above the surface. Implied in these measurements is that the fugacity values are the same as those across the diffusive boundary layer. However, temperature gradients exist at the interface due to molecular transfer processes, resulting in a cool surface temperature, known as the skin effect. A warm layer from solar radiation can also result in a heterogeneous temperature profile within the upper few meters of the ocean. Here we describe measurements carried out during a 14-day study in the equatorial Pacific Ocean (GasEx-2001) aimed at estimating the gradients of CO2 near the surface and resulting flux anomalies. The fugacity measurements were corrected for temperature effects using data from the ship's thermosalinograph, a high-resolution profiler (SkinDeEP), an infrared radiometer (CIRIMS), and several point measurements at different depths on various platforms. Results from SkinDeEP show that the largest cool skin and warm layer biases occur at low winds, with maximum biases of −4% and +4%, respectively. Time series ship data show an average CO2 flux cool skin retardation of about 2%. Ship and drifter data show significant CO2 flux enhancement due to the warm layer, with maximums occurring in the afternoon. Temperature measurements were compared to predictions based on available cool skin parameterizations to predict the skin-bulk temperature difference, along with a warm layer model.This material is based upon work supported by the NSF under grant OCE-9986724, and by NOAA/OGP grant GC00-226

Impact of Attention-Deficit/Hyperactivity Disorder (ADHD) on prescription dug spending for children and adolescents: increasing relevance of health economic evidence

<p>Abstract</p> <p>Background</p> <p>During the last decade, pharmaceutical spending for patients with attention-deficit-hyperactivity disorder (ADHD) has been escalating internationally.</p> <p>Objectives</p> <p>First, to estimate future trends of ADHD-related drug expenditures from the perspectives of the statutory health insurance (SHI; Gesetzliche Krankenversicherung, GKV) in Germany and the National Health Service (NHS) in England, respectively, for children and adolescents age 6 to 18 years. Second, to evaluate the budgetary impact on individual prescribers (child and adolescent psychiatrists and pediatricians treating patients with ADHD) in Germany.</p> <p>Methods</p> <p>A model was developed to predict plausible scenarios of future pharmaceutical expenditures for treatment of ADHD. Model inputs were derived from demographic and epidemiological data, a literature review of past spending trends, and an analysis of new pharmaceutical products in development for ADHD. Only products in clinical development phase III or later were considered. Uncertainty was addressed by way of scenario analysis. For each jurisdiction, five scenarios used different assumptions of future diagnosis prevalence, treatment prevalence, rates of adoption and unit costs of novel drugs, and treatment intensity.</p> <p>Results</p> <p>Annual ADHD pharmacotherapy expenditures for children and adolescents will further increase and may exceed €310 m (D; E: ₤78 m) in 2012 (2002: ~€21.8 m; ~₤7.0 m). During this period, overall drug spending by individual physicians may increase 2.3- to 9.5-fold, resulting from the multiplicative effects of four variables: increased number of diagnosed cases, growing acceptance and intensity of pharmacotherapy, and higher unit costs of novel medications.</p> <p>Discussion</p> <p>Even for an extreme low case scenario, a more than six-fold increase of pharmaceutical spending for children and adolescents is predicted over the decade from 2002 to 2012, from the perspectives of both the NHS in England and the GKV in Germany. This budgetary impact projection represents a partial analysis only because other expenditures are likely to rise as well, for instance those associated with physician services, including diagnosis and psychosocial treatment. Further to this, by definition budgetary impact analyses have little to nothing to say about clinical appropriateness and about value of money.</p> <p>Conclusion</p> <p>Providers of care for children and adolescents with ADHD should anticipate serious challenges related to the cost-effectiveness of interventions.</p

Estimates of new and total productivity in central Long Island Sound from in situ measurements of nitrate and dissolved oxygen

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Estuaries and Coasts 36 (2013): 74-97, doi:10.1007/s12237-012-9560-5.Biogeochemical cycles in estuaries are regulated by a diverse set of physical and biological variables that operate over a variety of time scales. Using in situ optical sensors, we conducted a high-frequency time-series study of several biogeochemical parameters at a mooring in central Long Island Sound from May to August 2010. During this period, we documented well-defined diel cycles in nitrate concentration that were correlated to dissolved oxygen, wind stress, tidal mixing, and irradiance. By filtering the data to separate the nitrate time series into various signal components, we estimated the amount of variation that could be ascribed to each process. Primary production and surface wind stress explained 59% and 19%, respectively, of the variation in nitrate concentrations. Less frequent physical forcings, including large-magnitude wind events and spring tides, served to decouple the relationship between oxygen, nitrate, and sunlight on about one-quarter of study days. Daytime nitrate minima and dissolved oxygen maxima occurred nearly simultaneously on the majority (> 80%) of days during the study period; both were strongly correlated with the daily peak in irradiance. Nighttime nitrate maxima reflected a pattern in which surface-layer stocks were depleted each afternoon and recharged the following night. Changes in nitrate concentrations were used to generate daily estimates of new primary production (182 ± 37 mg C m-2 d-1) and the f-ratio (0.25), i.e., the ratio of production based on nitrate to total production. These estimates, the first of their kind in Long Island Sound, were compared to values of community respiration, primary productivity, and net ecosystem metabolism, which were derived from in situ measurements of oxygen concentration. Daily averages of the three metabolic parameters were 1660 ± 431, 2080 ± 419, and 429 ± 203 mg C m-2 d-1, respectively. While the system remained weakly autotrophic over the duration of the study period, we observed very large day-to-day differences in the f-ratio and in the various metabolic parameters.This work was supported by the Yale Institute for Biospheric Studies, the Sounds Conservancy of the Quebec-Labrador Foundation, and the Yale School of Forestry and Environmental Studies Carpenter-Sperry Fund.2014-01-0

Simultaneous mooring‐based measurements of seawater CO2 and O2 off Cape Hatteras, North Carolina

We deployed CO2 and O2 sensors on the U.S. continental shelf off Cape Hatteras, North Carolina, during late summer 1994. A continuous 32‐d gas record was obtained at 20 m in 25 m of water, below the thermocline for most of the period. Analysis of the correlation between CO2 and O2 indicates that biological and advective processes dominated the gas variability, with small or insignificant fluxes due to air–sea exchange, vertical eddy diffusion, and carbonate dissolution or formation. The observed O2 : CO2 correlation was 1.39, within the range predicted for the photosynthetic quotient. Photosynthesis and respiration appeared to be tightly coupled, resulting in no net community production in these waters during the late summer. It is evident from these results that the combination of mooring‐based CO2 and O2 measurements will be a powerful tool for studying the marine carbon cycle