Toward a mechanistic understanding of the decadal trends in the Southern Ocean carbon sink

Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 22 (2008): GB3016, doi:10.1029/2007GB003139.We investigate the multidecadal and decadal trends in the flux of CO2 between the atmosphere and the Southern Ocean using output from hindcast simulations of an ocean circulation model with embedded biogeochemistry. The simulations are run with NCEP-1 forcing under both preindustrial and historical atmospheric CO2 concentrations so that we can separately analyze trends in the natural and anthropogenic CO2 fluxes. We find that the Southern Ocean (<35°S) CO2 sink has weakened by 0.1 Pg C a−1 from 1979–2004, relative to the expected sink from rising atmospheric CO2 and fixed physical climate. Although the magnitude of this trend is in agreement with prior studies (Le Quéré et al., 2007), its size may not be entirely robust because of uncertainties associated with the trend in the NCEP-1 atmospheric forcing. We attribute the weakening sink to an outgassing trend of natural CO2, driven by enhanced upwelling and equatorward transport of carbon-rich water, which are caused by a trend toward stronger and southward shifted winds over the Southern Ocean (associated with the positive trend in the Southern Annular Mode (SAM)). In contrast, the trend in the anthropogenic CO2 uptake is largely unaffected by the trend in the wind and ocean circulation. We regard this attribution of the trend as robust, and show that surface and interior ocean observations may help to solidify our findings. As coupled climate models consistently show a positive trend in the SAM in the coming century [e.g., Meehl et al., 2007], these mechanistic results are useful for projecting the future behavior of the Southern Ocean carbon sink.This work was supported by funding from various agencies. NSL was supported by NASA grant NNG05GP78H and the NOAA Climate and Global Change postdoctoral fellowship. NG was supported by NASA grant NNG04GH53G and by ETH Zurich. SCD was supported by NASA grant NNG05GG30G

A Climate Change Atlas for the Ocean

Author Posting. © Oceanography Society, 2011. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 24, no. 2 (2011): 13–16, doi:10.5670/oceanog.2011.42.At both regional and national levels, there is an urgent need to develop a clear picture of how climate change will alter multiple environmental properties in the ocean. Specifically, what will such cumulative alterations mean for local biological productivity, ecosystem services, climate feedbacks, and related effects ranging from biodiversity to economics? Currently, a wide range of confounding issues, such as the plethora and complexity of information in the public domain, hinders accommodating climate change into future planning and development of ocean resource management strategies. This impediment is especially true at the regional level, for example, within national Exclusive Economic Zones (EEZs), where critical management decisions are made but for which substantial uncertainty clouds climate change projections and ecosystem impact assessments. Evaluating the susceptibility of a nation's marine resources to climate change requires knowledge of the geographic and seasonal variations in environmental properties over an EEZ and the range, spatial patterns, and uncertainty of projected climate change in those properties (Boyd et al., 2007). Furthermore, information is needed on the climate sensitivity of the biological species or strains that comprise particular marine resources (Boyd et al., 2007; Nye et al., 2009) and/or contribute to food-web interactions, and also on potential implications for human resource exploitation patterns and intensity

Eddy-Modified Iron, Light, and Phytoplankton Cell Division Rates in the Simulated Southern Ocean

We examine the effects of Southern Ocean eddies on phytoplankton cell division rates in a global, multiyear, eddy‐resolving, 3‐D ocean simulation of the Community Earth System Model. We first identify and track eddies in the simulation and validate their distribution and demographics against observed eddy trajectory characteristics. Next, we examine how simulated cyclones and anticyclones differentially modify iron, light, and ultimately population‐specific cell division rates. We use an eddy‐centric, depth‐averaged framework to explicitly examine the dynamics of the phytoplankton population across the entire water column within an eddy. We find that population‐averaged iron availability is elevated in anticyclones throughout the year. The dominant mechanism responsible for vertically transporting iron from depth in anticyclones is eddy‐induced Ekman upwelling. During winter, in regions with deep climatological mixed layer depths, anticyclones also induce anomalously deep mixed layer depths, which further supply new iron from depth via an increased upward mixing flux. However, this additional contribution comes at the price of deteriorating light availability as biomass is distributed deeper in the water column. Therefore, even though population‐averaged specific division rates are elevated in Southern Ocean anticyclones throughout most of the year, in the winter, severe light stress can dominate relieved iron stress and lead to depressed division rates in some anticyclones, particularly in the deep mixing South Pacific Antarctic Circumpolar Current. The opposite is true in cyclones, which exhibit a consistently symmetric physical and biogeochemical response relative to anticyclones

The Simulated Biological Response to Southern Ocean Eddies via Biological Rate Modification and Physical Transport

We examine the structure and drivers of anomalous phytoplankton biomass in Southern Ocean eddies tracked in a global, multiyear, eddy-resolving, 3-D ocean simulation of the Community Earth System Model.We examine how simulated anticyclones and cyclones differentially modify phytoplankton biomass concentrations, growth rates, and physical transport. On average, cyclones induce negative division rate anomalies that drive negative net population growth rate anomalies, reduce dilution across shallower mixed layers, and advect biomass anomalously downward via eddy-induced Ekman pumping. The opposite is true in anticyclones. Lateral transport is dominated by eddy stirring rather than eddy trapping. The net effect on anomalous biomass can exceed 10–20% of background levels at the regional scale, consistent with observations. Moreover, we find a strong seasonality in the sign and magnitude of regional anomalies and the processes that drive them. The most dramatic seasonal cycle is found in the South Pacific Antarctic Circumpolar Current, where physical and biological processes dominate at different times, modifying biomass in different directions throughout the year. Here, in cyclones, during winter, anomalously shallow mixed layer depths first drive positive surface biomass anomalies via reduced dilution, and later drive positive depth-integrated biomass anomalies via reduced light limitation. During spring, reduced iron availability and elevated grazing rates suppress net population growth rates and drive the largest annual negative surface and depth-integrated biomass anomalies. During summer and fall, lateral stirring and eddy-induced Ekman pumping create small negative surface anomalies but positive depth-integrated anomalies. The same mechanisms drive biomass anomalies in the opposite direction in anticyclones

Modeling of the Influence of Sea Ice Cycle and Langmuir Circulation on the Upper Ocean Mixed Layer Depth and Freshwater Distribution at the West Antarctic Peninsula.

The Southern Ocean is chronically undersampled due to its remoteness, harsh environment, and sea ice cover. Ocean circulation models yield significant insight into key processes and to some extent obviate the dearth of data; however, they often underestimate surface mixed layer depth (MLD), with consequences for surface water-column temperature, salinity, and nutrient concentration. In this study, a coupled circulation and sea ice model was implemented for the region adjacent to the West Antarctic Peninsula, a climatically sensitive region which has exhibited decadal trends towards higher ocean temperature, shorter sea ice season, and increasing glacial freshwater input, overlain by strong interannual variability. Hindcast simulations were conducted with different air-ice drag coefficients and Langmuir circulation parameterizations to determine the impact of these factors on MLD. Including Langmuir circulation deepened the surface mixed layer, with the deepening being more pronounced in the shelf and slope regions. Optimal selection of an air-ice drag coefficient also increased modeled MLD by similar amounts and had a larger impact in improving the reliability of the simulated MLD interannual variability. This study highlights the importance of sea ice volume and redistribution to correctly reproduce the physics of the underlying ocean, and the potential of appropriately parameterizing Langmuir circulation to help correct for biases towards shallow MLD in the Southern Ocean. The model also reproduces observed freshwater patterns in the West Antarctic Peninsula during late summer and suggests that areas of intense summertime sea ice melt can still show net annual freezing due to high sea ice formation during the winter

Modeling polar marine ecosystem functions guided by bacterial physiological and taxonomic traits

Heterotrophic marine bacteria utilize organic carbon for growth and biomass synthesis. Thus, their physiological variability is key to the balance between the production and consumption of organic matter and ultimately particle export in the ocean. Here we investigate a potential link between bacterial traits and ecosystem functions in the rapidly warming West Antarctic Peninsula (WAP) region based on a bacteria-oriented ecosystem model. Using a data assimilation scheme, we utilize the observations of bacterial groups with different physiological traits to constrain the group-specific bacterial ecosystem functions in the model. We then examine the association of the modeled bacterial and other key ecosystem functions with eight recurrent modes representative of different bacterial taxonomic traits. Both taxonomic and physiological traits reflect the variability in bacterial carbon demand, net primary production, and particle sinking flux. Numerical experiments under perturbed climate conditions demonstrate a potential shift from low nucleic acid bacteria to high nucleic acid bacteria-dominated communities in the coastal WAP. Our study suggests that bacterial diversity via different taxonomic and physiological traits can guide the modeling of the polar marine ecosystem functions under climate change

Carbon source/sink information provided by column CO2 measurements from the Orbiting Carbon Observatory

© The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Atmospheric Chemistry and Physics 10 (2010): 4145-4165, doi:10.5194/acp-10-4145-2010.We quantify how well column-integrated CO2 measurements from the Orbiting Carbon Observatory (OCO) should be able to constrain surface CO2 fluxes, given the presence of various error sources. We use variational data assimilation to optimize weekly fluxes at a 2°×5° resolution (lat/lon) using simulated data averaged across each model grid box overflight (typically every ~33 s). Grid-scale simulations of this sort have been carried out before for OCO using simplified assumptions for the measurement error. Here, we more accurately describe the OCO measurements in two ways. First, we use new estimates of the single-sounding retrieval uncertainty and averaging kernel, both computed as a function of surface type, solar zenith angle, aerosol optical depth, and pointing mode (nadir vs. glint). Second, we collapse the information content of all valid retrievals from each grid box crossing into an equivalent multi-sounding measurement uncertainty, factoring in both time/space error correlations and data rejection due to clouds and thick aerosols. Finally, we examine the impact of three types of systematic errors: measurement biases due to aerosols, transport errors, and mistuning errors caused by assuming incorrect statistics. When only random measurement errors are considered, both nadir- and glint-mode data give error reductions over the land of ~45% for the weekly fluxes, and ~65% for seasonal fluxes. Systematic errors reduce both the magnitude and spatial extent of these improvements by about a factor of two, however. Improvements nearly as large are achieved over the ocean using glint-mode data, but are degraded even more by the systematic errors. Our ability to identify and remove systematic errors in both the column retrievals and atmospheric assimilations will thus be critical for maximizing the usefulness of the OCO data.SD and DB acknowledge support from NASA grant NNG06G127G. DB also acknowledges initial support from NOAA Grant NA16GP2935

Toward a mechanistic understanding of the decadal trends

[1] We investigate the multidecadal and decadal trends in the flux of CO 2 between the atmosphere and the Southern Ocean using output from hindcast simulations of an ocean circulation model with embedded biogeochemistry. The simulations are run with NCEP-1 forcing under both preindustrial and historical atmospheric CO 2 concentrations so that we can separately analyze trends in the natural and anthropogenic CO 2 fluxes. We find that the Southern Ocean (&lt;35°S) CO 2 sink has weakened by 0.1 Pg C a À1 from 1979-2004, relative to the expected sink from rising atmospheric CO 2 and fixed physical climate. Although the magnitude of this trend is in agreement with prior studie

Precision medicine and adverse drug reactions related to cardiovascular drugs

Cardiovascular disease remains the leading global cause of death. Early intervention, with lifestyle advice alongside appropriate medical therapies, is fundamental to reduce patient mortality among high-risk individuals. For those who live with the daily challenges of cardiovascular disease, pharmacological management aims to relieve symptoms and prevent disease progression. Despite best efforts, prescription drugs are not without their adverse effects, which can cause significant patient morbidity and consequential economic burden for healthcare systems. Patients with cardiovascular diseases are often among the most vulnerable to adverse drug reactions due to multiple co-morbidities and advanced age. Examining a patient’s genome to assess for variants that may alter drug efficacy and susceptibility to adverse reactions underpins pharmacogenomics. This strategy is increasingly being implemented in clinical cardiology to tailor patient therapies. The identification of specific variants associated with adverse drug effects aims to predict those at greatest risk of harm, allowing alternative therapies to be given. This review will explore current guidance available for pharmacogenomic-based prescribing as well as exploring the potential implementation of genetic risk scores to tailor treatment. The benefits of large databases and electronic health records will be discussed to help facilitate the integration of pharmacogenomics into primary care, the heartland of prescribing