Martin Visbeck

On the possible long-term fate of oil released in the Deepwater Horizon incident, estimated using ensembles of dye release simulations

We have conducted an ensemble of 20 simulations using a high resolution global ocean model in which dye was continuously injected at the site of the Deepwater Horizon drilling rig for two months. We then extended these simulations for another four months to track the dispersal of the dye in the model. We have also performed five simulations in which dye was continuously injected at the site of the spill for four months and then run them out to one year from the initial spill date. The experiments can elucidate the approximate timescales and space scales of dispersal of polluted waters and also give a quantitative estimate of the dilution rate. Given the uncertainty in rates of chemical or biological degradation for oil or an oil–dispersant mixture, we do not include a decay term for the dye. Thus, these results should be considered an absolute upper bound on the possible spatial extent of the dispersal of oil or oil–dispersant mixture. n n The model results indicate that it is likely that oil-polluted waters from the Deepwater Horizon incident will, at some time over the six months following the initial spill date, be transported at relatively low concentrations over a significant part of the North-West Atlantic Ocean. However, this does not imply that oil will reach the eastern shores of North America, or that it will even be detectable. We present probabilities for the transport timescales and estimates of ensemble mean arrival times, and we briefly discuss the likely dispersion timescales and pathways of dye released in the subsurface ocean.

Anomalous mid-twentieth century atmospheric circulation change over the South Atlantic compared to the last 6000 years

Determining the timing and impact of anthropogenic climate change in data-sparse regions is a considerable challenge. Arguably, nowhere is this more difficult than the Antarctic Peninsula and the subantarctic South Atlantic where observational records are relatively short but where high rates of warming have been experienced since records began. Here we interrogate recently developed monthly-resolved observational datasets from the Falkland Islands and South Georgia, and extend the records back using climate-sensitive peat growth over the past 6000 years. Investigating the subantarctic climate data with ERA-Interim and Twentieth Century Reanalysis, we find that a stepped increase in precipitation across the 1940s is related to a change in synoptic atmospheric circulation: a westward migration of quasi-permanent positive pressure anomalies in the South Atlantic has brought the subantarctic islands under the increased influence of meridional airflow associated with the Amundsen Sea Low. Analysis of three comprehensively multi-dated (using 14C and 137Cs) peat sequences across the two islands demonstrates unprecedented growth rates since the mid-twentieth century relative to the last 6000 years. Comparison to observational and reconstructed sea surface temperatures suggests this change is linked to a warming tropical Pacific Ocean. Our results imply modern South Atlantic atmospheric circulation has not been under this configuration for millennia.

Ocean science research is key for a sustainable future

Human activity has already affected all parts of the ocean, with pollution increasing and fish-stocks plummeting. The UN’s recent announcement of a Decade of Ocean Science provides a glimmer of hope, but scientists will need to work closely with decision-makers and society at large to get the ocean back on track.

How healthy is the human-ocean system?

Halpern et al (2012 An index to assess the health and benefits of the global ocean Nature 488 11397)propose a detailed measure of the state of the human-ocean system against ten societal goals. They devote less attention to the normative foundation of the index, which is crucial for assessing the overall health of the human-ocean system, notably when it comes to aggregation of potentially conflicting goals. Social choice theory provides several possible functional forms for assessing the compound change in various goals. The one chosen by Halpern et al, the arithmetical mean, is not nonly a specific but also an extreme case. It implicitly allows for unlimited substitution. A one-unit reduction in one goal can be fully offset by a one-unit increase in another with the same weighting factor. For that reason, the current index satisfies an extremely weak sustainability concept. We show that the results in Halpern et al are not robust when one adopts a strong sustainability concept. The noverall health score of the ocean decreases, the ranking of the various coastal states changes substantially, and the assessment of sustainable development needs to be partially reversed.

Aspects of acoustic transponder surveys and acoustic navigation

New off-the-shelf hardware has allowed improved techniques for acoustic transponder deployment and surveying, saving time and improving the accuracy of results. In particular, affordable acoustic deck units which allow continuous computer sampling of acoustic ranges while the ship is under way (merged with simultaneous GPS position data), allow application of a variety of survey techniques, to determine the exact transponder positions or separations. Apart from a particular hardware setup used, various possible analysis techniques are summarized and results compared from a number of applications. In addition, the positioning problem using 2 or 3 acoustic transponders is discussed. The solutions are presented together with their respective errors, allowing simple rule-of-thumb estimates for positioning (or velocity) accuracy, as a function of the uncertainty in input parameters (e.g. transponder positions, acoustic travel time, depth measurement).

Mapping interactions between the sustainable development goals: lessons learned and ways forward

Pursuing integrated research and decision-making to advance action on the sustainable development goals (SDGs) fundamentally depends on understanding interactions between the SDGs, both negative ones (“trade-offs”) and positive ones (“co-benefits”). This quest, triggered by the 2030 Agenda, has however pointed to a gap in current research and policy analysis regarding how to think systematically about interactions across the SDGs. This paper synthesizes experiences and insights from the application of a new conceptual framework for mapping and assessing SDG interactions using a defined typology and characterization approach. Drawing on results from a major international research study applied to the SDGs on health, energy and the ocean, it analyses how interactions depend on key factors such as geographical context, resource endowments, time horizon and governance. The paper discusses the future potential, barriers and opportunities for applying the approach in scientific research, in policy making and in bridging the two through a global SDG Interactions Knowledge Platform as a key mechanism for assembling, systematizing and aggregating knowledge on interactions.

Indicators for monitoring sustainable development goals: An application to oceanic development in the European Union: OCEAN SDG

The 2030 Agenda for Sustainable Development that includes a set of 17 Sustainable Development Goals (SDG) with 169 specific targets could be a step forward in achieving efficient governance and policies for global sustainable development. An essential element will be the global indicator framework for monitoring and assessing progress over and against both the overall goals and the specific targets and to guide policy towards sustainable solutions. In the debate over the current indicator framework, little attention is devoted to conceptual issues. Here, we argue that the inclusion of composite indicators, which can be used to aggregate individual indicators, as complements to the single indicators could support the overall assessment process without necessitating any significant changes to the currently proposed indicator base. While the individual indicators remain the backbone of the indicator framework, serving the purpose for detailed assessment of specific policy measures, the composite indicators allow for an explicit assessment of trade-offs between policies. Our illustrative investigation of the sustainable oceanic development of EU coastal states highlights how much a comprehensive assessment can benefit from the additional inclusion of composite indicators.