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A predictable ocean where society has the capacity to understand current and future ocean conditions

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By Milthon Lujan

Denmark.- ICES working groups on seasonal-to-decadal prediction of marine ecosystem, on impacts of warming on growth rates and fisheries yields, and integrated, physical-biological and ecosystem modelling are all working towards a predicted ocean.

The scientific community’s ability to forecast the state of the ocean is rarely appreciated, but far exceeds that which can be achieved on land or in the atmosphere. Whereas weather forecasts on land stretches to weeks, in the North Atlantic, for example, skillful forecasts can be made seasons, years, and even up to a decade or more into the future. This region, as the most predictable ocean on the planet, therefore has the potential to play a key role in driving the “Predicted Ocean” aspect of the Ocean Decade forward. However, the ability to make predictions of, for example, sea surface temperature, is not sufficient to achieve the goals of the Decade alone or to make positive contributions to the sustainable development of ocean-dependent communities. Decision-makers from both the public and private sectors need information that addresses their specific questions and information requirements. There is a gap between the forecast data that the scientific community currently delivers and the information needed by society to respond to the challenges of oceanic variability and change.

ICES Working Group on Seasonal-to-Decadal Prediction of Marine Ecosystems (WGS2D) aims to bridge this gap by developing and producing forecast products that are relevant to decision makers from all parts of society. This group has developed forecast products relating to the distribution, timing and abundance of key species in the ocean: examples include spatial distribution forecasts of blue whiting for use in monitoring applications, productivity (recruitment) forecasts of sandeel in the North Sea for use in planning commercial activities, and of the timing of Garfish migration, for use by recreational anglers. These products, developed in collaboration with end-users to address specific questions, are being regularly delivered in an operational and transparent manner to support decision-making. By combining marine biological science with climate observation and prediction systems, we have shown that it is possible to make reliable and valuable forecasts of life in the ocean months and years into the future.

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This technology has therefore passed the “proof-of-concept” stage and is already making contributions to the sustainable management, exploitation and monitoring of marine resources in the ICES area. The next steps involve scaling the approach up, and applying it more generally where there is a need: the recent IPCC Special Report on the Oceans identified these types of forecasts as an important tool to “help manage negative impacts from ocean changes”. While the WGS2D forecasts are specific to an individual application, the experience and lessons learned in developing, distributing, using and evaluating these forecasts can be applied generally to realize the full potential of “A Predicted Ocean” to support climate adaptation and sustainable development.

The temperature-size rule (TSR; higher temperatures result in smaller body sizes) is a central tenet of biology with major implications for size-structured marine ecosystems experiencing warming. Synchronous shifts towards smaller body sizes of marine fish have already been detected in the rapidly warming North Sea (Baudron et al. 2014). If warming trends continue, then the TSR, combined with poleward range shifts of fish populations, have the potential for decreasing fisheries yields by ca. 25% (Cheung et al. 2012). Decreasing yields are concerning given that fish provide 3.2 billion people with almost 20 percent of their average per capita intake of animal protein (FAO 2018) and constitute a climate-smart protein source (Parker et al. 2018).

Commercial fish populations are ideally positioned to test whether there is a common trend in growth rates that is consistent with the TSR. Fish stocks inhabit thermal conditions ranging from cold upwelling regions (non-warming) to shallow regional seas experiencing strong warming. Furthermore, length and age have been routinely measured by national fisheries agencies to estimate the vital rates of fish stocks. A coordinated analysis of the existing age/length data can produce robust predictive models for forecasting the effect of temperature on growth rates.

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In 2020, ICES/PICES Working Group on Impacts of Warming on Growth Rates and Fisheries Yields (WGGRAFY) will bring together scientific expertise on fish growth and ecology to test the TSR on a global scale with an aim to develop generic models for ocean prediction. If the signature of warming can be detected in the body size of commercial fish on a global scale, then the impact on fisheries yield and consequences for food security can be more accurately specified, and appropriate adaptation/mitigation plans developed. WGGRAFY will conduct a series of targeted research questions assessing the evidence for warming-induced growth rate change, and then implications of this for fish yields and food security will be addressed. The group will also develop a strategic plan for archiving length-at-age data similar to how ICES currently archive length-at-age data for European waters (DATRAS).

The Working Group on Integrated, Physical-biological and Ecosystem Modelling (WGIPEM) advances the state of the art in coupled physical-biological and ecosystem modelling. An important part of the work is the continued development of end-to-end ecosystem models that incorporate hydrodynamics, lower and higher trophic levels and the link to ecosystem services and human impacts. WGIPEM carries out its modelling work by sharing and discussing simulation results, identifying gaps in knowledge in these modelling activities, and recommending and performing activities to improve model performance. Several of the applied models are already operational and used to give advice to stakeholders and managers, whereas others are mainly used for research purposes. The applied models are considered as useful tools that can support the goals of the UN Decade of Ocean Science by providing scientific knowledge and data and address the societal outcomes, e.g. ‘a predicted ocean’.

The applied models in WGIPEM can be used to integrate scarce observational data points in space and time and provide a more full picture of the current state of the oceans. This applies both to the state of single fish stocks, ecosystem indicators (e.g. nutrient-, Chl a- and oxygen levels) and ecosystem services (e.g. nutrient remediation, food provisioning). Further, the models can increase our understanding of the oceans through quantification of processes that are difficult/impossible to measure, reveal ecosystem functions and complex food web interactions (e.g. trophic cascading effects) and evaluate responses of ecosystem components to bottom-up and top-down pressures from human activities and natural drivers. For predictions of the future ocean, ongoing modelling studies are investigating ecosystem responses to a range of pressures (e.g. climate change, invasive species, fishery, eutrophication, aquaculture, microplastics, etc.) and how these combine (e.g. additively or synergistically) in different future scenarios.

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Source: ICES

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