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WP6 Climate change & response of deep-sea biota

WP leader: Heiko Pälike NOC, UK
Ralph Schneider, Univ. Kiel, Germany

The IPCC fourth Assessment Report documents evidence from a wide range of species and communities that recent environmental changes are strongly affecting natural biological systems world-wide, including the deep oceans. Many observed changes in phenology and distribution of marine species have been linked to increasing water temperatures, and to other climate-driven changes in ice cover, salinity, oxygen levels, circulation, as well as increased atmospheric and dissolved levels of CO2. Observations since 1961 show that the average temperature of the global ocean has increased to depths of at least 3000 m and that the ocean has been absorbing more than 80% of the heat added to the climate system.

Geological records indicate that ecosystems have some capacity to adapt naturally to climate change, however, this ability to adapt can be exceeded by 2100 by a combination of change in climate and associated disturbance, including ocean acidification. Ecosystems are very likely to be exposed to atmospheric CO2 levels much higher than in the past 650,000 years, and global mean temperatures at least as high as those in the past 740,000 years. By 2100, ocean pH is very likely to be lower than during the last 20 million years.

Beyond ice-core records, the deep seafloor constitutes the longest and least disturbed archive for past climatic, palaeontological, palaeoceanographic and biogeochemical data, stored in sedimentary deposits at up to multi-annual temporal resolution and a wide stratigraphic range, making it a primary target for ocean drilling. An internationally co-ordinated effort to study marine palaeoclimatology and its effect on biota provides the opportunity to gain access to records over timescales that extend the short instrumental period, across the onset of anthropogenic perturbations and beyond. Palaeoclimatic profiles from deep-sea sediments therefore enable investigation of the Earth’s climate, dynamics, and interaction with biological systems over a wide range of timescales. Oceanic records have revealed the magnitude of climate change over the last 100 Ma, the sensitivity of climate to external forcing, the internal instability of global climate leading to abrupt changes as well as the environmental consequences of these changes. However the mechanisms that drive or amplify these changes remain poorly understood and present some of the foremost scientific challenges of our time, requiring international co-ordination to tackle these problems of societal relevance.

Ocean and sub-seafloor sampling, for example through the successful IMAGES and IODP efforts (see WP7 below), have provided insights into several key processes that have allowed us to investigate Climate Change and Evolution of Deep Sea Biota. These records document the extent, rate-of-change and feedback of past climatic changes with biota, in a wide variety of different boundary conditions, therefore sharpening our ability to model them. These records have revealed examples of how past extreme events, apparently driven by massive perturbations in the carbon cycle, may provide additional information on the impact of such forcing on global climate. During the last glacial cycle jumps between warmer and colder states occurred within decades, and have been ascribed to changes in ocean circulation. Through the development of new proxy methods, it is now possible to estimate the past temperature and salinity structure of the oceans, continental ice volumes, nutrient concentrations, biological productivity, rapid sea-level changes and ocean acidity. In terms of ocean biogeochemistry and the carbon cycle, one outstanding unresolved problem is what regulates the concentration of carbon dioxide in the atmosphere. A coupled problem is what limits biological productivity in the marine environment.

In the last couple of years, studies based on molecular analyses of ancient genetic material have provided new insights on paleoecosystem trends. Owing to the higher resolution of DNA sequences as compared to other marker molecules, molecular characterisation of ancient genetic material may improve reconstruction of past communities and related paleoenvironments. Extracellular DNA in deep-sea sediments is by far the largest reservoir of DNA of the world oceans. Extracellular DNA production and accumulation in marine sediments represents a record of processes occurring in the pelagic (through DNA supply attached to sinking particles) and benthic (through in situ extracellular DNA production) domains at different temporal scales. Therefore the analyses of structural and functional genes preserved in the extracellular DNA pool might provide new information about the biodiversity and functioning of present-day ecosystems and paleo-ecosystems. However, the extent to which DNA is preserved under different marine settings, the factors that influence the survival of DNA, and the fidelity of the resulting sedimentary records remain largely unknown. The network activities would provide for the first time an overview of which type of marine settings might be archives of ancient DNA that carry important paleo-environmental and paleoclimatological information. This survey will thus help paleoclimatologists to predict in which marine settings ancient DNA is preserved, and may constitute an archive of paleoenvironmental information to be used for a better definition of climate trends occurring around European continental margins and deep basins. The application of advances in genetics to extent marine species and the development of biomarker molecular proxies in marine sediments are providing critical new dimensions to the study of biogeochemical interactions in the Earth system. However what ultimately limits biological productivity in both modern and past environments is still a major unresolved problem, and requires new cross-disciplinary and internationally co-ordinated ocean sampling and drilling activity, incorporating expertise ranging from ecosystem specialists, geologists, geophysicists, climatologists, meteorologists, biologists and palaeoceanographers.

The IPCC summary of research findings indicates that average Arctic temperatures increased at almost twice the global average rate in the past 100 years. The Polar Regions are highly sensitive to climate change and the instability of the major ice sheets may contribute to rapid changes in ocean circulation, climate and sea-level. Recent internationally co-ordinated sampling of the Arctic sub-seafloor has resulted in the first high-resolution, long-term palaeoceanographic records from this area, chiefly through the European-led contributions to mission-specific platforms of IODP and through the European IPY activities (see WP7). Further research co-ordination is required to augment and fully investigate the implications from these new records. It is necessary to understand how processes in the high Arctic relate to the rapid climate changes associated with deglaciation and the even shorter timescale Dansgaard-Oeschger events in which warming episodes occurred over only a few decades, and what impact these climatic changes had on surface and deep biota (see WP5). Drilling near the Antarctic is essential to monitor the onset of growth of the Antarctic ice sheet and its subsequent behaviour and response to ocean water warming. Research into the response and adaptation of the subsurface and deep ocean to rapid climate changes is developing, and information on the magnitude, speed and regional to basin- wide pattern of deep-sea changes are currently sparse. In a few ongoing tri- and bilateral national research programs, for example on the thermohaline circulation overturning in the North Atlantic (RAPID), or within the ESF EUROCORES programs EUROCLIMATES and EUROMARC, concerted efforts in deep ocean climate research have matured to a point where timely advancement and attainment of their full potential requires further coordinated, multidisciplinary, collaborative investigation and mobilisation of large shore- based and seagoing infrastructure at a European level.

In Europe several marine research institutions and universities have established excellent teams or centres for climate and paleoclimate research in the ocean (e.g., AWI, BCCR, CEREGE, IFM-GEOMAR, ISMAR, LSCE, MARUM, NOCS and the universities of Amsterdam, Barcelona, Bremen, Cambridge, Cardiff, Kiel, Salamanca and Utrecht), that possess an extensive record of well-established co-operation in former pan-European research projects and joint educational programs at the junior researcher level. Based on this platform and involving key cross-disciplinary scientists This WP will develop a core discussion group to specify the most prominent key questions for an overarching European research plan, and will aim to develop strategies for joint utilisation and financing of existing and new shore-based and seagoing technology and infrastructure for probing the sedimentary palaeoclimate and crustal microbiological archive.

List of tentative WP6 participants (Level 3)

F. Abrantes, INETI, Portugal (Palaeoproductivity, micropalaeontology); C. Agnini, Univ. Padova, Italy (Micropalaeontological env. reconstruction); G. Henderson, Univ. Oxford, UK (Geochemical proxies); G. Haug, ETH Zurich, Switzerland (Holocene and Quaternary env. reconstruction); A. Dell’Anno, CONISMA, Italy (DNA research, viruses); J.A. Flores, Univ. Salamanca, Spain (Plankton paleobiodiversity and -ecology); H. Brinkhuis, Univ. Utrecht, Netherlands (Cenozoic climate, dinoflagellates, Arctic); U. Ninnemann, Univ. Bergen, Norway (Southern Ocean Paleoceanography); I. Cacho, Univ. Barcelona, Spain (Paleoceanography); A. Rickaby, Univ. Oxford, UK (Trace metal geochemistry, biogeochemistry); F. Bassinot, LSCE, France (Palaeoceanography); M. Schulz, MARUM, Germany (Climate Modelling); R. Zahn, Univ. Barcelona, Spain (Deep-Ocean Paleocirculation); K. Darling, Univ. Edinburgh, UK (genetics of foraminifera); U. Röhl, MARUM, Germany (Cyclostratigraphy); E. Rohling, NOCS, UK (Rapid sea-level change); A. Mackensen, AWI Bremerhaven, Germany (Biogeochemical cycles); M.-A. Sicre, LSCE, France (Sea-ice reconstructions); S. Barker, Univ. Cardiff, UK (Plankton response to ocean acidification state); T. Stocker, Univ. Bern, Switzerland (Climate Modelling).