3 Projects, page 1 of 1
The planet's oceans are absorbing a substantial fraction of the CO2 released by anthropogenic fossil fuel and biomass burning. As a consequence the pH of seawater is dropping; a process called ocean acidification. The concern is that these changes will have a profound impact on marine biota by affecting both species range of habitat and the calcification of their skeletons and shells. At the current rate of CO2 uptake, the average surface ocean pH will be lower than that experienced by marine organisms at any time over the last several million years. The most vulnerable ecosystems are in the polar regions and hence we will focus on the northern North Atlantic. Here seawater is corrosive to carbonate minerals and so organisms that calcify in these waters will be particularly sensitive to any acidification. We have selected representative groups of marine plankton that live at the surface in the top metres of the ocean (foraminifers and coccolithophores) and hence in habitats already altered by the 0.1 pH drop since the start of the industrial period in the late 19th Century. Foraminifers and coccolithophores are single-celled organisms. We have selected these groups because they are 1) key carbonate producers and hence contribute to global carbon cycle, and 2) significant components of the planktic ecosystem. How can we test if the seawater pH and carbonate ion changes over the last 150 years have influenced organisms with carbonate skeletons? Changes have already been suggested in the scientific literature for these calcifiers and so it is important to test these results using a larger number of species and different groups of organisms at the same location to assess possible ecosystem impacts. The project will focus on high resolution sediment cores which will allow us to study marine plankton at decadal resolution. We will be able to determine both, natural variability within these ecosystems over the last 1000 years and quantify OA changes over the last 150 years. We will compare and contrast foraminifers and coccolithophores. We are expecting possible differences as the former are zooplankton, live much longer before reproducing and encapsulate sea water to calcify. The contrast, the latter are phytoplankton and hence calcification and photosynthesis will be influenced by the changes in surface water chemistry, they divide daily instead of bi-weekly to monthly and they calcify in an internal vesicle. Changes in calcification will be determined for both groups, determining their weight (just foraminifers) and thickness. As foraminifers grow by adding chambers, we can analyse the entire life history and see if possible changes in size are related to changes in timing of development. We has, using detailed scanning electron analysis and morphometics, determine these changes not just for the traditional 'geological species' but for more subtle 'morphotypes' which have been recognised to have specific environmental adaptation and potentially different reactions to OA. All of this work will be done in a framework of well dated material, analysed for sedimentological alterations (winnowing) to ascertain the comparability of the results. Environmental information will additionally help to interpret the data. These results will determine if the base of the marine food chain and the major contributors to the global carbon cycle, have already altered their calcification due to ocean acidification. All this information is needed to improve predictions of how vulnerable marine ecosystems are to ocean acidification, how likely they are able to adapt and support effective advice to policy makers and managers of marine bioresources on the possible size and timescale of risks of ocean acidification to marine ecosystems.
The burning of fossil fuels is releasing vast quantities of extra carbon dioxide to the Earth's atmosphere. Much of this stays in the atmosphere, raising CO2 levels, but much also leaves the atmosphere after a time, either to become sequestered in trees and plants, or else to become absorbed in the oceans. CO2 staying in the atmosphere is a greenhouse gas, causing global warming; CO2 entering the sea makes it more acidic, and the ongoing acidification of seawater is seen in observational records at various sites where time-series data are collected. The changing chemistry of seawater due to ocean acidification is mostly well understood and not subject to debate. What is much less well known is the impact that the changing chemistry will have on marine organisms and ecosystems, on biogeochemical cycling in the sea, and on how the sea interacts with the atmosphere to influence climate. We will look to investigate these questions in terms of how the surface waters of the world's oceans, and the life within, will respond to ocean acidification. Most of what we know about biological impacts, and the source of the current concern about the impact on marine life, comes from experimental studies in which individual organisms (e.g. single corals) or mono-specific populations (e.g. plankton cultures) have been subjected to elevated CO2 (and the associated lower pH) in laboratory experiments. These laboratory experiments have the advantage of being performed under controlled conditions in which everything can be kept constant except for changes to CO2. So if a response is observed, then the cause is clear. However, there are also limitations to laboratory studies. For instance, organisms have no time to adapt evolutionarily, and there is no possibility of shifts in species composition away from more sensitive forms towards more acid-tolerant forms, as might be expected to occur in nature. Another shortcoming is the absence of food-web complexity in most experiments, and therefore the absence of competition, predation, and other interactions that determine the viability of organisms in the natural environment. We seek to advance the study of ocean acidification by collecting more observations of naturally-occurring ecosystems in places where the chemistry of seawater is naturally more acidic, and/or where it naturally holds more carbon,as well as locations which are not so acidic, and/or hold more usual amounts of carbon. By contrasting the two sets of observations, we will gain an improved understanding of how acidification affects organisms living in their natural environment, after assemblage reassortments and evolutionary adaptation have had time to play out. Most of the planned work will be carried out on 3 cruises to places with strong gradients in seawater carbon and pH: to the Arctic Ocean, around the British Isles, and to the Southern Ocean. As well a making observations we will also conduct a large number of experiments, in which we will bring volumes of natural seawater from the ocean surface into containers on the deck of the ship, together with whatever life is contained within, and there subject them to higher CO2 and other stressors. We will monitor the changes that take place to these natural plankton communities (including to biogeochemical and climate-related processes) as the seawater is made more acidic. A major strength of such studies is the inclusion of natural environmental variability and complexity that is difficult or impossible to capture in laboratory experiments. Thus, the responses measured during these experiments on the naturally-occurring community may represent more accurately the future response of the surface ocean to ocean acidification. In order to carry out this experimental/observational work programme we have assembled a strong UK-wide team with an extensive track record of successfully carrying out sea-going scientificresearch projects of this type.
Monsoon systems influence the water supply and livelihoods of over half of the world. Observations are too short to provide estimates of monsoon variability on the multi-year timescale relevant to the future or to identify the causes of change on this timescale. The credibility of future projections of monsoon behavior is limited by the large spread in the simulated magnitude of precipitation changes. Past climates provide an opportunity to overcome these problems. This project will use annually-resolved palaeoenvironmental records of climate variability over the past 6000 years from corals, molluscs, speleothems and tree rings, together with global climate-model simulations and high-resolution simulations of the Indian, African, East Asia and South American monsoons, to provide a better understanding of monsoon dynamics and interannual to multidecadal variability (IM). We will use the millennium before the pre-industrial era (850-1850 CE) as the reference climate and compare this with simulations of the mid- Holocene (MH, 6000 years ago) and transient simulations from 6000 year ago to ca 850 CE. We will provide a quantitative and comprehensive assessment of what aspects of monsoon variability are adequately represented by current models, using environmental modelling to simulate the observations. By linking modelling of past climates and future projections, we will assess the credibility of these projections and the likelihood of extreme events at decadal time scales. The project is organized around four themes: (1) the impact of external forcing and extratropical climates on intertropical convergence and the hydrological cycle in the tropics; (2) characterization of IM variability to determine the extent to which the stochastic component is modulated by external forcing or changes in mean climate; (3) the influence of local (vegetation, dust) and remote factors on the duration, intensity and pattern of the Indian, African and South American monsoons; and (4) the identification of palaeo-constraints that can be used to assess the reliability of future monsoon evolution.