January 2013 Issue
Climate Studies of Ocean-Atmosphere Interactions Get New Focus
By Roger Barry
Antonio C. Caltabiano,
International CLIVAR Project Office, National Oceanography Centre
The World Climate Research Programme (WCRP) is redefining its scientific research directions. Key science topics have been identified,which will set the research agenda for international climate science over the coming years.
WCRP's project on ocean-atmosphere interactions, CLIVAR (Climate Variability and Predictability), has contributed to these discussions and responded with a new set of its own challenges, which will contribute to WCRP science. These challenges are: intraseasonal, seasonal and interannual variability and predictability of monsoon systems; decadal variability and predictability of ocean and climate variability; trends, nonlinearities and extreme events; marine biophysical interactions and dynamics of upwelling systems; and the dynamics of regional sea level variability.
Ocean observations are a crucial component of CLIVAR science, driven and implemented by CLIVAR's scientific panels and working groups, in collaboration with the wider community.
In the Pacific region, both the Northwestern and Southwest Pacific Ocean Circulation and Climate Experiments (NPOCE and SPICE, respectively) are examples of projects studying changes in water properties and ocean circulation in the Pacific Ocean's western boundary currents, a region spanning from Australia to Japan. This region is important because of the role it plays in modulating East Asian monsoon variations and cyclone development in the Pacific.
In the Atlantic, CLIVAR scientists are looking at how the tropical ocean affects continental precipitation over the Amazon and West Africa. Scientists have difficulty representing sea surface temperatures of coastal upwelling zones correctly in climate models; required observations are planned to deal with this issue. Improved predictions of equatorial Atlantic sea surface temperatures are vital for predicting the onset and variability of the West African monsoon.
The Intra-Americas Study of Climate Processes (IASCLIP) aims to improve and expand the observational network across the region in order to improve understanding of the seasonal cycle and movement of the intertropical convergence zone. This aids understanding of the transition of the monsoon systems between South and North America.
Ocean and Climate
The Southern Ocean is a particularly remote, hostile region. Despite its global significance as a connector of major ocean basins and a modulator of climate, sea level, biogeochemical cycles and biological productivity, it has historically been sparsely observed. However, recent advancements in ocean-observing technologies have provided the means to monitor this region.
CLIVAR has been instrumental in developing the Southern Ocean Observing System, which will employ an array of technologies to deliver the data required to address these challenges, such as underway sampling from ships, animal-borne sensors and remote sensing. Commitments include reoccupation of hydrographic lines through the Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP); monitoring of the Drake Passage using full-depth hydrography and moored instruments, including continuation of the long-term bottom pressure recorder deployments and tide-gauge observations; moored arrays in the Weddell Sea and other locations; and biological measurements from ships of opportunity.
While this is encouraging, there is substantial work to be done to secure the resources for a sustained and comprehensive observing system in the Southern Ocean. Programs such as the Argo profiling float array and the Marine Mammals Exploring the Oceans Pole to Pole (MEOP) network of tagged seals have helped to revolutionize observation of the Southern Ocean. However, there is as yet no firm commitment to long-term sustained funding of these systems.
CLIVAR is also involved in the coordination of several large projects that focus on the Atlantic Ocean and the emerging field of decadal prediction. These include Germany's MiKlip (Mittelfristige Klimaprognosen, Decadal Climate Prediction) and three European Union programs: Thermohaline Overturning ' at Risk? (THOR), the Comprehensive Modeling of the Earth System for Better Climate Prediction and Projection (COMBINE) and the North Atlantic Climate (NACLIM).
CLIVAR is also involved in measuring and monitoring the Atlantic Meridional Overturning Circulation (AMOC), which involves the U.K. Natural Environment Research Council's Rapid Climate Change program (UK-RAPID) and South Atlantic Meridional Overturning Circulation projects. CLIVAR identifies gaps and possible improvements in the observing systems, and advocates the implementation of a sustained network for AMOC.
Trends, Nonlinearities and Extreme Events
CLIVAR, along with its sister WCRP project: Global Energy and Water Cycle Experiment (GEWEX), is involved in a number of activities on drought. One substantial effort is the development of a global drought information system that builds upon worldwide investments in drought monitoring, risk management and research, and climate-prediction capabilities.
To improve understanding and prediction of major weather events and climate extremes within the intra-Americas region, IASCLIP is studying tropical cyclone frequency, intensity and point of landfall; flood events; and regional drought.
Marine Biophysical Interactions, Upwelling Systems
Measurements of components of the biogeochemical cycle are key in order to address the long-term impact on local ecosystems and fisheries. Historically CLIVAR has maintained strong links with the North Pacific Marine Science Organization and the Integrated Marine Biogeochemistry and Ecosystem Research (IMBER) project.
In the Indian Ocean, CLIVAR has established a partnership between the Indian Ocean Observing System and IMBER's Sustained Indian Ocean Biogeochemical and Ecological Research (SIBER) initiative. This collaboration will provide a blueprint for scientific study of biogeochemical cycles, ecosystem dynamics and their interactions in the Indian Ocean. These groups now plan to implement a joint project, Eastern Indian Ocean Upwelling: Dynamics and Ecosystem.
The CLIVAR-endorsed Tropical Atlantic Climate Experiment (TACE) has a strong relationship with the German SFB 754 research project, which addresses climate-biogeochemistry interactions in the tropical oceans, with a focus on ocean deoxygenation and tropical oxygen minimum zones in the Atlantic and Pacific, and implications for the global marine biogeochemical system.
Dynamics of Regional Sea Level Variability
As a relatively new program focus for CLIVAR, activities aimed at understanding and predicting the dynamics of regional sea level variability are under development. One such activity will bring together leading international scientists and early-career researchers from the ocean, ice-sheet, ice-shelf, and sea level rise modeling and observational communities.
The aim is to improve projections of future sea level, which will inform knowledge of potential coastal impacts and contribute to the understanding of a topic drawing intense scientific and societal interest.