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Review&Forecast—January 2010 Issue

CLIVAR Makes Strides in Ocean-Climate Research

By Howard Cattle
International Climate Variability and Predictability Project Office

Within the World Climate Research Programme (WCRP), sponsored by the World Meteorological Organization, the International Council for Science and the Intergovernmental Oceanographic Commission for the U.N. Educational, Scientific and Cultural Organization, the International Climate Variability and Predictability (CLIVAR) has particular responsibility for coordinating research on the role of the ocean in climate. Over the past year, CLIVAR has been developing its contributions to the WCRP's implementation plan for 2010 through 2015.

CLIVAR's imperatives for the coming years are to provide contributions in the areas of anthropogenic climate change; decadal variability, predictability and prediction; intraseasonal predictability and prediction; improved atmosphere and ocean components of Earth system models; data synthesis, analysis, reanalysis and uncertainties in predictions; the ocean observing system; and capacity building.

CLIVAR provided input for two major events this past year—World Climate Conference-3 (WCC-3) in Geneva, Switzerland, in September, and the OceanObs'09 conference in Venice, Italy, also in September. A primary outcome of WCC-3 was to establish an international framework to guide the development of climate services and link science-based climate predictions and information with climate risk management and adaptation to climate variability and change throughout the world.

An important question for CLIVAR is how to provide the best initial conditions of the state of the ocean in order to study the predictability of the climate system on decadal timescales. To consider these issues, CLIVAR co-sponsored an international workshop on Earth-system initialization for decadal predictions held in Utrecht, Netherlands, in November. CLIVAR's Global Synthesis and Observations Panel (GSOP) is contributing to this area through the assessment of ocean synthesis/analysis products derived from assimilating the global database of ocean observations into ocean models. Links to ocean synthesis data sets have now been added to CLIVAR's online Ocean Synthesis Directory.

GSOP promotes the global ocean observing system in collaboration with the Ocean Observations Panel for Climate. These two panels and the International Geosphere-Biosphere Programme's Integrated Marine Biogeochemistry and Ecosystem Research project provided the science leadership for the organization of OceanObs'09.

GSOP's activities in the area of ocean observation are complemented by the activities of CLIVAR's four regional ocean basin panels for the Atlantic, Pacific, Indian and Southern oceans. Atlantic panel activities are focused on the tropical Atlantic and the Atlantic meridional overturning circulation (AMOC) in the North and South Atlantic. Tropical Atlantic studies are centered on the Tropical Atlantic Climate Experiment (TACE), the design of which builds on the Prediction and Research Moored Array in the Atlantic (PIRATA). The results of TACE are expected to contribute to the final design of a sustained observing system for the tropical Atlantic and will feed into West African monsoon research. To help with the latter, the panel sponsored a meeting in Toulouse, France, in February that brought together representatives of TACE, PIRATA and the African Monsoon Multidisciplinary Analysis project. The panel also facilitated development of the observing system for the AMOC, sending representatives to key meetings to provide input on how to move forward in both the North and South Atlantic.

CLIVAR's Pacific panel has a strong focus on El Ni'o Southern Oscillation (ENSO) prediction and organized an international workshop on El Ni'o and climate change in association with the Greenhouse 2009 conference in Perth, Australia, in March. A workshop this year will address ENSO and its applications. The panel provides a platform for the coordination of international field programs in the Pacific focused on the ocean and coupled ocean-atmosphere processes. It is also spearheading activities to improve our understanding of the South Pacific Convergence Zone (SPCZ), a band of low-level convergence, cloudiness and precipitation extending from the west Pacific warm pool southeast toward French Polynesia. A workshop on SPCZ dynamics, impacts and future changes is planned for this year.

The Indian Ocean panel provides scientific and technical oversight for implementation of the sustained ocean observing system for the Indian Ocean (IndOOS) and coordinates research on the role of the Indian Ocean in the climate system. IndOOS is a multiplatform long-term observing system consisting of Argo floats, surface drifting buoys, tide gauges, a moored array and voluntary observing system-based expendable bathythermograph/con-ductivity-temperature-depth transects. Satellite measurements provide the backbone for observations of sea surface conditions. IndOOS's critical component is the research moored array for African-Asian-Australian monsoon analysis and prediction, which will consist of 46 moorings in total, with 25 moorings in place at the time of writing. This array, together with the tropical atmosphere-ocean/ triangle transocean buoy network array in the Pacific and the PIRATA array in the Atlantic, will, when complete, give us a global tropical moored buoy network for the first time.

In the Southern Ocean, CLIVAR and others are helping to define and promote a sustained Southern Ocean observing system (SOOS) based on repeat hydrography, enhancement of the Argo array, underway sampling from ships, sea ice observations, remote sensing and, uniquely for this area, animal-borne sensors. The Argo network, which CLIVAR co-sponsors, has dramatically increased hydrographic coverage in the upper 2,000 meters of the water column over the region and has helped to provide evidence for significant warming and freshening. Beneath 2,000 meters, observations of bottom water variations also point to large-scale warming. Despite these recent insights from observations, there remains the need for the more systematic and sustained approach to ocean measurements that will be provided by the SOOS.

Finally, from an ocean modeling perspective, CLIVAR's Working Group on Ocean Model Development is primarily focused on carrying out coordinated ocean and sea ice reference experiments. This means providing ocean model simulations (run with observed surface forcing for the period from 1948 to 2006) and comparing them with observations to assess model performance, leading to an enhanced understanding of how changes in surface forcing affect large-scale ocean processes. The panel led an OceanObs'09 community white paper on problems and prospects in large-scale ocean circulation models and also hosted a workshop on ocean mesoscale eddies at the Met Office in Exeter, England, last April.

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