Decadal Prediction Over the Americas: Atlantic vs Pacific Processes

The relationship between sea surface temperatures (SST) and North American hydroclimate (NAH) has been the subject of much research in the past decade. Independent research and coordinated efforts such as the US CLIVAR Drought Working Group have shown in idealized experiments that low frequency internal modes of sea surface temperature variability in the Atlantic and Pacific oceans interact and influence persistent droughts and pluvials over portions of North America. Concurrently, climate modelers have recognized that accurate predictions of near term (10-30 year) climate change will require accurate simulation of these internal modes of variability in addition the committed warming and greenhouse gas forcing. Appropriately, a major component of the upcoming-coupled model inter-comparison (CMIP5) for the fifth assessment report to the IPCC will be decadal climate predictions to assess the ability of climate models to capture and simulate near term climate change. The decadal predictions will give insight into the combined effects of internal variability in the oceans and the external forcing on the potential predictability of near term climate variability, but the relative contributions of individual basins remains untested in the coupled model framework. The proposed work seeks to identify the individual contributions of internal and forced climate variability to the potential predictability of Pacific and Atlantic variability, and the relative influence of these basins on NAH. Our hypothesis is that observed NAH is driven by complimentary processes in the Pacific and North Atlantic and is predictable beyond lead times of one year. To test this we propose three main objectives: 

Objective 1: Assess the potential predictability of the observed natural Atlantic and Pacific variability separately and quantify the influence of inter-basin interactions and external forcing on variability in each basin. 

Objective 2: Assess the potential predictability of observed North American hydroclimate and identify the relative influence of natural variability in the Pacific and Atlantic and the GHG forcing. 

Objective 3: Perform a thorough diagnostic study of the CMIP5 control, 20th Century, and near term climate projections to determine the ability of dynamical models to simulate observed decadal SST variability and predict North American hydroclimate with a focus on Pacific versus Atlantic processes.