Teleconnections are interactions between different parts of the atmosphere (e.g. high latitudes and low latitudes). Teleconnections play an integral part in the study of air-sea interactions and global climate processes. They are often the missing piece in the puzzle of the environment's primary spatial and temporal pattern across the globe.

Currently underway are several projects that deal with teleconnections. One project supported by PFEL base funds seeks to develop climate indicies for research on salmon variability. The Southern Oscillation Index (SOI) has been shown to be well correlated with interannual to decadal variability in the NEP (e.g., Pulwarthy and Redmond 1998, Mantua et al. 1998). We have developed and are testing two new indices that describe variability in the teleconnection between tropical and extratropical regions. The NOI (extratropical Northern Oscillation Index) and SOI* (extratropical Southern Oscillation Index) series are supplements to the commonly used SOI as indices of large-scale climate variability. Research on these climate indicies is continuing as a joint PFEL-Globec NEP supported activity.

The Extratropical Northern Oscillation Index

Our studies of annual cycles and EN and LN events have shown that the North Pacific High (NPH) is an important indicator of climate variability in the NEP. On a basin scale, this stems from the NPH's role in the North Pacific's Hadley-Walker circulation which links the NEP to the tropical Pacific and Asia. On a smaller scale, this stems from the NPH's role in governing surface wind stress over much of the NEP.

A strong correlation between the SOI and NPH on interannual to decadal scales (Trenberth and Shea 1987) led us to develop a North Pacific equivalent of the SOI (Schwing and Murphree 1999). The NOI is the SLP anomaly from climatology at the annual mean position of the NPH (35°N 135°W) minus the SLP anomaly at Darwin, Australia. The NOI and SOI are well correlated on interannual and decadal scales (Schwing and Murphree 1999). We are currently testing the NOI's value as an index of NEP climate change, and as a key to identifying the major mechanisms of climate change in the region.

On interannual scales the NOI and SOI are well correlated from 1981-1989 and poorly correlated during 1990-1998 (Schwing and Murphree 1999). This, along with other evidence of a change in EN and LN frequency (Trenberth and Hoar 1996, 1997), suggests that a decadal change may have occurred around 1990 that extended throughout most of the North and South Pacific and into southern and eastern Asia.