The Indian Ocean Dipole as an indicator of climatic conditions affecting European birds

Abstract

Variation in large-scale climatic conditions can have profound effects on local weather patterns and ecological processes. For example, it is well known that a positive shift in the North Atlantic Oscillation (NAO) during the last 2 decades has coincided with warmer, wetter winters over Northern Europe and advances in spring phenology, including both migration and breeding of birds. However, the effect of the NAO is not evident throughout the Northern Hemi- sphere and the same is true of the El Nino-Southern Oscillation (ENSO), which has been linked to survival of northern birds wintering in Africa. Recently, a growing body of evidence suggests that an independent ocean circulation system in the Indian Ocean, the Indian Ocean Dipole (IOD), is partly responsible for driving climate variability in the surrounding landmasses. The IOD had traditionally been viewed as an artefact of the ENSO system, although increasingly evidence is accruing that it is a separate and distinct phenomenon. Here we present some results on the causes of the IOD, how it develops within the Indian Ocean, its relationships with the ENSO, and the consequences for East African climate dynamics and associated impacts on ecosystems, in par- ticular along the Eastern Arc Mountains of Kenya and Tanzania. In this opinion article we evalu- ate current research initiatives focused on characterizing the IOD, and examine how effective these will be in determining climate change impacts on East African ecosystems, particularly with respect to avian lifecycles.