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 Hemisphere and the same is true of the El Niño-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 particular along the Eastern Arc Mountains of Kenya and Tanzania. In this opinion article we evaluate 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.

Peer Review #2 of "Climatic variation in Africa and Europe has combined effects on timing of spring migration in a long-distance migrant Willow Warbler Phylloscopus trochilus (v0.2)"

“…This supports the suggestion by Tryjanowski et al (2013) that the IOD is an important indicator of climate conditions which influence birds breeding in Europe. Red-breasted Flycatchers Ficedula parva arrived early in spring in Białowieża Forest, eastern Poland, in years with a high November-March IOD (Mitrus, Sparks & Tryjanowski, 2005;Tryjanowski, Stenseth & Matysioková, 2013). We found a similar relationship between Willow Warblers' arrivals and August-October IOD (Fig.…”

“…Stenseth et al, 2003;MacMynowski & Root, 2007;Miller-Rushing et al, 2008), as has the Indian Ocean Dipole (IOD) (e.g. Hušek et al, 2008;Zduniak et al, 2010;Tryjanowski, Stenseth & Matysioková, 2013;Tobolka et al, 2018). The PeerJ reviewing PDF | (2019:10:41859:2:1:NEW 17 Feb 2020)…”

Climatic variation in Africa and Europe has combined effects on timing of spring migration in a long-distance migrant Willow WarblerPhylloscopus trochilus

“…Few studies have used the Sahel Precipitation Anomaly (SAH) (e.g., Zwarts et al, 2009;Tobolka et al, 2018) as a proxy for rainfall in the Sahel, where many European migrants stop over or stay for winter. The relationship between the timing of migration and the El-Niño-Southern Oscillation (ENSO/SOI) has been marginally explored (e.g., Stenseth et al, 2003;MacMynowski & Root, 2007;Miller-Rushing et al, 2008), as has the Indian Ocean Dipole (IOD) (e.g., Hušek et al, 2008;Zduniak et al, 2010;Tryjanowski, Stenseth & Matysioková, 2013;Tobolka et al, 2018). The SOI and IOD are continental-scale weather anomalies which are correlated with rainfall and temperatures in the southern hemisphere (Black, 2005;Marchant et al, 2006), thus they might serve as useful indices that reflect the conditions which migrant European birds experience in eastern and southern Africa.…”

Challenging a 15‐year‐old claim: The North Atlantic Oscillation index as a predictor of spring migration phenology of birds

“…The North Atlantic Oscillation (NAO) is one of the climatic variables, along with temperature, precipitation, and wind conditions, that have been most often investigated as a predictor of spring migration phenology. The NAO is a large‐scale fluctuation in atmospheric sea‐level pressure difference between the subtropical North Atlantic region (centred on the Azores) and the subpolar region (centred on Iceland) (Gordo, Barriocanal, & Robson, ; Tryjanowski, Stenseth, & Matysioková, ). The NAO is known to affect (i) the mean wind speed and direction of winds across the North Atlantic from North America to Europe; (ii) the heat and moisture transport between the Atlantic and the surrounding continents; (iii) the intensity, paths, and number of storms in the area; and (iv) sea surface temperature and currents (Hurrell, ; Hurrell, Kushnir, Ottersen, & Visbeck, ).…”

“…Hüppop & Hüppop, ; Rubolini et al., ), or even to have a marked effect (e.g. Forchhammer, Post, & Stenseth, ; Lehikoinen, Sparks, & Žalakevičius, ; Rainio, Laaksonen, Ahola, Vähätalo, & Lehikoinen, ; Tryjanowski et al., ; Žalakevičius, Bartkevičien≐, Ivanauskas, & Nedzinskas, ) on spring migration timing of birds. Yet, the results reported in the literature strongly vary, ranging from no correlation to very strong correlations, including contrasting directions of the effect of the NAO on spring migration timing, for example, advancement of spring arrival in northern Europe vs. delay in southern Europe during years of high NAO (winter) index values (Jonzén et al., ).…”