Western Indian Ocean marine and terrestrial records of climate variability: a review and new concepts on land–ocean interactions since AD 1660

Abstract

We examine the relationship between three tropical and two subtropical western Indian Ocean coral oxygen isotope time series to surface air temperatures (SAT) and rainfall over India, tropical East Africa and southeast Africa. We review established relationships, provide new concepts with regard to distinct rainfall seasons, and mean annual temperatures. Tropical corals are coherent with SAT over western India and East Africa at interannual and multidecadal periodicities. The subtropical corals correlate with Southeast African SAT at periodicities of 16-30 years. The relationship between the coral records and land rainfall is more complex. Running correlations suggest varying strength of interannual teleconnections between the tropical coral oxygen isotope records and rainfall over equatorial East Africa. The relationship with rainfall over India changed in the 1970s. The subtropical oxygen isotope records are coherent with South African rainfall at interdecadal periodicities. Paleoclimatological reconstructions of land rainfall and SAT reveal that the inferred relationships generally hold during the last 350 years. Thus, the Indian Ocean corals prove invaluable for investigating land-ocean interactions during past centuries.

Changes in coral sensitivity to thermal anomalies

“…Possibly the early pre-peak temperature rise in 2016 were driven by ENSO forces, while the later and prolonged warm temperatures in 1998 were influenced by a strong and persistent IOD. Moreover, the complex interactions between these and other oceanographic oscillations, such as the Pacific Decadal Oscillation, are likely to result in complex East African temperature anomalies (Cole et al 2000, Zinke et al 2009). Despite the strong similarity in gross thermal exposures between 1998 and 2016, differences in prebleaching temperature fluctuations probably influenced bleaching responses.…”

Seasonal rainfall variability in southeast Africa during the nineteenth century reconstructed from documentary sources

“…The reconstruction incorporated all published annually-resolved climate records from southern Africa and surrounding oceans that spanned all or part of the 19th and 20th centuries. These included four documentary series (from Vogel, 1989;Endfield, 2002, 2008; and this study), three coral δ 18 O and/or Sr/Ca series (Zinke et al, 2004;Zinke et al, 2009), one treering width series (Therrell et al, 2006), a baobab tree-ring isotope series (Woodborne et al, 2015) and two rainfall series derived from ships' logs .…”

“…For the SRZ, these included three documentary-derived series (from Vogel, 1989;, three coral δ18O and/or Sr/Ca series (Zinke et al, 2004;Zinke et al, 2009), and a single tree-ring width series (Therrell et al, 2006). The results of the current study, two rainfall series for Mthatha (Eastern Cape) and Royal National Park (KZN) derived from ships' logs , and a baobab tree-ring isotope series from north-eastern South Africa (Woodborne et al, 2015) were added as part of the current reconstruction.…”

Wicked Social-Ecological Problems Forcing Unprecedented Change on the Latitudinal Margins of Coral Reefs: the Case of Southwest Madagascar

“…Temporal trends in environmental conditions on the GRT, in Toliara, and in the region were assessed over a period of ca. 50 years, based on available historical records, recently collected data, and environmental proxies from coral cores taken in Ranobe lagoon off Ifaty, north of Toliara (Zinke et al 2004(Zinke et al , 2009; Fig. 1, Table 1).…”

“…We evaluated the similarity in responses between villages by cluster analysis (Ward method) and then plotted the village respondents' mean agreement with the six restrictions for the two clusters formed from the similarity analysis. 18 O analysis from three coral cores taken off Ifaty and Toliara show the highest SSTs of the entire record since the early 1970s superimposed over a more gradual SST rise over the 20th century (Zinke et al 2004(Zinke et al , 2009). The coral δ 18 O SST trend between 1950 and 1995 was 0.016°C y -1 (Table 1), in close agreement with the rise reported from gridded SST (McClanahan et al 2009).…”