Projection and uncertainty of the poleward range expansion of coral habitats in response to sea surface temperature warming: A multiple climate model study

An improved estimation of the poleward expansion of coral habitats based on the inter-annual variation of sea surface temperatures

“…Many studies have projected the future impacts of rising seawater temperatures on coral habitats using high-and/or low-temperature stress indices (Donner et al 2007;Donner 2009;Teneva et al 2012;van Hooidonk et al 2013;Yara et al 2009Yara et al , 2011Yara et al , 2012Yara et al , 2014. Most studies have used a high-temperature stress index such as degree heating months, which is calculated from positive anomalies relative to mean water temperatures in the warmest months, to project the area and frequency of coral bleaching in several regions (Donner et al 2007;Donner 2009;Teneva et al 2012;van Hooidonk et al 2013;Yara et al 2009Yara et al , 2014.…”

“…Most studies have used a high-temperature stress index such as degree heating months, which is calculated from positive anomalies relative to mean water temperatures in the warmest months, to project the area and frequency of coral bleaching in several regions (Donner et al 2007;Donner 2009;Teneva et al 2012;van Hooidonk et al 2013;Yara et al 2009Yara et al , 2014. Alternatively, some studies (including this one) have used low-temperature indices, which are defined from absolute water temperature values in the coldest months, based on the current distributional limits of coral reefs and corals, and have projected a poleward expansion of coral habitats (Yara et al 2009(Yara et al , 2011(Yara et al , 2012. Yara et al (2011) investigated the potential future poleward expansion of three coral communities in response to rising sea surface temperatures (SSTs) along the coasts of Japan, based on decadal-mean SSTs in the coldest months obtained from multiple climate models and simplified indices of poleward expansion.…”

“…Alternatively, some studies (including this one) have used low-temperature indices, which are defined from absolute water temperature values in the coldest months, based on the current distributional limits of coral reefs and corals, and have projected a poleward expansion of coral habitats (Yara et al 2009(Yara et al , 2011(Yara et al , 2012. Yara et al (2011) investigated the potential future poleward expansion of three coral communities in response to rising sea surface temperatures (SSTs) along the coasts of Japan, based on decadal-mean SSTs in the coldest months obtained from multiple climate models and simplified indices of poleward expansion. However, the estimated decadal-mean speeds of coral expansion were one order smaller than those reported by Yamano et al (2011).…”

“…As discussed in Yara et al (2011), the discrepancy in the rate of coral expansion between the two studies was presumably caused by differences in the coral taxa selected for study. However, the poleward expansion of coral habitats could be affected by inter-annual variation of SST in the coldest months, which was not considered in Yara et al (2011), who rather considered the decadal-mean variation of SST. This concept is described in Fig.…”

“…1 Location of the study sites around Japan where on-site monitoring of the poleward expansion of coral habitats was conducted (eight sites, dots) or has subsequently been examined (two sites, stars). Gray arrows indicate the paths of the Kuroshio and Tsushima Currents selected in Yamano et al (2011) that were representative of subtropical and warm temperate regions, rather than the coral communities described in Yara et al (2011). Furthermore, we compared the simulated patterns of poleward expansion by considering coral mortality based on the inter-annual variation of SST and decadal-mean SST in the coldest months, using the most recent climate model outputs.…”