Coral record of southeast Indian Ocean heat waves with intensified Western Pacific temperature gradient

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1 Coral record of southeast Indian Ocean heat waves with intensified Western Pacific temperature gradient Jens Zinke, A. Hoell, J. Lough, M. Feng, A. Kuret, H. Clarke, K. Rankenburg, M. McCulloch Carlos M. Duarte Director, The UWA Oceans Institute

2 Marine heat wave 2011 a glimpse of the Future for WA reefs? Ningaloo Niño Moore et al., 2012 Sea temperatures were >3 C above normal during Feb/March 11 First ever large-scale coral bleaching and mortality event off W Australia No Southern Refugia! 2

3 La Niña & Leeuwin Current heat up SEIO after Feng, 2008 Feng et al., 2013 Sci. Reports Leeuwin Current is main oceanographic feature that connects with the warm water flow through Indonesia and NW Australian shelf 3

4 Coral paleoclimatology Large, Indo-Pacific massive coral colonies as ocean sensors: Porites sp. Foto: E. Matson Milling powder for chemistry 4

5 Geochemical fingerprinting Coral skeleton geochemical fingerprint of: Sea Surface Temperature (Sr/Ca, 18 O) Continuous records for >200 years with seasonal/yearly resolution Here we use yearly resolution Objectives Provide long-term natural baselines for our coral reefs Record Historical exposure to heat waves Assess the drivers of heat waves 5

6 Ningaloo Niño/Niña s in proxy data Reconstructed SSH from paleo-enso and HAI coral SST Detrended time series shows Strong SST/SSH events , post 1980 Yearly anomalies pick up seasonal extremes! ENSO strength not linearly related to SST/SSH Ningaloo Niño/Niña s Zinke et al. Nature Comms

7 Remote and Local winds drive SST/SSH extremes West Pacific and WA reefs Strongly connected through: Ocean Currents driven by Zonal and Meridional winds Anomalous Cyclonic cell off WA Winds linked to low SLP Length of wind arrows proportional to correlation with H. Abrolhos SST Zinke et al. Nature Comms

8 WP SST gradient and SE Indian Ocean WPG defined by Hoell and Funk 2013 Hoell and Funk 2013 J.of Climate; Hoell et al Climate Dyn.; Hoell et al Climate Zinke et al., in revision 8

9 WPG as a unified index for Pacific modes SST based on ERSST 1948 to 2012 Hoell et al. submitted 9

10 West Australia coral composite SST Indonesian warm pool SST reconstruction D Arrigo et al (IWP06) SEIO proxy SST tracks IWP record, yet SEIO cooler for most of 19 th century Best agrement for detrended anomalies vs mean Strongest multi-decadal variations between Zinke et al., in revision 10

11 Paleo-WPG 1782 to 1992 D Arrigo et al Wilson et al Zinke et al., in revision 11

12 WPG and SEIO SST Interannual and decadal variations in instrumental and paleo-wpg co-vary with SEIO SST Strength of WPG varies during ENSO events La Nina and negative WPG linked to warm SEIO SST anomalies Yet, WPG intensity enhance or weaken SEIO SST anomalies Zinke et al., in revision How does the WPG influence SEIO SST? 12

13 WPG, SST and sea level coastal waveguide Ocean advection strongest source of connectivity though ITF-Holloway- Leeuwin Current Ningaloo Nino events: 2/3 from Leeuwin Current advection, 1/3 from heat flux anomalies (Benthuysen et al. 2014) Mutli-decadal variations in WPG strongly linked to SEIO SST and SSH Zinke et al. in revision 13

14 WPG - SEIO heat flux/energy terms Zinke et al., in revisio 14

15 Conclusions Extreme marine heat waves affecting the SEIO are linked to the behaviour of the Western Pacific SST gradient on decadal to multidecadal timescales Most pronounced when a strong zonal SST gradient between the western and central Pacific co-occurs with strong La Niña s WPG is potentially a unified index for Pacific SST modes WPG during ENSO drives the SEIO sea level and SST response via W Pacific wind forcing Ocean advection of warm anomalies from ITF and Meridional winds off WA important for SST amplification during Ningaloo Niño/Niña s WPG forces large changes in heat flux and energy terms that exacerbate SEIO heatwaves by moistening the lower atmosphere 15

16 Pacific SST modes Largest negative WPG in 1999! Hoell et al. submitted 16

17 Pacific SST modes influence WPG Multiple modes of Pacific SST variability can act with considerable strength simultaneously ENSO and PDV strongly contributed to SST over the Nino4 region PMULTI explains the warming trend of west Pacific SST between 1948 and 1990 and step-wise jump in the mid- 1990s. Hoell et al. submitted 17