Seasonal climate summary southern hemisphere (autumn 2020): another coral bleaching event for the Great Barrier Reef without an active El Niño
Grant A. Smith
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Abstract
Austral autumn 2020, inclusive of the months March, April and May, followed a period of hot and dry conditions over summer that led to high bushfire risk in Australia due to a strong positive Indian Ocean Dipole. The autumn period was also warmer and drier than average overall with strong differences across the states. Notable exceptions were rainfall across New South Wales, Tasmania and Victoria, and rainfall associated with Tropical Cyclone Esther near the Pilbara and the Northern Territory Top End. Overall, Australia maximum mean temperatures were +0.65°C above average, with Western Australia in the top 10 recorded temperatures at +1.53°C above average. South-east Australian rainfall led to flooding and extinguished the remaining fires of the 2019–2020 bushfire season. The rainfall did not reach coastal regions of south-east Queensland where severe rainfall deficiencies persisted. Autumn 2020 was classified as neutral in terms of the El Niño–Southern Oscillation (ENSO) and marks the second time that the Great Barrier Reef has experienced mass coral bleaching due to elevated ocean temperatures in an ENSO neutral year. Elevated sea surface temperatures in the Coral Sea are largely attributed to a general warming trend in the region. Antarctic sea ice extent went from below average to close to average by the end of May 2020, aided by a positive Southern Annular Mode. At the end of autumn 2020, there were early signs of a La Niña event building, with negative temperature anomalies in the subsurface and cooling of sea surface temperatures along equatorial Pacific.
Keywords: Antarctic sea ice, bushfire, coral bleaching, Great Barrier Reef, rainfall, seasonal climate summary, surface temperature, tropical cyclone.
References
Bureau of Meteorology (2020) Special Climate Statement 73 – extreme heat and fire weather in December 2019 and January 2020. (The Bureau) Available at http://www.bom.gov.au/climate/current/statements/scs73.pdf
Donald A, Meinke H, Power B, Wheeler M, Ribbe J (2004) Forecasting with the Madden–Julian Oscillation and the applications for risk management. In ‘Proceedings of the 4th International Crop Science Congress: New Directions for a Diverse Planet’, 26 September–1 October 2004, Brisbane, Qld, Australia. (University of Southern Queensland) Available at https://research.usq.edu.au/item/9xw3y/forecasting-with-the-madden-julian-oscillation-and-the-applications-for-risk-management
FloodList (2020) Papua New Guinea – thousands affected by floods in Gulf Province. In FloodList, 7 April 2020. Available at https://floodlist.com/asia/papua-new-guinea-floods-gulf-province-april-2020 [Verified 4 October 2023]
Goyal R, Jucker M, Sen Gupta A, Hendon HH, England MH (2021) Zonal wave 3 pattern in the Southern Hemisphere generated by tropical convection. Nature Geoscience 14(10), 732-738.
| Crossref | Google Scholar |
Great Barrier Reef Marine Park Authority (2017) Final report: 2016 coral bleaching event on the Great Barrier Reef. Findings of a rapid ecological impact assessment and summary of environmental monitoring and incident response. June 2017. (GBRMPA: Townsville, Qld, Australia) Available at https://elibrary.gbrmpa.gov.au/jspui/bitstream/11017/3206/1/Final-report-2016-coral-bleaching-GBR.pdf
Hall A, Visbeck M (2002) Synchronous variability in the Southern Hemisphere atmosphere, sea ice, and ocean resulting from the annular mode. Journal of Climate 15(21), 3043-3057.
| Crossref | Google Scholar |
Hendon HH, Zhang C, Glick JD (1999) Interannual variation of the Madden–Julian Oscillation during austral summer. Journal of Climate 12(8 PART 2), 2538-2550.
| Crossref | Google Scholar |
Hendon HH, Thompson DWJ, Wheeler MC (2007) Australian rainfall and surface temperature variations associated with the Southern Hemisphere annular mode. Journal of Climate 20(11), 2452-2467.
| Crossref | Google Scholar |
Huang B, Thorne PW, Banzon VF, Boyer T, Chepurin G, Lawrimore JH, Menne MJ, Smith TM, Vose RS, Zhang HM (2017) Extended reconstructed sea surface temperature, version 5 (ERSSTv5): Upgrades, validations, and intercomparisons. Journal of Climate 30(20), 8179-8205.
| Crossref | Google Scholar |
Hughes TP, Kerry JT (2017) Back-to-back bleaching has now hit two-thirds of the Great Barrier Reef. In The Conversation, 12 April 2017. Available at https://theconversation.com/back-to-back-bleaching-has-now-hit-two-thirds-of-the-great-barrier-reef-76092
Hughes TP, Kerry JT, Álvarez-Noriega M, Álvarez-Romero JG, Anderson KD, Baird AH, Babcock RC, Beger M, Bellwood DR, Berkelmans R, Bridge TC, Butler IR, Byrne M, Cantin NE, Comeau S, Connolly SR, Cumming GS, Dalton SJ, Diaz-Pulido G, Eakin CM, Figueira WF, Gilmour JP, Harrison HB, Heron SF, Hoey AS, Hobbs JA, Hoogenboom MO, Kennedy E V, Kuo CY, Lough JM, Lowe RJ, Liu G, McCulloch MT, Malcolm HA, McWilliam MJ, Pandolfi JM, Pears RJ, Pratchett MS, Schoepf V, Simpson T, Skirving WJ, Sommer B, Torda G, Wachenfeld DR, Willis BL, Wilson SK (2017) Global warming and recurrent mass bleaching of corals. Nature 543(7645), 373-377.
| Crossref | Google Scholar | PubMed |
Hughes TP, Kerry JT, Connolly SR, Baird AH, Eakin CM, Heron SF, Hoey AS, Hoogenboom MO, Jacobson M, Liu G, Pratchett MS, Skirving W, Torda G (2019) Ecological memory modifies the cumulative impact of recurrent climate extremes. Nature Climate Change 9(1), 40-43.
| Crossref | Google Scholar |
Joint Research Centre Global Drought Observatory (2020) GDO analytical report: drought in Mozambique and neighbouring countries July 2020. (European Commision) Available at https://www.gdacs.org/Public/download.aspx?type=DC&id=205
Kanamitsu M, et al. (2002) NCEP-DEO AMIP-II reanalysis (R-2). Bulletin of the American Meteorological Society 83(11), 1631-1643.
| Crossref | Google Scholar |
Kuleshov Y, Qi L, Fawcett R, Jones D (2009) Improving preparedness to natural hazards: Tropical cyclone prediction for the Southern Hemisphere. Advances in Geosciences 12, 127-143.
| Crossref | Google Scholar |
McGree S, Smith G, Chandler E, Herold N, Begg Z, Kuleshov Y, Malsale P, Ritman M (2022) Climate change in the Pacific 2022: historical and recent variability, extremes and change. (Climate and Ocean Support Program in the Pacific, Pacific Community: Suva, Fiji) 10.5281/zenodo.10116941
Madden RA, Julian PR (1971) Detection of a 40–50 day oscillation in the zonal wind in the tropical Pacific. Journal of the Atmospheric Sciences 28(5), 702-708.
| Crossref | Google Scholar |
Madden RA, Julian PR (1972) Description of global-scale circulation cells in the tropics with a 40–50 day period. Journal of the Atmospheric Sciences 29(6), 1109-1123.
| Crossref | Google Scholar |
Madden RA, Julian PR (1994) Observations of the 40–50-day tropical oscillation – a review. Monthly Weather Review 122((5), 814-837.
| Crossref | Google Scholar |
Marshall GJ (2003) Trends in the Southern Annular Mode from observations and reanalyses. Journal of Climate 16(24), 4134-4143.
| Crossref | Google Scholar |
National Centers for Environmental Prediction (2019) El Niño/Southern Oscillation (ENSO) diagnostic discussion. (NOAA National Weather Service: College Park, MD, USA) Available at https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_disc_feb2019/ensodisc.shtml
National Institute of Water and Atmospheric Research (2021) Annual Climate Summary: New Zealand climate summary: 2020. Issued: 12 January 2021. (NIWA) Available at https://niwa.co.nz/sites/default/files/2020_Annual_Climate_Summary_Final.pdf
Nolan MKB, Schmidt-Roach S, Davis AR, Aranda M, Howells EJ (2021) Widespread bleaching in the One Tree Island lagoon (Southern Great Barrier Reef) during record-breaking temperatures in 2020. Environmental Monitoring and Assessment 193(9), 590.
| Crossref | Google Scholar | PubMed |
Pörtner H-O, Roberts DC, Masson-Delmotte V, Zhai P, Tignor M, Poloczanska E, Mintenbeck K, Alegría A, Nicolai M, Okem A, Petzold J, Rama B, Weyer NM (Eds) (2019) The Ocean and Cryosphere in a Changing Climate: a special report of the Intergovernmental Panel on Climate Change. (Intergovernmental Panel on Climate Change) Available at https://www.ipcc.ch/site/assets/uploads/sites/3/2019/12/SROCC_FullReport_FINAL.pdf
Puri K, Dietachmayer G, Steinle P, Dix M, Rikus L, Logan L, Naughton M, Tingwell C, Xiao Y, Barras V, Bermous I, Bowen R, Deschamps L, Franklin C, Fraser J, Glowacki T, Harris B, Lee J, Le T, Roff G, Sulaiman A, Sims H, Sun X, Sun Z, Zhu H, Chattopadhyay M, Engel C (2013) Implementation of the initial ACCESS numerical weather prediction system. Australian Meteorological and Oceanographic Journal 63(2), 265-284.
| Crossref | Google Scholar |
Reynolds RW, Rayner NA, Smith TM, Stokes DC, Wang W (2002) An improved in situ and satellite SST analysis for climate. Journal of Climate 15(13), 1609-1625.
| Crossref | Google Scholar |
Risbey JS, Pook MJ, McIntosh PC, Wheeler MC, Hendon HH (2009) On the remote drivers of rainfall variability in Australia. Monthly Weather Review 137(10), 3233-3253.
| Crossref | Google Scholar |
Saji NH, Goswami BN, Vinayachandran PN, Yamagata T (1999) A dipole mode in the tropical Indian ocean. Nature 401(6751), 360-363.
| Crossref | Google Scholar | PubMed |
Smith GA (2019) Seasonal climate summary for the southern hemisphere (autumn 2017): the Great Barrier Reef experiences coral bleaching during El Niño–Southern Oscillation neutral conditions. Journal of Southern Hemisphere Earth Systems Science 69(1), 310-330.
| Crossref | Google Scholar |
Troup AJ (1965) The Southern Oscillation. Quarterly Journal of the Royal Meteorological Society 91(390), 490-506.
| Crossref | Google Scholar |
Watson CS, White NJ, Church JA, King MA, Burgette RJ, Legresy B (2015) Unabated global mean sea-level rise over the satellite altimeter era. Nature Climate Change 5(6), 565-568.
| Crossref | Google Scholar |
Wheeler MC, Hendon HH (2004) An all-season real-time multivariate MJO index: development of an index for monitoring and prediction. Monthly Weather Review 132(8), 1917-1932.
| Crossref | Google Scholar |
Wheeler M, Kiladis GN (1999) Convectively coupled equatorial waves: analysis of clouds and temperature in the wavenumber–frequency domain. Journal of the Atmospheric Sciences 56(3), 374-399.
| Crossref | Google Scholar |
World Meteorological Organization (2021) State of the Climate 2020. WMO-No: 1264. (WMO: Geneva, Switzerland) Available at https://library.wmo.int/idurl/4/56247
Wolter K, Timlin MS (1993) Monitoring ENSO in COADS with a seasonally adjusted principal component index. In ‘Proceedings of the 17th Climate Diagnostics Workshop’, 18–23 October 1992, Norman, OK, USA. pp. 52–57. (NOAA/NMC/CAC, NSSL, Oklahoma Climate Survey, CIMMS and the School of Meteorology, University of Oklahoma) Available at https://psl.noaa.gov/enso/mei.old/WT1.pdf
Wolter K, Timlin MS (1998) Measuring the strength of ENSO events: how does 1997/98 rank? Weather 53(9), 315-324.
| Google Scholar |
Wright PB (1989) Homogenized long‐period Southern Oscillation indices. International Journal of Climatology 9(1), 33-54.
| Crossref | Google Scholar |
