Flooding. Droughts. Landslides. Storm surges. Coastal Inundation

These were some of the impacts of a triple-dip La Niña event, which was declared for the Pacific last year. A triple-dip La Niña means that the system developed three years in a row. The first La Niña event was declared in 2020, and again in 2021 and 2022.

La Niña occurs when there is an increase in the strength and intensity of trade winds, which then enhances the warm pool in the Western Pacific, causing sea surface temperatures in the Central and Easter Pacific to become cooler resulting in above normal rainfall in the West.

During a La Niña event, countries in the Central Pacific region, such as Kiribati, Nauru, Tuvalu, and northern Cook Islands will experience below normal rainfall, while countries in the Southwest Pacific, such as parts of Papua New Guinea and Solomon Islands, New Caledonia, Vanuatu, Fiji, Tonga and Niue will see higher than normal rainfall.

The impacts of last year’s La Niña event in the Pacific was highlighted and discussed during the 12th Pacific Islands Climate Outlook Forum (PICOF-12) held last week. Representatives of Pacific National Meteorological and Hydrological Services (NMHSs) and partner agencies such as the Australia Bureau of Meteorology, the National Oceanic and Atmospheric Administration, the National Institute of Water and Atmospheric Research, Commonwealth Scientific and Industrial Research Organisation, Pacific Community and APEC Climate Centre, came together to review climate and ocean conditions from the past six months, and provide outlook for the next six months.

SPREP Climatologist, Philip Malsale, during his presentation, noted that during PICOF-11 held in 2022, conditions favouring continuation ofLa Niña, with the likelihood of drier than normal conditions from island groups near and west of the Dateline and located close to the equator.

These conditions resulted in a drought in northeast PNG, Nauru, Kiribati, Tuvalu, Tokelau and northern Cook Islands. The below normal level of rainfall caused by La Niña saw the people of Nauru having to ration water and resort to using tanks for their water supply.

The same conditions were also recorded in Tuvalu, where a drought was brought on by La Niña from October to December 2022. The Government declared a State of Emergency on 11 November, with people on the island of Funafuti having to ration water – each family receiving six buckets of desalinated water per day.

“It was also forecast that coral bleaching would be enhanced in the tropical west Pacific, and sea levels would be notably higher than normal for most countries in the region. We saw this in Tuvalu, where there were king tides in February this year, with sea level rise measuring 3.325 metres,” Malsale said.

Wetter than normal conditions were forecast for islands located between Palau and central Marshall Islands in the North Pacific, and from southeast PNG to the French Polynesia islands.

New Caledonia recorded nine episodes of heavy rainfall between November 2022 and April 2023. During this period, New Caledonia also experienced rainfall generated by tropical depressions Hale and Irene in January 2023, tropical cyclone Gabrielle in February 2023, and tropical cyclones Judy and Kevin in March 2023.

The heavy rainfall across the country resulted in frequent closures of many roads due to flooding, as well as the deterioration of roads, landslides, and destruction of many crops.

Flooding, landslides and storm surges were recorded in Fiji, with storm surge recorded in Kadavu due to moderate swells generated by TC Irene and the king tides. Niue experienced power disruptions due to heavy rainfall, and crops were more prone to mould and the spread of fungus that affected their overall growth.

“From extreme rainfall, flooding, and landslides, to tropical cyclones and storm surges, the La Niña impacts were felt by all sectors, including infrastructure, aviation, water, agriculture, and tourism. Sadly, it also resulted in the loss of lives, with five people drowning due to flooding in Tahiti, Fiji, including other related deaths in other countries,” Malsale says.

The current state of the El Niño-Southern Oscillation is now back to Neutral, however, models are showing that there is a likelihood of an El Niño event developing later in mid 2023. People are advised to get more information from their National Meteorology and Hydrological Services to prepare for and attempt to minimise the adverse impacts of the potential upcoming El Niño event.