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<\/p>\nComment: Residents of Te Whanganui-a-Tara Wellington know it is always wise to prepare for any weather \u2013 to pack sunglasses, a raincoat, and at least one extra layer. This \u201cbe prepared for anything\u201d approach can equally be applied to Aotearoa\u2019s ocean weather during this year\u2019s \u201csuper\u201d El Ni\u00f1o. Forecasts are fickle, unexpected outcomes are likely, and preparation is needed.<\/p>\n
El Ni\u00f1o \u2013 as well as its opposite phase, La Ni\u00f1a \u2013 are natural climatic features caused by swings in atmospheric pressure over the Pacific.<\/p>\n
Typically, trade winds over the central Pacific blow from the east, drawing cold, nutrient-rich water from the deep ocean to the surface off the western coast of South America in a process called upwelling.<\/p>\n
But during an El Ni\u00f1o phase, a reversal in atmospheric pressure over the Pacific causes trade winds to weaken and\/or reverse entirely.<\/p>\n
Without easterly winds, upwelling does not occur. Instead, warm, tropical surface waters accumulate in the eastern Pacific, which release heat into the atmosphere, increasing air temperatures.<\/p>\n
El Ni\u00f1o phases vary in strength, but the El Ni\u00f1o currently building in the Pacific is on track to be the strongest recorded. Ocean temperatures in the central Pacific are forecast to reach new heights this summer \u2013 potentially 3.6C hotter than normal. Air temperatures in the coming year will likely reflect these extremes.<\/p>\n
Temperature hikes may be particularly dramatic because this El Ni\u00f1o is occurring against a backdrop of warmer-than-normal air and ocean temperatures caused by climate change. To understand the range of possible effects on Aotearoa\u2019s coast and marine life, we can look at similar past events.<\/p>\n
The last strong El Ni\u00f1o was about a decade ago in 2015\/16, with prior strong events in 1982\/83 and 1998\/99. Taken together, these events provide a good picture of what will happen on land \u2013 stronger, more consistent westerlies throughout the summer, heavier rain along the west coast, and heightened drought and wildfire along the east coast.<\/p>\n
In the ocean, however, the picture is less clear, and ecological effects will likely be mixed.<\/p>\n
<\/p>\n
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Unlike El Ni\u00f1o effects in the eastern Pacific, these phases typically bring slightly cooler-than-average sea surface temperatures to Aotearoa. This dip in ocean temperatures could provide short-term relief for heat-stressed marine ecosystems coping with rapidly warming ocean temperatures because of climate change.<\/p>\n
Persistent westerlies may also increase coastal upwelling along our west coast, fuelling the productivity of photosynthesising organisms such as phytoplankton and kelps, thereby benefiting the species that depend on them for food or habitat.<\/p>\n
Meanwhile, increased rain along the west coast may cause higher freshwater flows into marine environments, increasing coastal sedimentation within heavily logged or farmed watersheds. More sediments in the water have a range of negative effects: they decrease oxygen and light availability for marine organisms, smother bottom-dwelling invertebrates, and reduce the ability of certain organisms (for example cockles, mussels, and sponges) to filter food from seawater.<\/p>\n
While El Ni\u00f1o typically brings cooler water temperatures, we can\u2019t rule out the co-occurrence of marine heatwaves. These heatwaves are becoming longer, more intense, and more frequent with climate change.<\/p>\n
For instance, during the 2015\/16 El Ni\u00f1o, the Tasman Sea off the west coast of Aotearoa experienced a 251-day heatwave<\/a>, with sea temperatures reaching 2.9C above normal. This heatwave profoundly affected the marine environment, as have subsequent ones.<\/p>\n In the South Island, these events resulted in high mortality of salmon stock and habitat-forming kelps, including the coast-wide extinction of bull kelp<\/a>. Throughout Aotearoa\u2019s coastal waters, bleaching and necrosis<\/a> have been observed among marine sponges in response to heatwaves.<\/p>\n In Australia, warm waters have also been linked to outbreaks of new diseases on oyster farms and die-offs of wild p\u0101ua.<\/p>\n Thus, if a marine heatwave occurs this summer, it may have outsized impacts on our coast compared with those of El Ni\u00f1o. The exact influence of El Ni\u00f1o on ocean currents and residual heating in our region are unknown, as are the potential impacts further north of Aotearoa.<\/p>\n Even once this year\u2019s El Ni\u00f1o ends, its lingering impacts on sea and air temperatures, coupled with ongoing climate change, assure us that our ocean \u2013 in both the short- and long-term \u2013 will continue warming.<\/p>\n Events like this remind us that we should be prepared for the unexpected. They should also remind us that we will need an adaptive management approach, one informed by m\u0101tauranga M\u0101ori and robust data collection and analysis, to support decision making in the face of erratic ocean weather and long-term climate change.<\/p>\n","protected":false},"excerpt":{"rendered":"Comment: Residents of Te Whanganui-a-Tara Wellington know it is always wise to prepare for any weather \u2013 to…\n","protected":false},"author":2,"featured_media":624928,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[22],"tags":[273,111,139,69,147],"class_list":["post-624927","post","type-post","status-publish","format-standard","has-post-thumbnail","category-environment","tag-environment","tag-new-zealand","tag-newzealand","tag-nz","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/624927","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=624927"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/624927\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/624928"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=624927"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=624927"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=624927"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}