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A weather station on a remote island near Antarctica has logged rainfall daily for 75 years. <\/p>\n
When researchers compared that record against ERA5, the reconstruction had missed most of the trend. This was not a rounding error. The difference exceeded a factor of three.<\/p>\n
Island in the storm<\/p>\n
Macquarie Island is a sliver of green halfway between Tasmania and Antarctica, about 21 miles (34 kilometers) long and 3 miles (5 kilometers) wide. King penguins climb its slopes. Elephant seals sprawl on its beaches.<\/p>\n
The island\u2019s weather station has been recording daily rainfall without interruption since 1948 \u2013 one of the only continuous land-based records anywhere in the Southern Ocean.<\/p>\n
Zhaoyang Kong, an atmospheric scientist at Monash University<\/a> in Melbourne, led a team that pored through 45 years of the station\u2019s measurements. <\/p>\n What they found suggests the stormy ocean encircling Antarctica is changing faster than major climate datasets have indicated.<\/p>\n Five weather types<\/p>\n Kong\u2019s team sorted each day from 1979 through 2023 into one of five weather regimes: zonal flow, warm air advection, low pressure systems, cold air advection, and high pressure.<\/p>\n Plain English for the same list \u2013 steady westerlies, warm fronts pushing south, deep cyclones, cold blasts from Antarctica, calm ridges of high pressure.<\/p>\n These five types cover essentially every kind of day Macquarie sees. Together they let the researchers track something bigger: how the region\u2019s main storm<\/a> belt has been changing year to year.<\/p>\n Rainfall keeps increasing<\/p>\n Annual rainfall on the island has climbed 28% since 1979. That works out to nearly 10 extra inches (25 centimeters) of rain a year, soaking the same patch of moss and grass that has always been there.<\/p>\n A separate question was whether the increase came from more storms hitting the island or from storms dropping more rain when they did. Kong\u2019s team checked both.<\/p>\n The answer is mostly the second. The number of cyclones passing through hasn\u2019t really gone up. One wet regime is largely replacing another. Storms themselves are simply heavier.<\/p>\n Where the models miss<\/p>\n Here is the awkward part. ERA5 registers only an 8% rise in rainfall at Macquarie over the same 45 years.<\/p>\n An observed increase of 28 percent. The modeled increase was 8 percent. A major tool used to gauge what is happening across one of Earth\u2019s biggest climate regulators has been quietly missing a chunk of the picture.<\/p>\n Earlier work<\/a> had hinted Southern Hemisphere storm tracks were intensifying. Until this paper, no one had pinned down how wide that gap really was.<\/p>\n The ocean is sweating<\/p>\n Heavier rain has to come from somewhere. In the atmosphere, water is conserved \u2013 what falls as rain has to rise as evaporation upstream.<\/p>\n Evaporation pulls heat off the ocean surface. Kong\u2019s team describes what is happening as the Southern Ocean \u201csweating\u201d \u2013 losing more heat to the air through the extra moisture that rises and eventually falls again.<\/p>\n Their estimate: the Southern Ocean is now cooling itself through evaporation 10% to 15% more than it did in 1979. <\/p>\n This is occurring in a region that already absorbs more excess heat than any other ocean<\/a> on Earth. That adds up.<\/p>\n Freshwater piling up<\/p>\n Rain dumping into seawater dilutes it. If Macquarie\u2019s trend holds more broadly, the team calculates an extra 2,300 gigatonnes of freshwater poured into the high-latitude Southern Ocean every year compared with 1979.<\/p>\n For context, melting Antarctic ice currently delivers somewhere between 200 and 500 gigatonnes a year. Rain is now adding several times more freshwater than the Antarctic ice melt.<\/p>\n Observed trends<\/a> in surface salinity already line up with that picture. Fresher surface water sits lighter on the saltier water below, which can reduce the mixing that brings nutrients up and moves carbon down.<\/p>\n What this changes<\/p>\n That gap between what the island measured and what ERA5 showed was suspected for years. Now it has been measured \u2013 across 45 years, across all five storm types, in full.<\/p>\n Rainfall over the Southern Ocean storm belt is increasing far faster than the standard model picture suggests. The missing piece is intensity, because storms are becoming wetter rather than more frequent.<\/p>\n Climate models tuned against ERA5 will need a closer look. Estimates of how much freshwater is entering the Southern Ocean \u2013 a figure that drives projections for currents, sea ice, and ocean carbon \u2013 likely need to go up.<\/p>\n The windswept little island that produced the data may end up changing how researchers measure the world\u2019s stormiest sea for decades to come.<\/p>\n The study is published in Weather and Climate Dynamics<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read?\u00a0Subscribe to our newsletter\u00a0<\/a>for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on\u00a0EarthSnap\u00a0<\/a>, a free app brought to you by\u00a0Eric Ralls\u00a0<\/a>and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"Climate scientists studying the Southern Ocean rely on a computer reconstruction called ERA5 \u2013 a dataset built from…\n","protected":false},"author":2,"featured_media":459800,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[61,60,82],"class_list":["post-459799","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-ie","tag-ireland","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/459799","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/comments?post=459799"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/459799\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media\/459800"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media?parent=459799"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/categories?post=459799"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/tags?post=459799"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}