But scientists say the island is changing.
広い地域は湿潤で湿地が多くなり、その一方でプレウロフィラムやスティルボカルパなどの在来の大ハーブは縮小しつつあります。研究者らは長年、降雨量の増加がこうした変化の背後にあるのではないかと疑っていた。 Now, a new study has been published Weather and climate dynamics A sharp increase in rainfall has been confirmed, and this discovery could have implications far beyond this isolated UNESCO World Heritage Site.
Why the Southern Ocean is important
It absorbs large amounts of heat trapped by greenhouse gases, along with a significant portion of the carbon dioxide produced by human activities. Storm systems that pass through this region also shape weather patterns for Australia, New Zealand, and other parts of the world.
だからこそ、気象局とオーストラリア南極局がマッコーリー島で収集した気象観測が非常に貴重なのです。 The island provides one of the only long-term “true” climate records in the Southern Ocean.
これらの詳細な記録には、75 年以上にわたる毎日の降雨量と気象観測が含まれています。 Scientists regularly use them to check the accuracy of satellite data and computer simulations.
Scientists investigate increased rainfall
Previous research has shown that rainfall on Macquarie Island has increased significantly in recent decades. Ecologists also observed that widespread flooding was damaging native vegetation.
But researchers still didn’t fully understand why rainfall was increasing or how the island’s weather system was changing over time.
To find out, scientists analyzed 45 years of daily precipitation observations (1979-2023) and compared them to a widely used climate reconstruction called the ERA5 reanalysis.
The goal was to determine whether this increase was due to an overall increase in storms or an increase in rainfall from storms.
The storm is getting more and more rainy
In comparison, the ERA5 reanalysis detected only an 8% increase, missing most of the observed changes.
Scientists say the trajectory of storms in the Southern Ocean is gradually moving closer to the South Pole over time, and this major change is currently affecting the island’s weather.
But researchers have discovered something important. The increase in precipitation is not primarily due to more storms on the island. Instead, more rain falls when a storm occurs.
One type of rainfall pattern has largely replaced another.これは、降雨システムの総数が重要な要素ではないことを意味します。嵐そのものは、降雨量の点で単純に激しさを増しています。
Global impact beyond Macquarie Island
Researchers say the finding could have major implications if the same rainfall intensification is occurring across the wider Southern Ocean storm belt, and multiple lines of evidence suggest that is the case.
Researchers estimate that by 2023, increased rainfall will add about 2,300 gigatonnes of freshwater annually across the high-latitude Southern Ocean.これは、南極の融解水からの最近の淡水の寄与よりもはるかに大きく、その差は広がり続けています。
As rainfall increases, the salinity of surface water also changes.塩分は、栄養素と炭素が海洋をどのように移動するかに大きな役割を果たしており、これらの変化は、地球の最も重要な炭素吸収源の 1 つである南極海の生産性と化学的性質に影響を与える可能性があることを意味します。
The Southern Ocean may become even more ‘sweaty’
Just as sweat cools the human body, evaporation removes heat from the ocean.曇りの南極海では、海洋が熱を失う主な原因の 1 つは蒸発です。
The Southern Ocean may now be 10 to 15 percent cooler than it was in 1979, due to the increased evaporation required for increased rainfall, according to the study.
In fact, the Southern Ocean may be sweating more as the climate warms, researchers say.
Climate signals scientists can’t ignore
Macquarie Island is just a small piece of land surrounded by the world’s stormiest ocean.
Researchers say the next step is to determine how widespread these changes are across the Southern Ocean storm belt and understand what they mean for the future of Earth’s climate system.
