Zealandia rules the wind
The sunken continent of Zealandia could play a key role in the Earth’s climate, researchers say.
Zealandia, which New Zealand is part of, sits at a critical crossroads between ocean currents and climate, according to an international team led by the University of Maine and including GNS Science.
The researchers believe ‘‘Zealandia switch’’ led to the world warming at the end of the last glaciation, with the southern hemisphere westerly wind belt – the strongest wind system on Earth – playing an important role.
‘‘The position of the westerlies in relation to Te Riu-a-Ma¯ui / Zealandia determines the way water moves between the warm Pacific Ocean and the cold Southern Ocean,’’ GNS Science geomorphologist David Barrell said.
‘‘Our modelling shows that changes in the southern westerly winds have farreaching consequences for global climate.’’
During the last glaciation, the westerlies were farther north and weaker, he said. ‘‘This lessened atmospheric convection in the tropical Pacific and reduced the production of moisture and transfer of heat into both hemispheres. It made the globe cooler.
‘‘At the end of the last glaciation, the westerlies shifted south and strengthened. This stirred up the ocean and generated more convection, moisture and warmer temperatures.’’
The Zealandia Switch mechanism related to the general position of the southern hemisphere westerly wind belt, and to the role of Zealandia and Australia in controlling ocean currents, the University of Maine (UMaine) said.
‘‘Zealandia presents a physical impediment to ocean current flow. When the westerly wind belt is farther north, the southward flow of warm ocean water from the tropical Pacific is directed north of the New Zealand landmass (glacial mode),’’ the university said. ‘‘With the wind belt farther south, warm ocean water extends to the south of New Zealand (interglacial mode).’’
Computer modelling showed global climate was affected by the latitude at which the westerlies were circulating. When they shifted south, the westerlies invigorated water circulation in the South Pacific and Southern oceans, and warmed surface ocean waters across much of the globe.
UMaine said the new hypothesis was fundamentally different from the long-held view that subtle changes in the Earth’s orbit influenced how the northern hemisphere continental ice sheets regulated ice age climates.
The new hypothesis was that the orbit changes affected the behaviour of southern hemisphere westerly winds, and it was that behaviour which lay at the heart of global ice age cycles.
A key part of the research was the development of timelines showing the extent of glaciers in New Zealand and South America during and since the last ice age. Those findings included a major recession in glaciers in the Southern Alps about 18,000 years ago due to significant climate warming.
The research team’s findings suggested ‘‘a big, fast and global end to the last ice age in which a southern-sourced warming episode linked the hemispheres’’.
UMaine said the southward shift of southern hemisphere westerlies at the end of the last ice age was accompanied by gradual but sustained release of carbon dioxide from the Southern Ocean. That may have helped lock the climate system into a warm interglacial mode.
The researchers suggested the introduction of fossil CO2 into the atmosphere may be reawakening the same dynamics that ended the last ice age, potentially propelling the climate into a new mode.
GNS Science’s Barrell said if the new hypothesis stood up to scrutiny, it would provide a better understanding of what drove prehistoric climate shifts.
Kiwis who travel to Australia when the quarantine-free trans-Tasman bubble opens will not be covered by travel insurance policies if an outbreak in either country leaves them stranded. Stuff understands Cabinet could decide as soon as Monday to open a quarantine-free bubble with Australia from mid-April. House of Travel chief operating officer Brent Thomas said its insurance provider, Allianz Partners, would provide ‘‘a level of cover’’ if an individual or their travel companion contracted Covid-19 before they travelled overseas. ‘‘What the insurance does not provide cover for is if there is a governmentenforced lockdown, change in alert levels. ’’ Flight Centre’s insurance provider, CoverMore, is also offering travellers to Australia cover for some Covid-19-related scenarios but travellers will be on their own if they get stuck. Stranded travellers would have to fork out for extra accommodation costs and changes to flights themselves.
Researchers believe ‘‘Zealandia switch’’ led to the world warming at the end of the last glaciation.
Radio company MediaWorks has begun a company-wide review, a week after allegations of serious misconduct by an employee at The Rock radio station. Maria Dew QC has been appointed to carry out an independent workplace review, MediaWorks announced yesterday. The investigation was sparked by social media posts this week accusing an unnamed radio employee of sexual harassment. Industry sources have confirmed the allegations. Chief executive Cam Wallace said it would be a thorough review into past and current workplace culture and practices. The terms of reference for the investigation were still being determined, but Wallace said MediaWorks would share the observations and recommendations from the review. Announcing the review, Wallace said the executive team and board were ‘‘committed to ensuring MediaWorks is a safe place to work’’.