There is growing scientific and public interest in the AMOC, a three-dimensional system of ocean currents that act as a “conveyer belt” to distribute heat, salt, nutrients, and carbon dioxide across the world’s oceans. Changes in the AMOC’s strength could impact global and regional climate, weather, sea level, precipitation patterns, and marine ecosystems.

In this research, measurements of the Florida Current were corrected for the secular change in the geomagnetic field to find that the Florida Current, one of the fastest currents in the ocean and an important part of the AMOC, has remained remarkably stable over the past 40 years.

The study published in the journal Nature Communications, the scientists reassessed the 40-year record of the Florida Current volume transport measured on a decommissioned submarine telecommunications cable in the Florida Straits, which spans the seafloor between Florida and the Bahamas. Due to the Earth’s magnetic field, as salt ions in the seawater are transported by the Florida Current over the cable, a measurable voltage is induced in the cable. The cable measurements were analyzed together with measurements from regular hydrographic surveys that directly measure the Florida Current volume transport and water mass properties. In addition, the transport was inferred from cross-stream sea level differences measured by altimetry satellites.

“This study does not refute the potential slowdown of AMOC, it shows that the Florida Current, one of the key components of the AMOC in the subtropical North Atlantic, has remained steady over the more than 40 years of observations,” said Denis Volkov, lead author of the study and a scientist at CIMAS which is based at the Rosenstiel School. “With the corrected and updated Florida Current transport time series, the negative tendency in the AMOC transport is indeed reduced, but it is not gone completely. The existing observational record is just starting to resolve interdecadal variability, and we need many more years of sustained monitoring to confirm if a long-term AMOC decline is happening.”

Understanding the state of the Florida Current is very important for developing coastal sea level forecast systems, assessing local weather and ecosystem and societal impacts.

Since 1982, NOAA’s Western Boundary Time Series (WBTS) project and its predecessors have monitored the transport of the Florida Current between Florida and the Bahamas at 27°N using a 120-km long submarine cable paired with regular hydrographic cruises in the Florida Straits. This nearly continuous monitoring has provided the longest observational record of a boundary current in existence. Beginning in 2004, NOAA’s WBTS project partnered with the United Kingdom’s Rapid Climate Change program (RAPID) and the University of Miami’s Meridional Overturning Circulation and Heatflux Array (MOCHA) programs to establish the first trans basin AMOC observing array at about 26.5N.

The study was supported by NOAA ‘s Global Ocean Monitoring and Observing program (grant #100007298), NOAA’s Climate Variability and Predictability program (grant #NA20OAR4310407), Natural Environment Research Council (grants #NE/Y003551/1 and NE/Y005589/1) and the National Science Foundation (grants #OCE-1332978 and #OCE-1926008).

The report, published in The Lancet Planetary Health, outlines how cities and businesses have the power to play a crucial role and become the “stewards” of critical Earth systems by demonstrating how they can reduce their environmental impact on the planet. The report summarises key findings of phase one of Earth Commission, founded in 2019 with a team of 18 globally esteemed interdisciplinary scholars as commissioners, involving more than 40 researchers in various working groups.

The report builds on the Safe and Just Earth System Boundaries report published in Nature last year, which found that most of the vital limits within which people and the planet can thrive have been surpassed.

One of three lead authors, Distinguished Professor Xuemei Bai, from ANU, who led the working group on Translation, said that companies and cities have the means to act and drastically transform and reduce pressure on the planet.

“Companies and cities have a huge potential to make a difference, especially if they work towards the same goal, which is to ensure the planet can provide for everyone long-term,” she said.

“They are more nimble and flexible than states, and can reduce their pressure on the planet by setting science-based targets in line with our findings.”

Professor Stuart Bunn, from Griffith University, co-led one of the working groups, which focused on the boundaries of freshwater and nutrient pollution.

The report found the planet’s ability to provide and protect is being stretched past its limits, although it remains possible for humans to escape poverty and harm caused by Earth’s system change, if urgent action is taken.

It found the only way to provide for everyone and ensure societies, businesses and economies thrive without destabilising the planet is to reduce inequalities in how critical Earth system resources, such as freshwater and nutrients, are accessed and used, and how responsibilities, such as reducing carbon emission, are shared, alongside economic and technological transformation.

By 2050, unless urgent transformations are made, the researchers argue that Earth’s climate will deteriorate to the point where there will be no “safe and just space” left.

That means that even if everyone on the planet only had access to the resources necessary for a basic standard of living in 2050, the Earth would still be outside the climate boundary.

The researchers say earth systems face the risk of crossing dangerous tipping points, which would cause further significant harm to people around the world unless energy, food and urban systems are urgently transformed.

The paper outlines a series of recommendations to ensure Earth’s climate remains within this so-called “safe and just space.”

• Firstly, a well-coordinated, intentional effort between policymakers, businesses, civil society and communities can push for changes in how we run the economy and find new policies and funding mechanisms that can address inequality whilst reducing pressure on nature and climate.

• Secondly, fundamental to the transformation is more efficient and effective management, sharing and usage of resources at every level of society including addressing the excessconsumption of some communities, which limits access to basic resources for those whoneed them the most.

• Thirdly, investment in sustainable and affordable technologies is essential to help us use fewer resources and to reopen the safe and just space for all, particularly where there is little or no space left.

The report has been published in The Lancet Planetary Health. It is co-authored by more than 60 leading natural and social scientists from across the globe.