The Times Australia
The Times World News

.

Record low Antarctic sea ice is another alarming sign the ocean's role as climate regulator is changing

  • Written by Craig Stevens, Professor in Ocean Physics, National Institute of Water and Atmospheric Research
Record low Antarctic sea ice is another alarming sign the ocean's role as climate regulator is changing

A changing climate is upon us, with more frequent land and marine heatwaves, forest fires, atmospheric rivers and floods. For some, it is the backdrop to day-to-day life, but for a growing number of people it is a life-changing reality.

It is now more remarkable when a year is not the hottest since our species began to develop civilisations[1].

Whenever we experience extreme climate events, it can be hard to engage with the concept that they are minor blips in the planetary experiment we are conducting. But the main act is taking place elsewhere in the oceans[2], which soak up more than 90% of the excess heat energy.

We are winding up a clockwork spring without knowing exactly when, how fast and how it will unspool. Ocean heating is not so much a canary in a coal mine but a thrashing shark we’ve inadvertently (at least initially) hauled up into our fishing boat.

A bonfire of records

A drop in the area covered by sea ice, both in the Arctic and more recently also in Antarctica, is one of the latest record-breaking changes. These floating expanses of frozen seawater are central to how our world works. They regulate how much light our planet reflects, help ventilate the oceans, and host important ecosystems in the form of algal meadows on their underside.

But now, due to the warming of the ocean, we have the lowest sea ice area ever recorded[3].

Ocean scientists are not used to thinking of rapid change, but the trajectory of the global average temperature on the surface of the ocean has now entered uncharted territory[4] – and fast[5].

This graphs shows global ocean surface temperatures, with the 2023 track at the top.
This graph shows global ocean surface temperatures, with the 2023 track at the top. climatereanalyzer.org, CC BY-ND[6]

We know about the scale of this thanks to satellite technology that can sense small changes in temperature at the ocean surface.

Read more: How much will our oceans warm and cause sea levels to rise this century? We've just improved our estimate[7]

These surface data are just that: the temperature of the very skin of the ocean. To get a sense of warming in the deeper ocean, we use ship-based measurements and a fleet of underwater robots known as Argo[8].

A ship deploys instruments to measure temperature just below the ocean surface.
What satellites measure can differ from temperatures just below the surface or in the deeper ocean. Author provided, CC BY-ND[9]

The global ocean heat transport

The deep ocean is clearly changing[10]. This is because polar sea ice acts as a connector between the atmosphere, the surface of the ocean and deeper waters. With less sea ice, there is less cold, salty, oxygenated water sinking to the deep ocean.

These freezing coastal waters of Antarctica are a crucial engine room for global currents that convey energy around the planet – and this ocean transport mechanism is now changing.

Read more: Torrents of Antarctic meltwater are slowing the currents that drive our vital ocean 'overturning' – and threaten its collapse[11]

One of the unknowns of ocean warming is how the oceans will adjust and store all the heat. Heating the ocean surface makes the upper reaches more stable[12]. This in turn changes how the upper ocean absorbs carbon dioxide.

The difficulty for researchers determining how best to respond is that the processes that move and mix this heat operate over very small scales. It is beyond even our most powerful climate simulators to model exactly how the heat is spread[13], making predictions less certain.

Even if our models could work at very big and very small scales at the same time, they would have few data for validation. This is because very little of the ocean’s mixing has been observed directly.

While we can predict some of this mixing, the ocean is full of surprises. Recently, the Drake Passage has been shown to be even more of a mixing hotspot[14] than previously thought.

An ocean turbulence sensor being deployed in rough conditions.
An ocean turbulence sensor being deployed in rough conditions. Author provided, CC BY-ND[15]

A warming Pacific

A map showing surface temperatures around Aotearoa for May 1, 2023, with stippled areas marking marine heatwaves.
Surface temperatures around Aotearoa NEW Zealand for May 1, 2023. The stippled areas mark marine heatwave conditions. Ben Noll/NIWA/NOAA

Despite the connected ocean, the individual basins have their own characteristics and contributions to climate. Aotearoa New Zealand sits in the southwest corner of the Pacific Ocean, which covers about a third of the globe’s surface.

The Pacific is so large it has its own internal cycles, such as the El Niño Southern Oscillation (ENSO[16]). We have to disentangle these to understand long-term changes.

While El Niño conditions can bring marine heatwaves to some areas of the Pacific, the oceans around Aotearoa New Zealand, especially to the south, are already experiencing nearly constant marine heatwaves.

Read more: It might be the world's biggest ocean, but the mighty Pacific is in peril[17]

The scale of the oceanic contribution to storing heat means any small change to how this has operated over the past millennia may have very large impacts. It is impossible to overstate the urgency with which we need to reduce greenhouse gas emissions.

Technologies that can capture already emitted carbon dioxide have many proponents, but they must not come at the expense of efforts to turn off emission sources. Without removing the drivers of emissions, these stop-gap measures will only delay the inevitable. As the Intergovernmental Panel on Climate Change put it in its latest report[18]:

There is a rapidly closing window of opportunity to secure a liveable and sustainable future for all.

References

  1. ^ develop civilisations (doi.org)
  2. ^ in the oceans (doi.org)
  3. ^ lowest sea ice area ever recorded (www.theguardian.com)
  4. ^ uncharted territory (climatereanalyzer.org)
  5. ^ fast (www.theguardian.com)
  6. ^ CC BY-ND (creativecommons.org)
  7. ^ How much will our oceans warm and cause sea levels to rise this century? We've just improved our estimate (theconversation.com)
  8. ^ Argo (argo.ucsd.edu)
  9. ^ CC BY-ND (creativecommons.org)
  10. ^ deep ocean is clearly changing (doi.org)
  11. ^ Torrents of Antarctic meltwater are slowing the currents that drive our vital ocean 'overturning' – and threaten its collapse (theconversation.com)
  12. ^ more stable (theconversation.com)
  13. ^ spread (doi.org)
  14. ^ mixing hotspot (theconversation.com)
  15. ^ CC BY-ND (creativecommons.org)
  16. ^ ENSO (www.weather.gov)
  17. ^ It might be the world's biggest ocean, but the mighty Pacific is in peril (theconversation.com)
  18. ^ latest report (www.ipcc.ch)

Read more https://theconversation.com/record-low-antarctic-sea-ice-is-another-alarming-sign-the-oceans-role-as-climate-regulator-is-changing-204680

Times Magazine

Building an AI-First Culture in Your Company

AI isn't just something to think about anymore - it's becoming part of how we live and work, whether we like it or not. At the office, it definitely helps us move faster. But here's the thing: just using tools like ChatGPT or plugging AI into your wo...

Data Management Isn't Just About Tech—Here’s Why It’s a Human Problem Too

Photo by Kevin Kuby Manuel O. Diaz Jr.We live in a world drowning in data. Every click, swipe, medical scan, and financial transaction generates information, so much that managing it all has become one of the biggest challenges of our digital age. Bu...

Headless CMS in Digital Twins and 3D Product Experiences

Image by freepik As the metaverse becomes more advanced and accessible, it's clear that multiple sectors will use digital twins and 3D product experiences to visualize, connect, and streamline efforts better. A digital twin is a virtual replica of ...

The Decline of Hyper-Casual: How Mid-Core Mobile Games Took Over in 2025

In recent years, the mobile gaming landscape has undergone a significant transformation, with mid-core mobile games emerging as the dominant force in app stores by 2025. This shift is underpinned by changing user habits and evolving monetization tr...

Understanding ITIL 4 and PRINCE2 Project Management Synergy

Key Highlights ITIL 4 focuses on IT service management, emphasising continual improvement and value creation through modern digital transformation approaches. PRINCE2 project management supports systematic planning and execution of projects wit...

What AI Adoption Means for the Future of Workplace Risk Management

Image by freepik As industrial operations become more complex and fast-paced, the risks faced by workers and employers alike continue to grow. Traditional safety models—reliant on manual oversight, reactive investigations, and standardised checklist...

The Times Features

Is our mental health determined by where we live – or is it the other way round? New research sheds more light

Ever felt like where you live is having an impact on your mental health? Turns out, you’re not imagining things. Our new analysis[1] of eight years of data from the New Zeal...

Going Off the Beaten Path? Here's How to Power Up Without the Grid

There’s something incredibly freeing about heading off the beaten path. No traffic, no crowded campsites, no glowing screens in every direction — just you, the landscape, and the...

West HQ is bringing in a season of culinary celebration this July

Western Sydney’s leading entertainment and lifestyle precinct is bringing the fire this July and not just in the kitchen. From $29 lobster feasts and award-winning Asian banque...

What Endo Took and What It Gave Me

From pain to purpose: how one woman turned endometriosis into a movement After years of misdiagnosis, hormone chaos, and major surgery, Jo Barry was done being dismissed. What beg...

Why Parents Must Break the Silence on Money and Start Teaching Financial Skills at Home

Australia’s financial literacy rates are in decline, and our kids are paying the price. Certified Money Coach and Financial Educator Sandra McGuire, who has over 20 years’ exp...

Australia’s Grill’d Transforms Operations with Qlik

Boosting Burgers and Business Clean, connected data powers real-time insights, smarter staffing, and standout customer experiences Sydney, Australia, 14 July 2025 – Qlik®, a g...