How sea ice affects the global ocean climate
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National Observer
15-07-2025
- National Observer
Sea ice can be ‘early warning system' for global heating — but the US is halting data sharing
This story was originally published by The Guardian and appears here as part of the Climate Desk collaboration Scientists analysing the cascading impacts of record low levels of Antarctic sea ice fear a loss of critical US government satellite data will make it harder to track the rapid changes taking place at both poles. Researchers around the globe were told last week the US Department of Defence will stop processing and providing the data, used in studies on the state of Arctic and Antarctic sea ice, at the end of this month. Tracking the state of sea ice is crucial for scientists to understand how global heating is affecting the planet. Sea ice reflects the sun's energy back out to space but, as long-term losses have been recorded, more of the planet's ocean is exposed to the sun's energy, causing more heating. The National Snow and Ice Data Center, based at the University of Colorado, maintains a Sea Ice Index used around the world to track in near real-time the extent of sea ice around the globe. In two updates in the past week, the centre said the US government's Department of Defence, which owns the satellites that contain onboard instruments used to track sea ice, would stop 'processing and delivering' the data on 31 July. The US Department of Defense's decision to halt sharing of critical sea ice data "couldn't come at a worse time," according to researchers. Climate scientists have been warning that Trump administration cuts have targeted climate functions across government, and there has been fears the sea ice data could be targeted. The news comes as new research, some of which relied on the data, found that record low amounts of sea ice around Antarctica in recent years had seen more icebergs splintering off the continent's ice shelves in a process scientists warned could push up global sea levels faster than current modelling has predicted. Dr Alex Fraser, a co-author of the research at the Australian Antarctic Program Partnership (AAPP), said NSIDC's sea ice data was 'our number one heart rate monitor' for the state of the planet's ice. 'It's our early warning system and tells us if the patient is about to flatline. We need this data and now [the scientific community] will be forced to put together a record from a different instrument. We won't have that continued context that we have had previously.' NSIDC has said it is working with alternative and higher-resolution instruments from a different satellite, but has warned that data may not be directly comparable with the current instruments. Fraser said: 'We are seeing records now year on year in Antarctica, so from that perspective this could not have come at a worse time.' Dr Walt Meier, a senior scientist at NSIDC, said there were other 'passive microwave instruments' that could keep the long-term record going, but he said differences with older sensors created a 'a challenge to make the long-term record consistent and there will be some degradation in the consistency of the long-term record.' 'I think we will end up with a robust and quality record that users can have confidence in,' Meier said, but said this would add to uncertainty to estimates of trends. Asked why the government was stopping the data, he said because 'everything is old and resources are limited, my guess is that it is not worth the time and effort to upgrade the systems for such old sensors, which may fail at any time.' The research, published in the journal PNAS Nexus, found a link between increasing numbers of icebergs calving from floating ice shelves and the loss of sea ice. While the loss of sea ice does not directly raise sea levels, the research said it exposed more ice shelves to wave action, causing them to break apart and release icebergs faster. Glaciologist Dr Sue Cook, also from AAPP, said 'like a cork in a bottle' those shelves help to slow down the advance of land-based ice that does raise sea levels if it breaks off into the ocean. She said the higher rates of iceberg calving seen in Antarctica were not accounted for in calculations of how quickly the ice sheet might break apart and contribute global sea levels. 'If we shift to this state where summer sea ice is very low but we continue using models based on previous periods, then we will definitely underestimate how quickly Antarctica will contribute to sea level rise,' she said. The study also outlined other knock-on effects from the record low sea ice levels in the Antarctic, including the loss of more seals and penguins if trends continued. As many as 7,000 emperor penguin chicks died in late 2022 after the early break-up of the stable ice they used for shelter while they grow their waterproof plumage. A US Navy spokesperson confirmed the data processing from its defence meteorological satellite program (DMSP) would stop on 31 July 'in accordance with Department of Defense policy.' DMSP is a joint program owned by the US Space Force, the spokesperson said, and was scheduled for discontinuation in September 2026. 'The Navy is discontinuing contributions to DMSP given the program no longer meets our information technology modernization requirements.'
Perth Now
01-07-2025
- Perth Now
Sea ice loss risks more icebergs, threatens wildlife
The oceans around Antarctica have been trending warmer leading to more ice loss. (HANDOUT/AUSTRALIAN ANTARCTIC DIVISION) The oceans around Antarctica have been trending warmer leading to more ice loss. (HANDOUT/AUSTRALIAN ANTARCTIC DIVISION) Credit: AAP Extreme sea ice loss in Antarctica over the past few years is leading to higher ocean temperatures, more icebergs and habitat dangers for penguins. The oceans surrounding the southern continent have already been trending warmer than average and researchers say the ongoing loss of sea ice is contributing as dark water absorbs more sunlight without a reflective frozen barrier. Species like the Crabeater seal and Adelie penguin rely on sea ice for habitat, with the latter reliant on large chunks during their "catastrophic moult" period when they need to stay dry for weeks at a time. Less sea ice will make it harder for the penguins to find a suitable spot to shed their feathers, leaving them more exposed to predators. Tougher conditions for ships supplying Antarctic missions are also a problem with low ice coverage, the international study led by Australian Antarctic Program Partnership researchers has found. Really low summer sea ice is also associated with more icebergs breaking away from the coastline. Years with the least summer sea ice have produced more than twice as many icebergs as the years with the most summer sea ice. Lead author of the study, the AAPP's Edward Doddridge, said up until about 2015, sea ice was around average or even a bit above. "But since 2016 it has been consistently low, and the last few years have been extraordinarily low," he said during a media briefing. The wide-ranging study into the consequences of sea ice loss lands as uncertainty clouds the future of global climate science under the Trump administration. Dr Doddridge said the US Department of Defense planned to stop sharing its global sea ice coverage satellite data with the international community. The uncertainty was "deeply concerning", the sea ice scientist said, but other country's satellites would continue to supply some information. Other Australian-based climate researchers have been alert to risks hanging over earth observation data and climate modelling, given the US has traditionally played a major role. Christian Jakob, director of the Australian Research Council Centre of Excellence for 21st Century Weather, was worried about the growing possibility of losing access to the satellite data that was key to global cloud coverage research. Cloud cover shrinkage is thought to be contributing to unexpectedly fast warming. "If those satellites were not renewed, if there were no successors to these satellite missions, then some of the information we have will disappear," Professor Jakob told AAP. Research into the impacts of sea ice loss highlights a number of knowledge gaps but report co-author Will Hobbs, also from the University of Tasmania's AAPP, said the findings supported a rapid transition to net zero. "Climate projections indicate that continued greenhouse gas emissions will accelerate the changes in Antarctica and the Southern Ocean that we're already seeing, and exacerbate the far-reaching negative impacts of sea-ice loss," Dr Hobbs said.
The Age
01-07-2025
- The Age
How sea ice affects the global ocean climate
This map is a Spilhaus projection, showing the world's seas and oceans as a single body of water, centred on Antarctica and bordered by continents. Source: Australian Antarctic Program Partnership.
