Halting Irreversible Antarctic Changes Hinges on Today's Decisions, Study Warns

United States - Ekhbary News Agency

Halting Irreversible Antarctic Changes Hinges on Today's Decisions, Study Warns

The trajectory of the Antarctic Peninsula's future, a crucial barometer for climate change on the southernmost continent, is inextricably linked to projected greenhouse gas emissions levels by the year 2100, according to new research. A comprehensive study published in Frontiers in Environmental Science underscores that the choices made today regarding these emissions will determine whether the fragile Antarctic ecosystem faces irreversible transformations.

The Antarctic Peninsula serves as an "alarm bell" for the entire continent. While a relatively small fraction of Antarctica's landmass, its significance is amplified by the presence of fisheries, tourism, and scientific research stations. Dr. Bethan Davies, a glaciologist at Newcastle University in England, emphasizes that changes occurring on the peninsula do not remain isolated. "Changes that happen in the Antarctic Peninsula also don’t stay in the Antarctic Peninsula," she stated.

Davies explains that the retreat of glaciers in the southern part of the peninsula can render glaciers in West Antarctica more susceptible to melting. Furthermore, a reduction in sea ice surrounding the peninsula exacerbates warming in the broader Southern Ocean. This, in turn, can impede the formation of Antarctic Intermediate Water, a vital water mass that connects the Southern Ocean to the global oceanic circulation system. A decrease in sea ice also directly translates to diminished populations of krill (Euphausia superba), the tiny crustaceans forming the base of the Southern Ocean's food web.

Grim Futures, Yet a Window for Action

As of 2019, with global average temperatures approximately 1 degree Celsius above pre-industrial levels, the Antarctic Peninsula was already exhibiting pronounced changes. Relatively warm Circumpolar Deep Water swirling near the peninsula was accelerating ice melt, and several massive ice chunks had calved from mainland glaciers. Despite these shifts, the adjacent marine food web, reliant on sea ice and krill, had largely remained intact.

However, the current situation is more precarious. "Unfortunately, we’re now at about 1.4 degrees C of warming," Davies noted. The aspirational target for the planet has been to limit future warming to no more than 1.5 degrees C above pre-industrial levels. Yet, in November, the UN Environment Programme issued a stark assessment, indicating a "zero percent chance" that the world will meet this goal, as nations continue to fall short of their emissions reduction commitments. This concerning reality motivated the researchers to investigate the peninsula's potential futures under various emission scenarios.

The study outlines three distinct global warming scenarios by 2100, each predicated on different future greenhouse gas emission pathways:

• Best-Case Scenario (1.8°C warming): Under this scenario, with global temperatures rising to 1.8°C above pre-industrial levels, the marine food web would contract due to shrinking winter sea ice and warming ocean temperatures. Wildlife populations would begin to shift, with species less dependent on krill and sea ice, such as fur seals, elephant seals, and gentoo penguins (Pygoscelis papua), becoming more prevalent.
• Medium-High Emissions Scenario (3.6°C warming): With medium-to-high greenhouse gas emissions leading to approximately 3.6°C of warming by 2100, sea ice concentration would dramatically decrease. Warmer Circumpolar Deep Water would increasingly intrude, eroding the peninsula's ice shelves. Extreme weather events, including marine heatwaves and atmospheric rivers, would escalate in both severity and frequency.
• Worst-Case Scenario (4.4°C warming): This scenario, driven by very high greenhouse gas emissions, projects global warming of about 4.4°C relative to pre-industrial times by 2100. It magnifies the impacts seen in the medium-high scenario. Sea ice coverage could diminish by 20%, posing a severe threat to krill-dependent species like whales and penguins, and contributing to global ocean warming. The Larsen C ice shelf, which famously lost a Delaware-sized iceberg in 2017, would likely collapse entirely by 2100. The George VI ice shelf, currently buttressing inland ice, might collapse by 2300, potentially raising global sea levels by as much as 116 millimeters.

The Specter of Irreversible Change

What heightens the concern is that many of these projected changes would be irreversible on human timescales. "Once you start to retreat glaciers, you trigger marine ice sheet instability, and that process is essentially irreversible. It’s very difficult to regrow those glaciers," Davies explained. Similarly, sea ice is exceptionally difficult to recover once lost. Darker open ocean waters absorb more solar heat, making it challenging to cool the waters sufficiently for sea ice to reform.

Peter Neff, a glaciologist at the University of Minnesota who was not involved in the study, stressed the implications: "All of this illustrates what decision makers worldwide should know: Every decision we make to reduce carbon emissions today makes the challenges of the future more manageable."

Neff further commented on the peninsula's role as an indicator: "The Antarctic Peninsula has long been considered the canary in the coal mine for Antarctic Ice Sheet loss… where we’ve seen smaller versions of the ice shelf collapse that scientists fear for West Antarctica." He noted that discussions about Antarctic change often focus on West Antarctica, including the rapidly melting Thwaites Glacier, and proposed geoengineering solutions. "None of those proposed ‘solutions‘ would do anything to save the Antarctic Peninsula," he concluded.

Ekhbary News Agency