A recent study indicates that a warming event tens of thousands of years ago resulted in the release of carbon dioxide from the deep Southern Ocean. Scientists suggest these findings may inform understanding of potential future impacts from ongoing warming in the Antarctic.
Research Overview
The study, led by scientists from the Laoshan Laboratory in Qingdao, China, and Germany's GEOMAR Helmholtz Centre for Ocean Research Kiel, analyzed sediment cores from the Southern Ocean. The objective was to investigate the behavior of Antarctic Bottom Water (AABW).
Huang Huang, who led the study, stated in a GEOMAR press release, "We wanted to understand how the influence of Antarctic Bottom Water, the coldest and densest water mass in the global ocean, changed during the last deglaciation, and what role it played in the global carbon cycle."
Published in Nature Geoscience, the findings suggest that AABW expansion contributed to the conclusion of the last Ice Age. According to the release, "As the planet warmed and the ice sheets melted between approximately 18,000 and 10,000 years ago, the volume of Antarctic Bottom Water expanded in two distinct phases."
These phases coincided with documented warming events in Antarctica. As vertical mixing within the Southern Ocean intensified, carbon previously stored in the deep ocean was able to re-enter the atmosphere. The research team observed that the deepest waters remained relatively stagnant until global warming commenced. The expansion caused by planetary warming agitated these waters, leading to the release of stored carbon into the atmosphere, which contributed to temperature increases.
Implications of the Research
The study's insights, which extend tens of thousands of years into the past and thousands of meters into the ocean, could have contemporary relevance. Marcus Gutjahr, a GEOMAR geochemist, noted, "Comparisons with the past are always imperfect, but ultimately it comes down to how much energy is in the system. If we understand how the ocean responded to warming in the past, we can better grasp what is happening today as Antarctic ice shelves continue to melt."
In the last half-century, deep Southern Ocean waters have warmed at a faster rate than most other oceanic regions. If current warming patterns and ice thawing mirror historical occurrences, significant quantities of carbon could again be released into the atmosphere, potentially leading to further temperature increases.
Gutjahr emphasized the importance of understanding current ocean conditions to interpret past signals: "If we can trace how Antarctic Bottom Water has changed over the last few thousand years, we can assess more accurately how rapidly the Antarctic Ice Sheet may continue to lose mass in the future." Other studies indicate a decrease in sea ice levels over the past 50 years.
Potential Actions
Advances in this research field could assist policymakers and international organizations in preparing for the potential impacts of sustained global warming. Data concerning sea level rise, food system disruptions, and disease proliferation can inform the development of adaptation strategies. The findings may also contribute to public understanding regarding strategies to mitigate rising temperatures, such as transitions to alternative home energy systems and transportation options.