Ice cores from Earth’s highest tropical peak provide insight into climate variability
Newswise — COLUMBUS, Ohio – In the first study to examine ice cores from the summit of the highest tropical mountain in the world, new evidence provides unique insight into the climate record of the Amazon Basin over the last six decades.
Nestled within the central Peruvian Andes lies Nevado Huascarán, a tropical mountain whose glaciers preserve the climate histories of the entire region. Researchers have long been interested in studying this area, because unlike ice cores recovered from the poles, core samples taken from tropical areas of the world can reveal a wealth of information about phenomena like El Niño and seasonal monsoons.
The study, by researchers from The Ohio State University and published in JGR Atmospheres, involves four ice core samples – two from mountain col, which is the lowest point between two ridges, and for the first time, two from the summit, nearly 7,000 meters above sea level.
The researchers compared the oxygen-stable isotope records preserved in glacial ice at these different elevations on the mountain. Scientists who study ice cores use isotopes as a proxy for temperature change over time, but in tropical regions interpreting the isotope records can be a more complex process.
Their findings showed that the isotope records share a statistically significant relationship with sea surface temperatures in the Pacific and with rainfall over tropical South America. The oxygen-stable isotopes from the summit were also found to be more sensitive to large-scale changes in tropical Pacific sea surface temperature than the ones found at the lower levels of the mountain.
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Yet for decades, due to the risk of avalanches and hidden snow-lined crevasses, no research expedition had ever been able to reach the peak of Nevado Huascarán to collect these ancient records. That is, until July of 2019, when Thompson and his team successfully navigated their way to the summit of the mountain’s South Peak. The team recovered two ice cores to bedrock from the col drill site – which is 6,050 meters above sea level – and two cores to bedrock from the summit at 6,768 meters above sea level – recovering 471 meters of glacial ice cores in total.
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https://www.newswise.com/articles/ice-cores-from-earth-s-highest-tropical-peak-provide-insight-into-climate-variabilityAbstract
In 2019, four ice cores were recovered from the world's highest tropical mountain, Nevado Huascarán (Cordillera Blanca, Peru; 9.11°S, 77.61°W). Composite hydroclimate records of the two Col cores (6,050 masl) and the two Summit cores (6,768 masl) are compared to gridded gauge-analysis and reanalysis climate data for the most recent 60-year. Spatiotemporal correlation analyses suggest that the ice core oxygen stable isotope (δ18O) record largely reflects tropical Pacific climate variability, particularly in the NINO3.4 region. By extension, the δ18O record is strongly related to rainfall over the Amazon Basin, as teleconnections between the El Niño Southern Oscillation and hydrological behavior are the main drivers of the fractionation of water isotopes. However, on a local scale, modulation of the stable water isotopes appears to be more closely governed by upper atmospheric temperatures than by rainfall amount. Over the last 60 years, the statistical significance of the climate/δ18O relationship has been increasing contemporaneously with the atmospheric and oceanic warming rates and shifts in the Walker circulation. Isotopic records from the Summit appear to be more sensitive to large-scale temperature changes than the records from the Col. These results may have substantial implications for modeling studies of the behavior of water isotopes at high elevations in the tropical Andes.
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023JD039006