Drivers of δ 18 O Variability Preserved in Ice Cores From Earth's Highest Tropical Mountain

• Published in: Journal of geophysical research. Atmospheres Vol. 128; no. 19
• Main Authors: Weber, A. M., Thompson, L. G., Davis, M., Mosley‐Thompson, E., Beaudon, E., Kenny, D., Lin, P.‐N., Sierra‐Hernández, R.
• Format: Journal Article
• Language: English
• Published: 16-10-2023
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2023JD039006

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 (δ
18
O) record largely reflects tropical Pacific climate variability, particularly in the NINO3.4 region. By extension, the δ
18
O 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/δ
18
O 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.
The oxygen stable isotope records (δ
18
O) of the new Huascarán ice cores (collected in 2019 from Peru) are a natural archive of tropical Pacific climate and hydrological conditions over the Amazon Basin. This is evidenced by strong correlations between δ
18
O and spatiotemporal sea surface temperature (SST) and precipitation data sets that cover the most recent 60 years of the ice core records. Additionally, the Huascarán δ
18
O records are significantly related to temperatures in the upper atmosphere, suggesting that temperature may also play a critical role in modifying the isotope values. The statistical significance of each of these relationships has also been increasing over the last 60 years, and the rates of increase are greatest between the δ
18
O records from the higher elevation ice core site and the temperature‐related climate data sets. This suggests that the isotope records from the Huascarán Summit (6,768 masl) are more sensitive to large‐scale changes in temperature than the isotope records on the Huascarán Col (6,050 masl). This is the first study to examine ice core records from the Summit of Earth's highest tropical mountain and offers valuable insights into the behavior of δ
18
O in the tropical Andes.
Oxygen stable isotope (δ
18
O) records from the new Huascarán ice cores strongly reflect Pacific climate variability of the most recent 60‐year
Tropical Pacific influences on the Huascarán δ
18
O records have strengthened significantly in the last six decades
δ
18
O from the higher elevation Summit appears to be more sensitive to large‐scale climate change than δ
18
O from the lower‐elevation Col