Climate information preserved in seasonal water isotope at NEEM: relationships with temperature, circulation and sea ice

• Published in: Climate of the Past
• Main Authors: Zheng, Minjie, Sjolte, Jesper, Adolphi, Florian, Vinther, Bo Møllesøe, Steen-Larsen, Hans Christian, Popp, Trevor James, Muscheler, Raimund
• Format: Text
• Language: English
• Published: 2019
• Subjects: Baffin Bay; Greenland; Baffin; ice core; North Atlantic; North Atlantic oscillation; North Greenland; Sea ice
• Online Access: https://doi.org/10.5194/cp-14-1067-2018; https://cp.copernicus.org/articles/14/1067/2018/

Analyzing seasonally resolved δ 18 O ice core data can aid the interpretation of the climate information in ice cores, also providing insights into factors governing the δ 18 O signal that cannot be deciphered by investigating the annual δ 18 O data only. However, the seasonal isotope signal has not yet been investigated in northern Greenland, e.g., at the NEEM (North Greenland Eemian Ice Drilling) ice core drill site. Here, we analyze seasonally resolved δ 18 O data from four shallow NEEM ice cores covering the last 150 years. Based on correlation analysis with observed temperature, we attribute about 70 and 30 % of annual accumulation to summer and winter, respectively. The NEEM summer δ 18 O signal correlates strongly with summer western Greenland coastal temperature and with the first principal component (PC1) of summer δ 18 O from multiple seasonally resolved ice cores from central/southern Greenland. However, there are no significant correlations between NEEM winter δ 18 O data and western Greenland coastal winter temperature or southern/central Greenland winter δ 18 O PC1. The stronger correlation with temperature during summer and the dominance of summer precipitation skew the annual δ 18 O signal in NEEM. The strong footprint of temperature in NEEM summer δ 18 O record also suggests that the summer δ 18 O record rather than the winter δ 18 O record is a better temperature proxy at the NEEM site. Despite the dominant signal of the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO) in the central–southern ice core data, both NAO and AMO exert weak influences on NEEM seasonal δ 18 O variations. The NEEM seasonal δ 18 O is found to be highly correlated with Baffin Bay sea ice concentration (SIC) in the satellite observation period (1979–2004), suggesting a connection of the sea ice extent with δ 18 O at NEEM. NEEM winter δ 18 O significantly correlates with SIC even for the period prior to satellite observation (1901–1978). The NEEM winter δ 18 O may reflect sea ice variations of Baffin Bay rather than temperature itself. This study shows that seasonally resolved δ 18 O records, especially for sites with a seasonal precipitation bias such as NEEM, provide a better understanding of how changing air temperature and circulation patterns are associated with the variability in the δ 18 O records.