Climate information preserved in seasonal water isotope at 1 NEEM : relationships with temperature , circulation and sea 2 ice 3 4

14 Analyzing seasonally resolved δ18O ice core data can aid the interpretation of the climate information in 15 ice cores, providing also insights into factors governing the δ18O signal that cannot be deciphered by 16 investigating the annual δ18O data only. However, the seasonal isotope signal has not yet to be investigated in 17 northern Greenland, e.g. at the NEEM (North Greenland Eemian Ice Drilling) ice core drill site. Here we analyze 18 seasonally resolved δ18O data from four shallow NEEM ice cores covering the last 150 years. Based on 19 correlation analysis with observed temperature, we attribute about 70% and 30 % of annual accumulation to 20 summer and winter respectively. The NEEM summer δ18O signal correlates strongly with summer western 21 Greenland coastal temperature and with the first principal component (PC1) of summer δ18O from multiple 22 seasonally resolved ice cores from central/southern Greenland. However, there are no significant correlations 23 between NEEM winter δ18O data and western Greenland coastal winter temperature, or southern/central 24 Greenland winter δ18O PC1. The stronger correlation with temperature during summer and the dominance of 25 summer precipitation skew the annual δ18O signal in NEEM. The strong footprint of temperature in NEEM 26 summer δ18O record also suggests that the summer δ18O record, rather than the winter δ18O record, is a better 27 temperature proxy at the NEEM site. Despite dominant signal of North Atlantic Oscillation (NAO) and Atlantic 28 Multidecadal Oscillation (AMO) in the central-southern ice cores data, both NAO and AMO exert weak 29 influences on NEEM seasonal δ18O variations. The NEEM seasonal δ18O is found to be highly correlated with 30 Baffin Bay sea ice concentration (SIC) in satellite observation period (1979-2004), suggesting a connection of 31 the sea ice extent with δ18O at NEEM. NEEM winter δ18O significantly correlates with SIC even for the period 32 prior to satellite observation (1901-1978). The NEEM winter δ18O may reflect sea ice variations of Baffin Bay 33 rather than temperature itself. This study shows that seasonally resolved δ18O records, especially for sites with 34 seasonal precipitation bias such as NEEM, provide a better understanding of how changing air temperature and 35 circulation patterns are associated with the variability of the δ18O records. 36 37 Clim. Past Discuss., https://doi.org/10.5194/cp-2018-8 Manuscript under review for journal Clim. Past Discussion started: 6 March 2018 c © Author(s) 2018. CC BY 4.0 License.