Modeling the water isotopes in Greenland precipitation 1959–2001 with the meso-scale model REMO-iso
Résumé
Ice core studies have proved the d 18 O in Greenland precipitation to be correlated to the phase of the North Atlantic Oscillation (NAO). This subject has also been investigated in modeling studies. However, these studies have either had severe biases in the d 18 O levels, or have not been designed to be compared directly with observations. In this study we nudge a meso-scale climate model fitted with stable water isotope diagnostics (REMO-iso) to follow the actual weather patterns for the period 1959-2001. We evaluate this simulation using meteorological observations from stations along the Greenland coast, and d 18 O from several Greenland ice core stacks and Global Network In Precipitation (GNIP) data from Greenland, Iceland and Svalbard. The REMO-iso output explains up to 40% of the interannual d 18 O variability observed in ice cores, which is comparable to the model performance for precipitation. In terms of reproducing the observed variability the global model, ECHAM4-iso performs on the same level as REMO-iso. However, REMO-iso has smaller biases in d 18 O and improved representation of the observed spatial d 18 O-temperature slope compared to ECHAM4-iso. Analysis of the main modes of winter variability of d 18 O shows a coherent signal in Central and Western Greenland similar to results from ice cores. The NAO explains 20% of the leading d 18 O pattern. Based on the model output we suggest that methods to reconstruct the NAO from Greenland ice cores employ both d 18 O and accumulation records.
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