Fig. 1. Surface temperature reconstruction, from this inversion of borehole data, and from a suite of
atmospheric reanalyses : NCEP-20CR, NCEP-NCAR, ERA-interim, NASA-MERRA and NCEP-CFSR, as well as the outputs of the regional model MAR forced by either NCEP-NCAR or ERA-Interim, and an interpolation of weather station data. A constant temperature offset was used on each dataset to match the absolute temperature (1982-2011 mean) measured in the NEEM borehole, and is reported on the right panel. The circles depict the raw offset between modelled surface temperature, and borehole temperature, the diamonds show the offset after correcting the surface elevation bias (Alt. Corr), and the squares show the elevation-corrected bias in 2 m (3 m for MAR) temperature.
The bottom bars show the age distributions of our reconstruction at several points in time. Before 1980, the reconstructed temperature is the average of many decades, which makes the curve look flat.
Abstract: The Arctic is among the fastest warming regions on Earth, but it is also one with limited spatial coverage of multi-decadal instrumental surface air temperature measurements. Consequently, atmospheric reanalyses are relatively unconstrained in this region, resulting in a large spread of estimated 30-year recent warming trends, which limits their use to investigate the mechanisms responsible for this trend.
Here, we present a surface temperature reconstruction over 1982-2011 at NEEM (51∘ W, 77∘ N), in North Greenland, based on the inversion of borehole temperature and inert gas isotope data. We find that NEEM has warmed by 2.7±0.33∘C over the past 30 years, from the long-term 1900-1970 average of -28.55±0.29∘C. The warming trend is principally caused by an increase in downward longwave heat flux. Atmospheric reanalyses underestimate this trend by 17%, underlining the need for more in situ observations to validate reanalyses.
Authors : Anais J. Orsi, Kenji Kawamura, Valérie Masson-Delmotte, Xavier Fettweis, Jason E.Box, Dorthe Dahl-Jensen, Gary D. Clow, Amaelle Landais, Jeffrey P. Severinghaus
Reference : Geophysical Research Letters, doi: 10.1002/2016gl072212, 2017
Maj : 16/05/2017 (138)