Climate Variability in the Subarctic Area for the Last Two Millennia: Influence of North Atlantic Sector and Millennial Trend.

Understanding climate variability for the last two millennia is an key issue to propose new constraints on climate modeling. This study is based on the Arctic2k database compiled by the PAGES Arctic2k working group. All records meet several quality criteria concerning location, time period span, resolution and age-dating control. All the proxy used are sensitivity to temperature changes. The database high quality allows to investigate climate variability from millennial trend to high frequencies. There is spatially heterogeneous record distribution throughout the Arctic-subarctic area, most of the archives being located in the North Atlantic sector. We divided the study region into 3 sectors (Siberia, Alaska and North Atlantic areas) and compared them to the global Arctic2k temperature reconstruction using statistics and signal analysis method (wavelet coherence). Wavelet coherence allows investigation of the relationships in time-frequency space between two time series and identification of common variability. The results highlight better significant correlations between North Atlantic and global Arctic signals. The results is confirmed by wavelet coherence, showing common variability at centennial to multi-centennial scales. Millennial trends showed significant cooling trends before 1900 A.D., except for two records. Cooling trends are consistent with reconstructed temperatures for north hemisphere and warming trends seemed to be the results of regional particularity. Studying millennial variability also highlights the inconsistency between some marine proxies which reflect summer temperatures. The characterization of centennial to multidecadal variability will be an important issue to link the high frequency variability of paleoclimate series to low frequency variability recorded by instrumental data.