Surface and deep ocean coupling in the subpolar North Atlantic during the last 230 years

The subpolar North Atlantic Ocean (SPNA) is of key importance for modulating the climate of NW Europe because of heat loss to the atmosphere from the North Atlantic Current. Although hydrographic properties of the surface SPNA vary on interannual to multidecadal timescales, hydrographic time series scarcely extend back beyond the 1950s. We present a 230 year long record of SPNA surface conditions reconstructed from a very high accumulation rate core that also registers changes in deep flow speed in the Iceland Basin. A lagged correlation is observed between the records of deep flow speed and stable oxygen isotopic composition of the surface SPNA (δ¹⁸O_w), with strongest correlation when the paleoflow speed record leads by 15\textendash20 years. This offset may to some extent reflect size-selective biological mixing of the sediment. Nonetheless, these records reveal a decadal-scale coupling between surface and deep ocean variability over the past 230 years, possibly driven by the North Atlantic Oscillation, with implications for North Atlantic circulation and climate.