Split northern westerlies during the Little Ice Age

Abstract The Little Ice Age (LIA) was the coldest period of the past millennium, characterized by high-density volcanism, low solar activity, and increased Northern Hemisphere sea-ice cover. Past studies of LIA circulation changes over the North Atlantic sector have typically referenced the North Atlantic Oscillation (NAO), though recent studies have noted that LIA climate patterns appear to be possess complexity not captured by an NAO analog. Here, we present a new precipitation-sensitive stalagmite record from northern Italy that covers the past 800 years at high resolution. Combined with terrestrial and marine records in the North Atlantic realm, we show that in the early LIA (1470-1610 C.E.), a multi-decadal scale atmospheric blocking over northern Europe split the westerlies away from central and northern Europe, and towards the Arctic and the Mediterranean. This enhanced blocking results in a cold and dry climate over central and northern Europe, and wetter conditions over the Mediterranean. The LIA atmospheric blocking could be caused by the concurrent sea-ice reduction in the Arctic and the Spörer solar minimum. With ongoing ice melting in the northern high latitudes and decreasing solar irradiance in the coming years, the early LIA may potentially serve as an analog for European hydroclimatic conditions in the coming decades.