Atmospheric response to mid-Holocene warming in the northeastern Atlantic: Implications for future storminess in the Ireland/UK region

Abstract

There is increasing evidence that accelerated warming at high-latitudes is associated with increased climate variability at mid-latitudes, including the frequency and intensity of storms. However, due to short instrumental records our understanding of how ocean-atmosphere dynamics operate during warmer than present climates remains limited. Here we present a palaeoceanographic investigation of the transition between the middle Holocene intervals of the Northgrippian (8.2–4.2 ka) and the late Holocene interval of the Meghalayan (4.2–0 ka) to test the hypothesis of an eastward shift of the Icelandic Low under warmer than present climate scenarios. Reconstructions of bottom water temperatures (BWT) and stable oxygen isotopes (Mg/Ca, δ18O) using the benthic foraminifera Hyalinea balthica reveal warmer than present BWT of up to 2.6 ± 0.7 °C on the Irish Continental Shelf until circa 4.2 ka. The results suggest that Atlantic waters of subtropical origins were more prevalent in the eastern subpolar gyre (SPG) and on the Irish Continental Shelf. We link this oceanographic signature to an eastward shift of the Icelandic Low. We then place our local temperature record into an extra-regional context, using a combination of modern observations and existing palaeo datasets, which enables us to assess the impact of changing atmospheric modes on ocean-atmosphere climate linkages within the North Atlantic Region. The enhanced influence of warm subtropical Atlantic waters recirculating along the boundaries of the SPG under this scenario, would potentially have enhanced melt rates of marine-terminating glaciers on the east Greenland Shelf during the Northgrippian.