Mid-Late Holocene climate variabilities in the Bransfield Strait, Antarctic Peninsula driven by insolation and ENSO activities

The Antarctic Peninsula (AP) is sensitive to global climate changes. Diatom composition was investigated in a sediment core recovered from the Bransfield Strait, in order to reconstruct the changes in surface water conditions over the past ca. 5.8 kyr (mid-late Holocene) in the AP region. A relatively stable mid-Holocene (5.8-3.8 ka) with persistent presence of sea ice was punctuated by a cooling episode at 4.9-4.2 ka, followed by a cooling trend with stronger sea-ice variability during the late Holocene (since 3.8 ka), which enhanced the surface water stratification in the study area. Frequency analysis reveals centennial- to millennial-scale cyclicities resembling the characteristics of solar irradiance and El Nin tilde o-Southern Oscillation (ENSO). In particular, the increasing ENSO activities during the late Holocene resulted in intensified cold Weddell Sea outflow to the Bransfield Strait that increased sea ice presence and duration. This pattern is in contrast to a northerly warm air intrusion induced glacial meltwater discharge to the western AP region, leading to similar sea ice variability to that in the east AP region.