Land–sea thermal decoupling and iceberg discharges in the western North Atlantic during Heinrich Stadials 5–3

Abrupt climate changes of the last glacial period, including Dansgaard–Oeschger cycles and Heinrich Stadials (HSs), were contemporaneous with profound disruptions of the Atlantic Meridional Overturning Circulation (AMOC). However, their impacts on the western North Atlantic and adjacent North American continent remain poorly resolved. Here we present a high-resolution multiproxy reconstruction from core MD99-2203 (Cape Hatteras, 35° N), integrating mineralogical and reworked dinocyst data, pollen and foraminiferal assemblages, and iLOVECLIM model simulations to identify HSs and investigate vegetation–ocean linkages during HSs 5–3. In contrast to the western European margin, each HS is marked by continental cold conditions coeval with warm sea surface temperatures (SST) and the onset of iceberg-rafted debris (IRD) deposition near Cape Hatteras, yet the regional landscape remained dominated by open forests. A close up of HS 4 reveals a distinct two-phase structure: an early stage of synchronous cooling in land and SST, associated with peak IRD deposition in the Ruddiman Belt, followed by a post-surge phase when ice-rafted debris reached 31–35° N. During this phase, cold and dry continental conditions contrasted with anomalously warm sea surface temperatures, generating enhanced land–sea thermal gradients. This contrast increased humidity and, together with rising atmospheric CO2 concentration, may have triggered transient forest recovery, which coincided with subsequent surface cooling. Comparisons with transient iLOVECLIM simulations successfully capture the early phase and reveal insightful spatially heterogeneous feedbacks in the later period. Our results reveal complex, evolving land–ocean interactions during abrupt climate events, providing new insights into regional climate dynamics and impacts of AMOC weakening.