Fennoscandian freshwater control on Greenland hydroclimate shifts at the onset of the Younger Dryas

Abstract

Sources and timing of freshwater forcing relative to hydroclimate shifts recorded in Greenland ice cores at the onset of Younger Dryas, ∼12,800 years ago, remain speculative. Here we show that progressive Fennoscandian Ice Sheet (FIS) melting 13,100–12,880 years ago generates a hydroclimate dipole with drier–colder conditions in Northern Europe and wetter–warmer conditions in Greenland. FIS melting culminates 12,880 years ago synchronously with the start of Greenland Stadial 1 and a large-scale hydroclimate transition lasting ∼180 years. Transient climate model simulations forced with FIS freshwater reproduce the initial hydroclimate dipole through sea-ice feedbacks in the Nordic Seas. The transition is attributed to the export of excess sea ice to the subpolar North Atlantic and a subsequent southward shift of the westerly winds. We suggest that North Atlantic hydroclimate sensitivity to FIS freshwater can explain the pace and sign of shifts recorded in Greenland at the climate transition into the Younger Dryas.

Shotgun Environmental DNA, Pollen, and Macrofossil Analysis of Lateglacial Lake Sediments From Southern Sweden

“…The LOI% values of the two cores mirror the changes in sediment organic matter content and are almost identical to those obtained earlier for Hässeldala Port cores (Wohlfarth et al, 2017). The common features of the LOI% curves therefore allow precise statistical alignments to master core #5 (Table S1) for which an excellent chronological framework has been established (Muschitiello et al, 2015;Wohlfarth et al, 2017). Using the statistical alignments described in Muschitiello et al (2015) and Wohlfarth et al (2017), we transferred the chronology of core #5 to cores #7.4 and 8 to obtain an age assignment for each of our samples ( Table 1).…”

“…The samples were dried overnight at 105 • C and subsequently ignited at 550 • C following the procedures described in Heiri et al (2001) (Table S1). To obtain a timescale for the two new cores, we adopted the core-to-core alignment of Muschitiello et al (2015) and described in Wohlfarth et al (2017). This approach is based on a statistical correlation of the LOI% curves of #7.4 and #8 to that of master core #5 (Table S1), which serves as a chronological template for all of Hässeldala's sediment cores (Wohlfarth et al, 2017).…”

Massive remobilization of permafrost carbon during post-glacial warming

“…11,650 yBP) during which the Northern Hemisphere experienced an abrupt temperature increase. The YD cooling event was a sudden return to near-glacial conditions during last deglaciation, likely to be triggered by atmosphere–ocean feedback associated with meltwater fluxes and rapid sea ice expansion combined with a weakened Atlantic Meridional Overturning Circulation141516. Ice cores from Greenland have documented the re-establishment of the post-glacial warming in the δ 18 O record17 as a sudden temperature increase.…”

A chironomid-based mean July temperature inference model from the south-east margin of the Tibetan Plateau, China

“…The application of these transfer functions has provided quantitative temperature data since the last glacial period in many regions of the world (e.g. Woodward and Shulmeister, 2007;Rees and Cwynar, 2010;Samartin et al, 2012;Chang et al, 2015b;Muschitiello et al, 2015;Brooks et al, 2016). Consequently, subfossil chironomids have been the most widely applied proxy for past summer temperature reconstructions.…”