The evolutionary heritage and ecological uniqueness of Scots pine in the Caucasus ecoregion is at risk of climate changes

Scots pine is one of the most widely occurring pines, but future projections suggest a large reduction in its range, mostly at the southern European limits. A significant part of its range is located in the Caucasus, a global hot-spot of diversity. Pine forests are an important reservoir of biodiversity and endemism in this region. We explored demographic and biogeographical processes that shaped the genetic diversity of Scots pine in the Caucasus ecoregion and its probable future distribution under different climate scenarios. We found that the high genetic variability of the Caucasian populations mirrors a complex glacial and postglacial history that had a unique evolutionary trajectory compared to the main range in Europe. Scots pine currently grows under a broad spectrum of climatic conditions in the Caucasus, which implies high adaptive potential in the past. However, the current genetic resources of Scots pine are under high pressure from climate change. From our predictions, over 90% of the current distribution of Scots pine may be lost in this century. By threatening the stability of the forest ecosystems, this would dramatically affect the biodiversity of the Caucasus hot-spot.

Deglacial to postglacial history of Nares Strait, Northwest Greenland: a marine perspective from Kane Basin

A radiocarbon-dated marine sediment core retrieved in Kane Basin, central Nares Strait, was analysed to constrain the timing of the postglacial opening of this Arctic gateway and its Holocene evolution. This study is based on a set of sedimentological and geochemical proxies of changing sedimentary processes and sources that provide new insight into the evolution of ice sheet configuration in Nares Strait. Proglacial marine sedimentation at the core site initiated ca. 9.0 cal ka BP following the retreat of grounded ice. Varying contributions of sand and clasts suggest unstable sea ice conditions and glacial activity, which subsisted until ca. 7.5 cal ka BP under the combined influence of warm atmospheric temperatures and proglacial cooling induced by the nearby Innuitian (IIS) and Greenland (GIS) ice sheets. An interval rich in ice-rafted debris (IRD) is interpreted as the collapse of the ice saddle in Kennedy Channel ca. 8.3 cal ka BP that marks the complete opening of Nares Strait and the initial connection between the Lincoln Sea and northernmost Baffin Bay. Delivery of sediment by icebergs was strengthened between ca. 8.3 and ca. 7.5 cal ka BP following the collapse of the buttress of glacial ice in Kennedy Channel that triggered the acceleration of GIS and IIS fluxes toward Nares Strait. The destabilisation in glacial ice eventually led to the rapid retreat of the GIS in eastern Kane Basin at about 8.1 cal ka BP as evidenced by a noticeable change in sediment geochemistry in our core. The gradual decrease in carbonate inputs to Kane Basin between ∼8.1 and ∼4.1 cal ka BP reflects the late deglaciation of Washington Land. The shoaling of Kane Basin can be observed in our record by the increased winnowing of lighter particles as the glacio-isostatic rebound brought the seabed closer to subsurface currents. Reduced iceberg delivery from 7.5 to 1.9 cal ka BP inferred by our dataset may be linked to the retreat of the bordering ice sheets on land that decreased their number of marine termini.

Deglacial to postglacial history of Nares Strait, Northwest Greenland: a marine perspective

A radiocarbon dated marine sediment core retrieved in Kane Basin, central Nares Strait, was analysed to constrain the timing of the postglacial opening of this Arctic gateway and its Holocene evolution. This study is based on a set of sedimentological and geochemical proxies of changing sedimentary processes and sources that translate into ice sheet configuration in the strait. Proglacial marine sedimentation at the core site initiated ca. 9.0 cal. ka BP following the retreat of grounded ice. Unstable sea surface conditions subsisted until 7.5 cal. ka BP under the combined influence of warm atmospheric temperatures and proglacial cooling induced by the nearby Innuitian (IIS) and Greenland (GIS) ice sheets. The collapse of the ice saddle in Kennedy Channel at 8.3 cal. ka BP marks the complete opening of Nares Strait and the initial connection between the Lincoln Sea and northernmost Baffin Bay. Delivery of sediment by icebergs was strengthened between 8.3 and 7.5 cal. ka BP following the collapse of the buttress of glacial ice in Kennedy Channel that triggered the acceleration of GIS and IIS fluxes toward Nares Strait. The destabilisation in glacial ice eventually led to the rapid retreat of the GIS in eastern Kane Basin at 8.1 cal. ka BP as evidenced by a noticeable change in sediment source in our core. The gradual decrease of carbonate inputs to Kane Basin between 8.1 and 4.1 cal. ka BP reflects the late deglaciation of Washington Land. The shoaling of Kane Basin can be observed in our record by the increased winnowing of lighter particles as the glacio-isostatic rebound brought the seabed closer to subsurface currents. Our dataset suggests reduced iceberg delivery from 7.5 to 1.9 cal. ka BP in relation to the Neoglacial cooling that likely enhanced sea ice occurrence, thus suppressing calving and/or the drifting of icebergs in Nares Strait.