Abrupt high-latitude climate events and decoupled seasonal trends during the Eemian

Abstract

The Eemian (the Last Interglacial; ca. 129–116 thousand years ago) presents a testbed for assessing environmental responses and climate feedbacks under warmer-than-present boundary conditions. However, climate syntheses for the Eemian remain hampered by lack of data from the high-latitude land areas, masking the climate response and feedbacks in the Arctic. Here we present a high-resolution (sub-centennial) record of Eemian palaeoclimate from northern Finland, with multi-model reconstructions for July and January air temperature. In contrast with the mid-latitudes of Europe, our data show decoupled seasonal trends with falling July and rising January temperatures over the Eemian, due to orbital and oceanic forcings. This leads to an oceanic Late-Eemian climate, consistent with an earlier hypothesis of glacial inception in Europe. The interglacial is further intersected by two strong cooling and drying events. These abrupt events parallel shifts in marine proxy data, linked to disturbances in the North Atlantic oceanic circulation regime.

Hot summers ahead? Multi-decadal spring season warming precedes sudden summer temperature rise in pre-anthropogenic climate change

“…This divergence in seasonal response to climatic triggers constrains modelled asynchronous responses determined for the warming episodes during the last deglaciation (Buizert 2015). Such temporal and spatial response estimates suggest that over Greenland, intensive winter warming exceeds the ultimate summer and, thus, mean annual temperature shifts (Buziert et al 2018;Salonen et al 2018). Asynchronous warming over Greenland is attributed to reorganization of Atlantic meridional overturning circulation, freshwater forcing and atmospheric CO 2 dynamics (Buizert 2015;Buziert et al 2018).…”

“…Such records from the terrestrial realm are thus a prerequisite to document the spatio-temporal phase relations of seasonal temperature over the large geographical realm undergoing rapid climate change, after oceanic and/or atmospheric reorganizations. Decoupling of seasonal temperatures during other geological periods which may serve as potential analogues for present climate change, such as the Eemian interglacial, has recently been highlighted by proxy-based temperature reconstructions, where the mixed imprints of insolation and oceanic forcing regulates seasonality expression in the high northern Latitudes (Salonen et al 2018). The link to potential CO 2 forcing during the Eemian, however is low.…”

Chironomid-based temperature reconstruction for the Eemian Interglacial (MIS 5e) at Sokli, northeast Finland

“…The model relies on an age for the start of interglacial conditions at Sokli, as established by pollen, of 130.9 kyr BP (2517 cm) and an age for the end of the Eemian at Sokli of 117.5 kyr BP (1585 cm, in a parallel core not analyzed for chironomids) and assumes constant sedimentation rates between these points. The chronology presented by Salonen et al (2018) and used in this study differs from the previously published chronology for the Eemian at Sokli, which was based on land-sea comparison (Helmens et al 2015), by establishing an earlier onset of interglacial conditions at Sokli. .…”

“…An age model for the Eemian lacustrine sequence based on correlation with other regional and global events has been developed by Salonen et al (2018). The model relies on an age for the start of interglacial conditions at Sokli, as established by pollen, of 130.9 kyr BP (2517 cm) and an age for the end of the Eemian at Sokli of 117.5 kyr BP (1585 cm, in a parallel core not analyzed for chironomids) and assumes constant sedimentation rates between these points.…”

“…We apply three independent chironomidclimate calibration datasets to the record to quantitatively reconstruct paleotemperatures during the Last Interglacial. The results are evaluated through comparison with previously published multiproxy paleolimnological data and a pollen-based temperature reconstruction from the same site (Salonen et al 2018). Comparisons are also made with Eemian Interglacial climate records from central Europe and the North Atlantic Ocean in order to analyze spatial variability in Eemian climate dynamics and to discuss potential drivers of past climate change.…”