Abstract
Abstract. Although the Last Interglacial (LIG) is often considered as a possible analogue for future climate in high latitudes, its precise climate evolution and associated causes remain uncertain. Here we compile high-resolution marine sediment records from the North Atlantic, Labrador Sea, Norwegian Sea and the Southern Ocean. We document a delay in the establishment of peak interglacial conditions in the North Atlantic, Labrador and Norwegian Seas as compared to the Southern Ocean. In particular, we observe a persistent iceberg melting at high northern latitudes at the beginning of the LIG. It is associated with (1) colder and fresher surface-water conditions in the North Atlantic, Labrador and Norwegian Seas, and (2) a weaker ventilation of North Atlantic deep waters during the early LIG (129–125 ka) compared to the late LIG. Results from an ocean-atmosphere coupled model with insolation as a sole forcing for three key periods of the LIG show warmer North Atlantic surface waters and stronger Atlantic overturning during the early LIG (126 ka) than the late LIG (122 ka). Hence, insolation variations alone do not explain the delay in peak interglacial conditions observed at high northern latitudes. Additionally, we consider an idealized meltwater scenario at 126 ka where the freshwater input is interactively computed in response to the high boreal summer insolation. The model simulates colder, fresher North Atlantic surface waters and weaker Atlantic overturning during the early LIG (126 ka) compared to the late LIG (122 ka). This result suggests that both insolation and ice sheet melting have to be considered to reproduce the climatic pattern that we identify during the early LIG. Our model-data comparison also reveals a number of limitations and reinforces the need for further detailed investigations using coupled climate-ice sheet models and transient simulations.
Highlights
The Last Interglacial (LIG) period (129–118 ka, 1 ka = 1000 years) is termed Marine Isotope Stage 5.5 (MIS 5.5) in marine sediment cores or Eemian in European continental records (e.g. Kukla et al, 1997, 2002)
First we investigate the geographical polar extension of the late thermal optimum recorded in Norwegian Sea surface waters during the LIG and its potential counterpart in deep waters
This study confirms the extremely high freshwater flux computed in our study. It shows with “more realistic” freshwater values the similar impact of northern ice sheet melting on North Atlantic climate that we report at the beginning of the LIG
Summary
Kukla et al, 1997, 2002) This period is characterized by a high-latitude climate warmer by several degrees than today (North Greenland Ice Core Project members, 2004; Cape Last Interglacial Project members, 2006; EPICA Community members, 2006; Clark and Huybers, 2009). Given its high insolation forcing, the LIG is generally regarded as a potential analogue for future climate evolution High southern latitudes exhibit high temperatures as early as 11.7 ka in the Southern Ocean (e.g. Calvo et al, 2007; Skinner et al, 2010) and over Antarctica (e.g. EPICA Community members, 2006; Stenni et al, 2011). Sea level rose ca. 60 m during the early Holocene until 7 ka when the Holocene sea level highstand was reached (e.g. Smith et al, 2011 for a review)
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