Impact of meltwater on high-latitude early Last Interglacial climate

Abstract

Abstract. Recent data compilations of the early Last Interglacial period have indicated a bipolar temperature response at 130 ka, with colder-than-present temperatures in the North Atlantic and warmer-than-present temperatures in the Southern Ocean and over Antarctica. However, climate model simulations of this period have been unable to reproduce this response, when only orbital and greenhouse gas forcings are considered in a climate model framework. Using a full-complexity general circulation model we perform climate model simulations representative of 130 ka conditions which include a magnitude of freshwater forcing derived from data at this time. We show that this meltwater from the remnant Northern Hemisphere ice sheets during the glacialinterglacial transition produces a modelled climate response similar to the observed colder-than-present temperatures in the North Atlantic at 130 ka and also results in warmer-thanpresent temperatures in the Southern Ocean via the bipolar seesaw mechanism. Further simulations in which the West Antarctic Ice Sheet is also removed lead to warming in East Antarctica and the Southern Ocean but do not appreciably improve the model-data comparison. This integrated modeldata approach provides evidence that Northern Hemisphere freshwater forcing is an important player in the evolution of early Last Interglacial climate.

The PMIP4 contribution to CMIP6 – Part 2: Two interglacials, scientific objective and experimental design for Holocene and Last Interglacial simulations

“…There is also evidence of a rapid sea-level rise associated with this meltwater pulse, estimated at ∼ 70 m or 28 ± 8 m ka −1 (∼ 0.32 ± 0.09 Sv) during the deglacial transition (Grant et al, 2012). Model simulations have shown that the freshwater forcing of H11, including its cessation, may be important for explaining the evolution of climate through the early part of the LIG (Goelzer et al, 2016a, b;Holden et al, 2010;Loutre et al, 2014;Stone et al, 2016). We propose a sensitivity experiment (lig127k-H11) to examine the impact of the H11 event.…”

“…In addition, the LIG provides an ideal opportunity to examine the role of cryosphere feedbacks through sensitivity experiments, which will be a focus of additional experiments associated with both the Holocene and the LIG. One such feedback is the release of freshwater into the ocean and the role of such freshwater forcing in generating more abrupt climate changes than would be expected for the smoothly varying changes in insolation forcing during an interglacial (Goelzer et al, 2016a;Luan et al, 2015;Stone et al, 2016). Understanding the role of feedbacks in general in the generation of abrupt climate changes, and the need to understand the relationship between mean climate changes , 2016).…”

Two Interglacials: Scientific Objectives and Experimental Designs for CMIP6 and PMIP4 Holocene and Last Interglacial Simulations

“…Model simulations have shown that the freshwater forcing of H11, including its cessation, may be important for explaining the evolution of climate through the early part of the LIG (Goelzer et al, 2016b;Holden et al, 2010;Loutre et al, 2014;Stone et al, 2016). We propose a sensitivity experiment to examine the impact of the H11 event.…”

“…In addition, the LIG provides an ideal opportunity to examine the role of cryosphere feedbacks through sensitivity experiments, which will be a focus of additional experiments associated with both the Holocene and the LIG. One such feedback is the release of freshwater into the ocean and the role of such freshwater forcing in generating more abrupt climate changes than would be expected for the smoothly varying changes in insolation 145 forcing during an interglacial (Goelzer et al, 2016a;Luan et al, 2015;Stone et al, 2016). Understanding the role of feedbacks in general on the generation of abrupt climate changes, and the need to understand the relationship between mean climate changes and short-term (annual to multi-decadal) climate variability, leads naturally to a desire to simulate the transient behavior of the climate system -and such transient experiments will be made for both the Holocene and LIG time periods.…”

“…limitation in using these two data sets for analysis of the lig127k simulations and associated sensitivity experiments is that they are compilations of information about the maximum warmth during the LIG. Given that warming was not synchronous globally (Bauch and Erlenkeuser, 2008;Cortese et al, 2007;Dahl-Jensen et al, 2013;Govin et al, 2012;Masson-Delmotte et al, 2010;Mor et al, 2012;Winsor et al, 2012), these syntheses do not represent a year long time slabs, and this approach has been expanded to include the fifth time slab (126-128 ka) for comparison with the lig127k simulation (Capron et al, 2016). However, even though these compilations are based on harmonized chronologies, dating uncertainties during the LIG can still be several thousand years depending on the type of archive and the dating methods (Govin et al, 2015).…”