Climate models have been making significant progress encompassing an increasing number of complex feedback mechanisms from natural ecosystems. Permafrost thaw and subsequent induced greenhouse gas emissions, however, remain a challenge for climate models at large. Deducing permafrost conditions and associated greenhouse gas emissions from parameters that are simulated in climate models would be a helpful step towards estimating emission budgets from permafrost regions. Here we use a regional climate model with a 5 km horizontal resolution to assess future potential methane (CH 4 ) emissions over presently unglaciated areas in Greenland under an RCP8.5 scenario. A simple frost index is applied to estimate permafrost conditions from the model output. CH 4 flux measurements from two stations in Greenland; Nuuk representing sub-Arctic and Zackenberg high-Arctic climate, are used to establish a relationship between emissions and near surface air temperature. Permafrost conditions in Greenland change drastically by the end of the 21st century in an RCP8.5 climate. Continuous permafrost remains stable only in North Greenland, the north-west coast, the northern tip of Disko Island, and Nuussuaq. Southern Greenland conditions only sustain sporadic permafrost conditions and largely at high elevations, whereas former permafrost in other regions thaws. The increasing thawed soil leads to increasing CH 4 emissions. Especially the area surrounding Kangerlussuaq, Scoresby Land, and the southern coast of Greenland exhibit potentially high emissions during the longer growing season. The constructed maps and budgets combining modelled permafrost conditions with observed CH 4 fluxes from CH 4 promoting sites represent a useful tool to identify areas in need of additional monitoring as they highlight potential CH 4 hot spots.
<p>What determines the character of glacial inceptions? Does the spatio-temporal pattern of ice nucleation and expansion vary much between Late Pleistocene glacial inceptions? According to various benthic del18O stacks, the MIS 7 interglacial was the most anomalous in character of the last 4 interglacials. Key differences include a weaker interglacial state and an initial fast inception interrupted by a return to a similar and extended interglacial state. These anomalies of MIS 7 along with temporal proximity arguably make the last two glacial inceptions the best test case for addressing our opening questions. As part of a larger project to generate and analyze a data-constrained ensemble of fully coupled ice/climate transient simulations for the last two complete glacial cycles, herein we present initial results comparing the last two glacial inceptions (MIS 7 and 5d). We are using a new version of the fully coupled ice/climate model LCice. LCice now simulates all 4 paleo ice sheet complexes with hybrid shallow-shelf and shallow-ice physics. It has already been shown to capture northern hemispheric ice sheet growth and subsequent retreat consistent with inferences from global mean sea level proxies (Bahadory et al, 2019). Orbital and greenhouse gas changes are the only external forcings applied to the model. A 300 member ensemble probes parametric uncertainties in both the 3D Glacial Systems Model and LoveClim (Atmosphere/Ocean/Vegetation) components of LCice. Our presentation will compare the evolution and relative phasing of all 4 paleo ice sheets, and associated changes in the rest of the modelled climate system.</p>
<p>Paleo records indicate significant variation in sea level and temperature proxies between different glacial cycles. What is unclear is the extent to which these differences are due to noise in the physical system versus a robust response to external forcings. When one considers what is happening with each individual ice sheet, variations between glacial cycles are largely unknown, given the few relevant records available to constrain ice sheet extent before the Eemian.&#160;</p> <p>To explore both the controls on past ice sheet and climate evolution and explore bounds on what the evolution might actually have looked like, we are running ensemble simulations of the last two glacial cycles with the fully coupled ice/climate model LCice. LCice is a coupled version of the Loveclim EMIC and GSM glacial systems model with hybrid shallow shelf and shallow ice flow and global visco-elastic glacio-isostatic adjustment. The current configuration includes all 4 ice sheet complexes and is subject to only orbital and greenhouse gas forcing.</p> <p>To answer the above questions, we present ensemble results for the last two glacial inceptions, focusing on what key ice sheet and climate characteristics are robust across the ensemble and what are not. The role of key forcings and feedbacks are also isolated through a set of sensitivity experiments.&#160;&#160;</p>
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