Coupling framework (1.0) for the ice sheet model PISM (1.1.1) and the ocean model MOM5 (5.1.0) via the ice-shelf cavity module PICO

Abstract

Abstract. The past and future evolution of the Antarctic Ice Sheet is largely controlled by interactions between the ocean and floating ice shelves. To investigate these interactions, coupled ocean and ice sheet model configurations are required. Previous modelling studies have mostly relied on high resolution configurations, limiting these studies to individual glaciers or regions over short time scales of decades to a few centuries. We present a framework to couple the dynamic ice sheet model PISM with the global ocean general circulation model MOM5 via the ice-shelf cavity module PICO. Since ice-shelf cavities are not resolved by MOM5, but parameterized with the box model PICO, the framework allows the ice sheet and ocean model to be run at resolution of 16 km and 3 degree, respectively. This approach makes the coupled configuration a useful tool for the analysis of interactions between the entire Antarctic Ice Sheet and the Earth system over time spans on the order of centuries to millennia. In this study we describe the technical implementation of this coupling framework: sub-shelf melting in the ice sheet model is calculated by PICO from modeled ocean temperatures and salinities at the depth of the continental shelf and, vice versa, the resulting mass and energy fluxes from the melting at the ice-ocean interface are transferred to the ocean model. Mass and energy fluxes are shown to be conserved to machine precision across the considered model domains. The implementation is computationally efficient as it introduces only minimal overhead. The framework deals with heterogeneous spatial grid geometries, varying grid resolutions and time scales between the ice and ocean model in a generic way, and can thus be adopted to a wide range of model setups.

Interacting tipping elements increase risk of climate domino effects under global warming

“…The tipping elements in the Earth system are not isolated systems; they interact on a global scale (Lenton et al, 2019;Kriegler et al, 2009). These interactions could have stabilising or destabilising effects, increasing or decreasing the probability of emerging tipping cascades, and it remains an important problem to understand how the interactions between the tipping elements affect the overall stability of the Earth system.…”

“…Furthermore, the interactions between tipping elements have only partially been described in a framework of more conceptual (but process-based) models, and our current understanding of the interaction structure of tipping elements is partly based on expert knowledge. For a subset of five tipping elements, an expert elicitation was conducted that synthesised a causal interaction structure and an estimation for the probability of tipping cascades to emerge (Kriegler et al, 2009). These studied tipping elements were the Greenland Ice Sheet, the West Antarctic Ice Sheet, the Atlantic Meridional Overturning Circulation (AMOC), the El Niño-Southern Oscillation (ENSO) and the Amazon rainforest (see Figs.…”

“…Although this network is not complete with respect to the physical interactions between the tipping elements and the actual set of tipping elements themselves (Wang and Hausfather, 2020;Lenton et al, 2019;Steffen et al, 2018), it presented a first step towards synthesising the positive and negative feedbacks between climate tipping elements. To the best of our knowledge, a systematic update of this assessment or a comparably comprehensive ex-pert assessment has not been undertaken since Kriegler et al (2009). Based on the network from this expert elicitation and a Boolean approach founded on graph grammars, an earlier study found that the strong positive-negative feedback loop between the Greenland Ice Sheet and the AMOC might act as a stabiliser to the Earth system (Gaucherel and Moron, 2017).…”

“…Based on the network from this expert elicitation and a Boolean approach founded on graph grammars, an earlier study found that the strong positive-negative feedback loop between the Greenland Ice Sheet and the AMOC might act as a stabiliser to the Earth system (Gaucherel and Moron, 2017). Also, using the interaction network data of Kriegler et al (2009), it has been shown that large economic damages due to tipping cascades could arise with respect to the social cost of carbon, using a stochastic and dynamic evaluation of tipping points in an integrated assessment model (Cai et al, 2016). Other studies also quantified the economic impacts of single climate tipping events and tipping interactions (Lemoine and Traeger, 2016;Cai et al, 2015).…”

“…Interactions between climate tipping elements and their roles in tipping cascades. The Greenland Ice Sheet, the West Antarctic Ice Sheet, the Atlantic Meridional Overturning Circulation (AMOC) and the Amazon rainforest are depicted along with their main interactions (Kriegler et al, 2009). The links between the tipping elements are colour coded, where red arrows depict destabilising and blue arrows depict stabilising interactions.…”