A Synergistic Approach for Evaluating Climate Model Output for Ecological Applications

Abstract

Increasing concern about the impacts of climate change on ecosystems is prompting ecologists and ecosystem managers to seek reliable projections of physical drivers of change. The use of global climate models in ecology is growing, although drawing ecologically meaningful conclusions can be problematic. The expertise required to access and interpret output from climate and earth system models is hampering progress in utilizing them most effectively to determine the wider implications of climate change. To address this issue, we present a joint approach between climate scientists and ecologists that explores key challenges and opportunities for progress. As an exemplar, our focus is the Southern Ocean, notable for significant change with global implications, and on sea ice, given its crucial role in this dynamic ecosystem. We combined perspectives to evaluate the representation of sea ice in global climate models. With an emphasis on ecologically-relevant criteria (sea ice extent and seasonality) we selected a subset of eight models that reliably reproduce extant sea ice distributions. While the model subset shows a similar mean change to the full ensemble in sea ice extent (approximately 50% decline in winter and 30% decline in summer), there is a marked reduction in the range. This improved the precision of projected future sea ice distributions by approximately one third, and means they are more amenable to ecological interpretation. We conclude that careful multidisciplinary evaluation of climate models, in conjunction with ongoing modeling advances, should form an integral part of utilizing model output.

Myctophid Fish (Family Myctophidae) Are Central Consumers in the Food Web of the Scotia Sea (Southern Ocean)

“…The Scotia Sea -Antarctic Peninsula region has experienced rapid climate-related change over recent decades including increases in sea surface temperature (Meredith and King, 2005;Whitehouse et al, 2008) and reductions in sea ice extent (Stammerjohn et al, 2008;Turner et al, 2015). Climate models suggest that further warming and sea ice loss is likely during the current century (Hill et al, 2013;Cavanagh et al, 2017). Antarctic krill is a stenothermic species, but its distribution in this region extends north of 55 • S, where present temperatures are already close to its thermal limits for growth .…”

Observations and models to support the first Marine Ecosystem Assessment for the Southern Ocean (MEASO)

“…Figure 5 illustrates how the different system models described in Table 5 might fit together in a nested, ensemble of models. While not all the available models described in Table 5 will be used in the initial MEASO, the aim will be to utilise scenarios of environmental change from Earth System models (Cavanagh et al 2017), along with time-series of observations of physics, chemistry and biology, to drive regional food web and/or species models. These latter models can then be used to investigate the consequences, and their likelihoods, of the different scenarios on different parts of the ecosystem (see, for example, Klein et al 2018).…”

“…Earth System models can provide the state of habitat variables and primary producers across the Southern Ocean, although sea ice may not be well described at present (Cavanagh et al 2017). The ability for these models to represent the actual state of the Southern Ocean can be assessed as to their fit to time series of ocean observations; the relative ability for representing reality is termed 'model skill'.…”

Compensating Biases and a Noteworthy Success in the CMIP5 Representation of Antarctic Sea Ice Processes

“…Over the seasonal cycle, it changes in area by a factor of 6 through highly coupled ice, atmosphere, and ocean processes. Variability and trends in ice extent are of major importance to regional climate (e.g., Turner, Bracegirdle, et al, 2013), ecosystems (e.g., Cavanagh et al, 2017;Jenouvrier et al, 2014), and near-surface atmospheric conditions across the continent (e.g., Krinner et al, 2014) which have implications for the mass balance of the ice sheet. Sea ice formation, transport, and melt play an important role in setting the salinity structure of the Southern Ocean, affecting global ocean circulation (e.g., Abernathey et al, 2016;Haumann et al, 2016).…”