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

Abstract

Coupled Model Intercomparison Project phase 5 (CMIP5) climate models simulate a wide range of historical sea ice areas. Even models with areas close to observed values may contain compensating errors, affecting reliability of their projections. This study focuses on the seasonal cycle of sea ice, including analysis of model concentration budgets. Many models have insufficient autumn ice growth, leading to large winter biases. A subset of models accurately represent sea ice evolution year‐round. However, comparing their winter ice concentration budget to observations reveals a range of behaviors. At least one model has an accurate ice budget, which is only possible due to realistic ice drifts. The CMIP5 generation of model physics and resolution is therefore structurally capable of accurately representing processes in Antarctic sea ice. This implies that substantially improved projections of Antarctic dense ocean water formation and ice sheet melting are possible with appropriate subsetting of existing climate models.

Do Multi‐Model Ensembles Improve Reconstruction Skill in Paleoclimate Data Assimilation?

“…Specifically, for several target models (CSIRO, MPI), there is largest improvement over the mid‐ and high‐latitude Southern Ocean. In these regions there are few nearby observations and models tend to disagree on locations of frontal regions (e.g., Beadling et al., 2019; Holmes et al., 2019). For reconstructions of other target models, the lower error in the MME reconstructions is less focused over the high‐latitude southern hemisphere (Figure 2).…”

Discovery of new colonies by Sentinel2 reveals good and bad news for emperor penguins

“…Predictions of sea ice loss (Turner et al 2013) and other impacts of climate change, such as increases in temperature, fluctuations in precipitation, variation in ocean circulation and increased wind speed and storminess are likely to impact the whole sea ice ecosystem (Cavanagh et al 2017). Climate model simulations project sea ice retreat over the latter part of this century, but the amount and pattern of retreat remains difficult to assess (Holmes et al 2019). Regardless of GHG emissions scenario, there is therefore an ongoing need to monitor the population size and distribution of this sentinel species.…”

Non‐additive response of the high‐latitude Southern Hemisphere climate to aerosol forcing in a climate model with interactive chemistry

“…However, the CMIP5 generation of coupled atmosphere–ocean climate models (including the Met Office UM) have an established weakness in their dynamic simulation of Antarctic sea ice (i.e. Turner et al ., 2013; Holmes et al ., 2019). With a focus on Antarctic climate and surface circulation, our a priori expectation was that controlling the sea ice extent was more important for our results than the response of SSTs to GHG forcing.…”