Back to the Future: Using Long-Term Observational and Paleo-Proxy Reconstructions to Improve Model Projections of Antarctic Climate

Abstract

Quantitative estimates of future Antarctic climate change are derived from numerical global climate models. Evaluation of the reliability of climate model projections involves many lines of evidence on past performance combined with knowledge of the processes that need to be represented. Routine model evaluation is mainly based on the modern observational period, which started with the establishment of a network of Antarctic weather stations in 1957/58. This period is too short to evaluate many fundamental aspects of the Antarctic and Southern Ocean climate system, such as decadal-to-century time-scale climate variability and trends. To help address this gap, we present a new evaluation of potential ways in which long-term observational and paleo-proxy reconstructions may be used, with a particular focus on improving projections. A wide range of data sources and time periods is included, ranging from ship observations of the early 20th century to ice core records spanning hundreds to hundreds of thousands of years to sediment records dating back 34 million years. We conclude that paleo-proxy records and long-term observational datasets are an underused resource in terms of strategies for improving Antarctic climate projections for the 21st century and beyond. We identify priorities and suggest next steps to addressing this.

Interannual-to-Multidecadal Responses of Antarctic Ice Shelf–Ocean Interaction and Coastal Water Masses during the Twentieth Century and the Early Twenty-First Century to Dynamic and Thermodynamic Forcing

“…Kusahara and Hasumi (2013) conducted a series of idealized warming experiments and concluded that water masses flowing into ice shelf cavities differ greatly between Antarctic ice shelves and the changes in the inflowing water masses are responsible for the basal melt changes in the experiments. This study and all of the above studies clearly show that changes in coastal water masses over the Antarctic continental shelf are essential for understanding basal melt of Antarctic ice shelves, supporting the idea that the changes in Antarctic coastal water masses are one of the most important metrics for understanding Antarctic and Southern Ocean climates (Bracegirdle et al 2016).…”

“…Several studies have focused on the Antarctic iceocean interaction under present-day (i.e., the last few decades) and future conditions; however, no study has yet investigated the long-term evolution of the Southern Ocean ice-ocean interaction over the twentieth century. While the number of observations is limited in the beginning of the twentieth century, there exist some available observations and supporting evidence for the ocean and sea ice conditions in the Southern Ocean (Hobbs et al 2016b;Bracegirdle et al 2019). In other words, century-scale observational evidence, which consists of fragmented observations in the first half of the twentieth century and the more complete modern records, allows us to assess the model representation and performance.…”

Antarctic environmental change and biological responses

“…Since around 2000, the strong atmospheric warming trend along the Antarctic Peninsula has paused, although it is predicted to resume ( 11 ). Over the next century, the entire continent is expected to start to see climatic changes comparable to those recorded to date along the Antarctic Peninsula ( 12 , 13 ). The predicted “filling” of the ozone hole is likely to provide further positive feedback to this process.…”

Sea ice dynamics in the Bransfield Strait, Antarctic Peninsula, during the past 240 years: a multi-proxy intercomparison study

“…For modeling past and future Antarctic climate, ice sheet stability, the thermohaline circulation, or the impacts of sea ice loss for ecosystems, data on past sea ice cover are crucial although barely available (Bracegirdle et al, 2015(Bracegirdle et al, , 2019. For the WAP, insights into climate and sea ice dynamics during the past 200 years are available from ice cores (stable isotopes, marine aerosols and snow accumulation), but information from high-resolution marine sediments and in particular sedimentary, geochemical or diatom-based sea ice proxies remains sparse .…”