Antarctic climate and environment change over the next 100 years

Chapter Editor: Colin Summerhayes

Authors: David Barnes, Dana Bergstrom, Robert Bindschadler, James Bockheim, Laurent Bopp, Tom Bracegirdle, Steve Chown, Pete Convey, Guido di Prisco, Eberhard Fahrbach, Jaume Forcada, Yves Frenot, Hugues Goosse, Julian Gutt, Dominic Hodgson, Ad Huiskes, Anna Jones, Rebecca Leaper, Wouter Lefebvre, Andrew Lenton, Amanda Lynch, Nicolas Metzl, Alison Murray, Siobhan O’Farrell, Lloyd Peck, Hans Pörtner, Howard Roscoe, Daniel Smale, Victor Smetacek, Colin Summerhayes, John Turner, Ann Vanreusel, David Vaughan, Cinzia Verde, Zhaomin Wang

Introduction

Determining how the environment of the Antarctic will evolve over the next century presents many challenges, yet it is a question of great interest for both scientists and policymakers concerned with issues as diverse as sea-level rise and fish stocks. A major problem is that we still have a poor understanding of the mechanisms behind many of the changes observed in recent decades. This is particularly the case in the ocean where we have few long time series of physical measurements and remarkably few spatially and temporally well separated observations of marine biota.

The evolution of the Antarctic climate over the next 100 years can only be projected through the use of coupled atmosphere-ocean-ice models. These have their limits in correctly simulating the observed changes that have taken place already, so there is still a degree of uncertainty about the projections from models, particularly on the regional scale. The models used in the IPCC Fourth Assessment Report (AR4) (IPCC, 2007) gave a wide range of projections for some aspects of the Antarctic climate system. In the case of sea ice extent that was not entirely surprising, since this is very sensitive to changes in both atmospheric and oceanic conditions. The IPCC report took a mean estimate from 20 Atmosphere-Ocean General Circulation Models (AOGCMs) without regard to how individual models performed globally or regionally. The model projections for temperature and precipitation were used to estimate how much sea level would rise under various greenhouse gas emission scenarios. In the following pages we show how that 'blunderbuss approach' can be improved upon. With a quantity such as near-surface air temperature it is possible to use the projections from the various models to derive various estimates of how temperature may change over land and ocean.

The atmospheric component of the next generation of climate models must have interactive chemistry if we are to obtain meaningful projections of the future extent and thickness of the ozone layer over Antarctica, which will clearly impact future surface climate in Antarctica, as shown by Perlwitz et al. (2008).

An extremely important question for both scientists and policy makers, since it determines how sea level may change, is how the Antarctic ice sheet will change over coming decades. Models can estimate how the precipitation onto the continent might change, but the current generation of ice sheet models cannot help us regarding possible dynamical changes that might occur in the flow of glaciers and ice streams, or ocean-induced melting at the ice margin.

Gauging how Antarctic terrestrial and marine biota might respond to rising temperature is also a major challenge, as is gauging the response of ocean biota to ocean acidification. Some laboratory experiments have been carried out into the survival of biota when subject to thermal stress, as have field manipulations mimicking some predicted elements of climate change, but conditions in the Antarctic involve many complex feedbacks and interactions that cannot be well replicated under either approach. Furthermore, numerically based biological models cannot yet approach the relative sophistication of models of the physics of the climate system, while physical models do not approach the high level of spatial scale or temporal resolution required for application to biological systems, providing yet a further limitation on what can be said about future change in the context of biotic and ecosystem responses.

In this chapter we consider how the physical environment of the Antarctic might change over the next century, and assess how the biota may respond.

Pages in this topic

1. The IPCC fourth assessment report
2. Atmospheric change over the next 100 years
3. Ocean change over the next 100 years
4. Sea ice change over the 21st century
5. Changes to the Terrestrial cryosphere over the next 100 years
6. 21st century evolution of Antarctic permafrost
7. Antarctic and Southern Ocean sea level projections
8. The Southern Ocean carbon cycle response to future climate change
9. Biological responses to 21st climate climate change