Chapter 17: The future? Big questions about feedbacks between Anthropogenic change in the cryosphere and atmospheric chemistry

Anthropogenically driven changes in the cryosphere (mainly climate warming, but also land-use changes and increasing industrial and transportation activities) are changing how the cryosphere interacts with the atmosphere, which is, in turn, influencing the trajectory of further climate change. In particular, sea ice, snow, and permafrost exchange numerous climatically-active substances with the atmosphere, and the dramatic changes occurring in the distribution and physical-chemical characteristics of these ice environments have both regional and global implications. Some of these interactions are reasonably well understood, as documented in a number of the reviews in this book. However, many current and potential future feedbacks between the cryosphere and the atmosphere are very uncertain, and in some cases, even the net directions of the feedbacks are unknown. Big questions remain about, for example: how the rates of methane release versus oxidation are changing in warming marine and terrestrial environments; the contributions of cryospheric primary and secondary aerosols to global and regional atmospheric particle loads and cloud cover; whether, where, and when ecosystem changes are increasing or decreasing CO2 drawdown; and how changes in temperature and light interact in controlling chemical reactivity on ice surfaces, as well as driving adaptations in biological communities. Answering these questions will require not only hard work, but also creativity in conceiving and designing new research programs and developing new technologies. Particular challenges exist in developing robust, autonomous, in situ observation systems for deployment in harsh cryospheric environments and in integrating interdisciplinary information and ideas across wide time and space scales, from the molecular processes occurring at ice surfaces to the global climate system