Global Data Gaps in Our Knowledge of the Terrestrial Cryosphere

Hamish D Pritchard

doi:10.3389/fclim.2021.689823

Abstract

The IPCC Special Report on Oceans and Cryosphere in a Changing Climate identified major gaps in our knowledge of snow and glacier ice in the terrestrial cryosphere. These gaps are limiting our ability to predict the future of the energy and water balance of the Earth's surface, which in turn affect regional climate, biodiversity and biomass, the freezing and thawing of permafrost, the seasonal supply of water for one sixth of the global population, the rate of global sea level rise and the risk of riverine and coastal flooding. Snow and ice are highly susceptible to climate change but although their spatial extents are routinely monitored, the fundamental property of their water content is remarkably poorly observed. Specifically, there is a profound lack of basic but problematic observations of the amount of water supplied by snowfall and of the volume of water stored in glaciers. As a result, the climatological precipitation of the mountain cryosphere is, for example, biassed low by 50–100%, and biases in the volume of glacier ice are unknown but are likely to be large. More and better basic observations of snow and ice water content are urgently needed to constrain climate models of the cryosphere, and this requires a transformation in the capabilities of snow-monitoring and glacier-surveying instruments. I describe new solutions to this long-standing problem that if deployed widely could achieve this transformation.

Highlights

The IPCC Special Report on Oceans and Cryosphere in a Changing Climate (SROCC) highlighted key strengths and weaknesses in our understanding of the cryosphere (IPCC, 2019)
The factor is 1.55 annually in the High Mountain Asia (HMA) (1.90 in winter and 1.44 in summer), 1.5–2 annually throughout the Arctic, and up to 2.05 for the Andes in winter (Figure 2B). Such biases among mountains are present in comparable gridded precipitation products produced by various methods, including PREC/L (Chen et al, 2002), CHELSA V1.2, CHPclim V1, GPCC V2015, GPCP V2.3, and MERRA-2 (Beck et al, 2020), and regional hydrological assessments (e.g., Wortmann et al, 2018; Pritchard, 2019). These bias corrections have been calculated, they apply only to climatological averages and not the daily timescales of weather models, and have considerable uncertainty due to the challenges involved in calibrating precipitation from streamflow: the range in possible correction factors in the Andes locally exceeds 4.00 (Figure 2C)
The thickness of mountain glaciers is much less well-surveyed than that of the ice sheets (Pritchard, 2014) and projections of future mass-loss are highly sensitive to the initial ice volume (Hanna et al, 2020)

Summary

Introduction

The IPCC Special Report on Oceans and Cryosphere in a Changing Climate (SROCC) highlighted key strengths and weaknesses in our understanding of the cryosphere (IPCC, 2019). Global glacier mass loss was as great as that from the Greenland Ice Sheet (the single largest source of sea level rise), but with 10fold greater uncertainty (Figure 1).

Results

Conclusion