Observing and Modeling Ice Sheet Surface Mass Balance

Abstract

Surface mass balance (SMB) provides mass input to the surface of the Antarctic and Greenland Ice Sheets and therefore comprises an important control on ice sheet mass balance and resulting contribution to global sea level change. As ice sheet SMB varies highly across multiple scales of space (meters to hundreds of kilometers) and time (hourly to decadal), it is notoriously challenging to observe and represent in models. In addition, SMB consists of multiple components, all of which depend on complex interactions between the atmosphere and the snow/ice surface, large‐scale atmospheric circulation and ocean conditions, and ice sheet topography. In this review, we present the state‐of‐the‐art knowledge and recent advances in ice sheet SMB observations and models, highlight current shortcomings, and propose future directions. Novel observational methods allow mapping SMB across larger areas, longer time periods, and/or at very high (subdaily) temporal frequency. As a recent observational breakthrough, cosmic ray counters provide direct estimates of SMB, circumventing the need for accurate snow density observations upon which many other techniques rely. Regional atmospheric climate models have drastically improved their simulation of ice sheet SMB in the last decade, thanks to the inclusion or improved representation of essential processes (e.g., clouds, blowing snow, and snow albedo), and by enhancing horizontal resolution (5–30 km). Future modeling efforts are required in improving Earth system models to match regional atmospheric climate model performance in simulating ice sheet SMB, and in reinforcing the efforts in developing statistical and dynamic downscaling to represent smaller‐scale SMB processes.

Present‐Day Greenland Ice Sheet Climate and Surface Mass Balance in CESM2

“…At its upper surface boundary, CISM is forced by temperature and SMB as calculated in CLM. A common definition of SMB in glaciology reads (e.g., Lenaerts et al, ; van den Broeke et al, ): …”

Satellite Remote Sensing of the Greenland Ice Sheet Ablation Zone: A Review

“…The components of MB are commonly expressed in units of mass per time (e.g., kg yr −1 or Gt yr −1 ), mass per unit area per time (e.g., kg m −2 yr −1 ), and mass per unit area per time normalized by density of liquid water (e.g., m water equivalent, m w.e. yr −1 ) [21].…”

“…Ice sheets and glaciers gain mass through snowfall and lose mass through sublimation, meltwater runoff, and solid ice discharge. Following Lenaerts et al [21] and van den Broeke et al [60], the mass balance MB of an ice sheet is usually written as:…”

“…Such comparisons require accurate knowledge of the surface density and change in surface elevation due to ice dynamic motion, and, therefore, are most appropriate for bare ice areas during summer when surface melting dominates the elevation change signal [89]. Finally, it was recently reported that the CryoSat-2 science team is considering adjusting the satellite's orbit to overlap its ground tracks with those of ICESat-2 once everỹ 2 days [21]. If so, these overlapping data would provide cross-platform dH/dt validation and could be used to infer changes in the CryoSat-2 Ku-band penetration depth into snow and firn.…”

Effect of prescribed sea surface conditions on the modern and future Antarctic surface climate simulated by the ARPEGE atmosphere general circulation model

“…Projected 21st century increase in the Antarctic surface mass balance (SMB) due to higher snowfall rates is expected to partly compensate for eustatic sea-level rise (SLR) due to opposite changes in almost all other components affecting global sea level (Agosta et al, 2013;Ligtenberg et al, 2013;Lenaerts et al, 2016). However, the acceleration of ice flow and the interactions between oceans and ice shelves are expected to lead to an overall positive Antarctic contribution to SLR (Pollard et al, 2015;Ritz et al, 2015).…”