Aslak Grinsted1, Jonathan Bamber2,3,
Rory Bingham2, Sammie Buzzard4,
Isabel Nias5, Kelvin Ng6, Jennifer
Weeks7
1Physics of Ice, Climate, and Earth, Niels Bohr
Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark2School of Geographical Sciences, University of
Bristol, Bristol, BS8 1SS, UK3Department of Aerospace and Geodesy, Data Science in
Earth Observation, Technical University of Munich, Munich, Germany4School of Earth and Environmental Sciences, Cardiff
University, Cardiff, UK5School of Environmental Sciences, University of
Liverpool, Liverpool, L69 7ZT, UK6School of Geography, Earth and Environmental
Sciences, University of Birmingham, Birmingham B15 2TT, UK7Met Office, Exeter, EX1 3PB, UK
Corresponding author: Jonathan Bamber
(j.bamber@bristol.ac.uk)
Key Points:
- The rate of ice sheet mass loss and ocean expansion has a near linear
relationship to global mean surface warming in both models and data.
- The modeled transient sensitivity of the sea level budget to warming
is compatible with historical behavior except for Antarctic mass loss.
- Models of Antarctic mass loss may be biased as data shows increasing
losses with warming in contrast to models.
Abstract
Earth is warming and sea levels are rising as land-based ice is lost to
melt, and oceans expand due to accumulation of heat. The pace of ice
loss and steric expansion is linked to the intensity of warming. How
much faster sea level will rise as climate warms is, however, highly
uncertain and difficult to model. Here, we quantify the transient sea
level sensitivity (TSLS) of the sea level budget in both models and
observations. Models show little change in sensitivity between the first
and second half of the 21st century for most
contributors. The exception is glaciers and ice caps (GIC) that have a
greater sensitivity pre-2050 (2.8±0.4 mm/yr/K) compared to later
(0.7±0.1 mm/yr/K). We attribute this change to the short response time
of glaciers and their changing area over time. Model sensitivities of
steric expansion (1.5±0.2 mm/yr/K), and Greenland Ice Sheet mass loss
(0.8±0.2 mm/yr/K) are greater than, but still compatible with,
corresponding estimates from historical data (1.4±0.5 mm/yr/K and
0.5±0.1 mm/yr/K). Antarctic Ice Sheet (AIS) models tends to show lower
rates of sea level rise with warming (‑0.0±0.3 mm/yr/K) in contrast to
historical estimates (0.4±0.2 mm/yr/K). This apparent low bias in AIS
sensitivity is only partly able to account for a similar low bias
identified in the sensitivity of GMSL excluding GIC (3.2±0.5 mm/yr/K vs
2.2±0.4 mm/yr/K). The balance temperature, where sea level rise is zero,
lies close to the pre-industrial value, implying that sea level rise can
only be mitigated by substantial global cooling.