Large uncertainties in high-end regional sea level rise projections due to skewness in dynamical ice sheet contribution.

Abstract:

In the 5^thIPCC assessment report uncertainties in sea level rise projections are Gaussian distributed. Recent assessments indicate that the probability distribution of the contribution of ice sheet mass loss may well be distributed asymmetrically towards higher projections. In this study we present the consequence of this asymmetry for high-end regional sea level projections. These estimates include gravitational and rotational effects as well as variability caused directly by climate change.

Results show that the global average 95% confidence interval for sea level shifts to 26 cm higher values, compared to symmetrical distribution based on the IPCC AR5 report. Regionally both lower (near ice sheets) and higher values (more than 60 cm for the east coast US for the 95% confidence interval) are possible depending on the location with respect to ice loading changes. Results diverge even more for higher confidence levels and hence this effect is of large importance for coastal defences as flood risks may increase considerably.