Elastic and non-elastic Vertical Land Motion in the wider Arctic

Abstract:

For tide-gauge based sea level studies it is important to know vertical land motion (VLM) at tide-gauge locations i.e. in order to study contributions to sea level change or validate altimetric observations. Interpreting trends at the available Arctic tide gauges is however difficult because GNSS-sites with continuous VLM-timeseries are very limited in the Arctic region or have poor data quality. Due to the lack of VLM-data, Arctic Sea level studies often rely on a glacial isostatic adjustment (GIA)-only model (e.g. Henry, 2012), which implies that the elastic response from present-day ice loading is neglected.

A high-resolution ice model (2x2 km) for Arctic glaciers and Greenland Ice Sheet has been constructed from 2003-2015 to calculate yearly elastic VLM-rates in the wider Artic region (roughly north of 30N). The high resolution makes it possible to use the elastic VLM in both in the proximity of glacial ice change and in the far field (e.g. Northern Europe).

The elastic VLM-model is combined with a GIA-model and is corrected for non-secular geocenter motion effects, as well as rotational feedback, to construct a complete VLM-model that is comparable with yearly GNSS-measured VLM-rates. Furthermore, are far field elastic VLM-estimates from Antarctica added to the model (about -0.1 mm/y in the Arctic area).

Averaged over time, does the VLM-model correlate well with GNSS-sites - in particular in the far field and clearly outperforms a GIA-only model. Residuals between GNSS and the combined VLM-model is used to quantify the effect of ongoing seismic activity (Alaska), low-viscosity areas (Iceland) or ongoing rebound from Little Ice Age (Svalbard) on VLM.

Generally, it shows that VLM from present-day ice melt of in particular Greenland, is far-reaching and even in the North Sea region or along the North American coast show uplift rates in the order of 0.4-0.7 mm/y. Interestingly, this is comparable to Greenland’s sea level contribution for the same period, thereby is elastic VLM, in parts, 'neutralizing' the barystatic sea level contribution of Greenland and glaciers. As Arctic ice mass loss continues to accelerate, the elastic uplift will have increased importance for coastal regions and future relative sea level projections.