Regional Sea Level Rise in the North Sea

Luciana Fenoglio-Marc (Technische Universität Darmstadt, Germany)


S. Dangendorf (University Siegen, Germany); M. Becker (TU Darmstadt, Germany); J. Jensen (University Siegen, Germany); T. Wahl (University Siegen, Germany)

Event: 2014 Ocean Surface Topography Science Team Meeting

Session: Science Results from Satellite Altimetry: Regional and basin-scale processes and sea level rise

Presentation type: Type Poster

The coastline of the North Sea is one of the most densely populated coasts in the world. The low-lying German and Dutch coasts are vulnerable to storm surges and long-term sea level change. An accurate estimate of the long-term trends in relative sea level is thus of primary importance.

In the present study we characterize sea level rise and variability from late 1900 to present using tide gauges, satellite altimetry, vertical land motion (VLM), atmospheric reanalyses, hydrographic profiles, and outputs from barotropic and baroclinic ocean models.

The relative sea level (RSL) fluctuations as measured by tide gauges include both absolute sea level changes and vertical land motions (VLM) due to glacial isostatic adjustment (GIA), tectonic processes, coastal subsidence or uplift. We derive the VLM rates by applying different approaches including GIA, geological information, CGPS, and differences between RSL and satellite altimetry. Surprisingly, we find that currently the most reliable estimate corresponds to the GIA models and to geological information, while the CGPS and altimetry estimates are rather uncertain due to the shortness of time series and inaccuracy of altimetry near coast. When applying the GIA correction the estimated absolute mean sea level (MSL) trend is 1.5 ± 0.1 mm/yr for 1900-2011, which is consistent with global means during the same period.

However, the MSL change is far from being linear and presents variations at time scales from months to several decades. We show that the atmospheric forcing plays a key role in characterizing these variability patterns and that the barotropic processes introduce rise rates of about 0.4 mm/yr. On longer timescales steric variations become more important. By comparing the spatial information given by altimetry with the outputs of baroclinic ocean models we show that steric variations are closely linked to long-shore winds along the eastern boundary of the Northeast Atlantic.

Summarizing we discuss various scientific challenges in the North Sea region. To get more confidence in regional SLR rates, longer CGPS and altimetry measurements and more detailed ocean models are required.

Luciana Fenoglio-Marc
Technische Universität Darmstadt