Global sea level rise is one of the most distinct signs of a warming climate. The main causes for
rising sea levels are the warming of the oceans and the resulting thermal expansion as well as the
melting of glaciers and ice sheets. It is, however, the regional sea level changes that have serious
consequences for the coastal population, infrastructure and economy, and that are therefore of great
interest.
Regional sea level changes may deviate greatly from the global mean simulations with complex
climate models are necessary to understand them. Combined with estimates of future emissions, so-
called scenarios, such models are used to project regional sea level changes. Scenarios describe the
expected evolution of human-related greenhouse gas emissions and aerosols as well as changes in
land use and ozone concentration. The exact future evolution of those forcings is unknown.
Therefore, to estimate the range of possible sea level changes, it is necessary to run climate models
for a large number of scenarios yet, this is an expensive and time consuming undertaking.
Recent research revealed that regional sea level changes follow a spatial pattern, the strength of
which can be derived from e.g. global mean surface temperature a variable that is relatively easy
to model. For coastal communities this would provide the possibility to estimate the range of
possible future sea level change relatively easily and to take action in time to prevent damage.
However, before the spatial patterns can be used for such practical purposes, it is important to
understand what causes them, what the underlying physical processes are and whether the patterns
are robust and therefore reliable. These are the questions we want to answer in our research project.
To do so, we will make use of the numerous existing model simulations of the climate of the past
150 years and investigate how the various forcing agents (e.g. greenhouse gases, aerosols or ozone)
affect regional sea level change. How can we distinguish between the individual forcings? We will
use dedicated climate simulations that are performed with selected forcings only. It is possible to
force a climate model with volcanic eruptions only. Or with greenhouse gas emissions. By doing
so, the effect of a single forcing on the climate system in general and sea level in particular can be
estimated. Our goal is to identify a distinct spatial pattern that can be attributed to each forcing
agent individually for each of the major contributors to sea level change (e.g. ocean warming and
glaciers). We will also analyze how these patterns depend on the magnitude of the forcings. The
forcing-specific response patterns can then be used to easily project regional sea level changes for a
large number of future scenarios.