Scenarios for regional sea level rise along the North Sea

Post date: Oct 24, 2014 7:50:12 PM

2014/10/24. Sea level rises as our climate gradually warms. Not only the oceans expand, also their circulations may change. Glaciers, already on retreat in most areas, will further melt as the global temperature rises. Even the largest ice sheets are on the brink of facing big changes. Partly as a basic consequence of the second law of Newton (mass attracts mass), and partly because of more complicated effects, the sea level rise will not be uniform around the globe (see Figure below). In our paper, which has just been accepted for publication in ERL (Environmental Research Letters), we detail the consequences for the Netherlands, by constructing two scenarios for two temperature pathways. We find regional scenarios that (for the Dutch coast, see second figure) are rather similar to those obtained for the global mean. However upon comparing different contributions, differences can be found. Abstract follows below. The link to the special issue of ERL where more KNMI scenario work will appear is here

Fig caption. Median of projected sea-level rise (in cm) in 2085 for the "W" temperature scenario which is +3.5C above the temperature of the reference period (1986-2005). As one can see, near the Ice Sheets, the projected change is substantially lower than the global mean. Source: KNMI.

Figure caption: Scenarios for sea-level rise along the North Sea coast. The vertical axis denotes 30-year running mean sea-level change in cm, relative to 1986-2005. For years before 2000 and beyond 2085, the mean was taken over an increasingly smaller window and is drawn in a different shading. Estimates of natural variability at 5-year time-scale (see text for details) is included in the range and shown as vertical dashes. The black line denotes the 30-year running mean through tide-gauge observations along the Dutch coast, grey + symbols the 5-year running means (see text for details). The green x symbols show 5-year running means from satellite altimetry over the North Sea, with respect to 1993-1997 mean. The right margin shows the ranges from the different processes in 2100. Source: ERL paper.

Abstract: "The effects of sea level change become increasingly relevant for the Dutch coast. Therefore we construct two scenarios for regional sea-level change in the 21st century. They are designed to follow two temperature pathways, in which global mean temperature rises moderately ("G", +1.5K in 2085) or more substantially ("W", +3.5K in 2085). Contributions from all major processes leading to sea level rise are included (ocean expansion, glacier melt, ice-sheet changes, and landwater changes), except glacial isostatic adjustment and surface elevation changes. As input we use data from 42 coupled global climate models that contributed to CMIP5. The approach is consistent with the recent Fifth Assessment Report of IPCC, but provides an alternative viewpoint based on global temperature changes rather than RCPs. This makes them rather accessible and readily applicable to policy makers and the general public. We find a likely range for the G-scenario of +25--60 cm in 2085, and +45--80 cm for the W-scenario. These numbers have been rounded to 5 cm precision, to emphasise to any end-user of these scenarios that estimated lower and upper limits themselves are uncertain."