Hydrosphere

DTU Space analyzes water level data from both satellites in space and measuring stations on land. It provides knowledge of previous changes in sea level as well as insight into the current rise. The rise in sea level is an important parameter in the analysis of climate change and their impact on seas and ice caps in Greenland, the Arctic, and in Antarctica. When the ice caps melt, the bedrock beneath rises. When using measuring stations on land, it is important to determine how much the bedrock rises. Only in this way we can accurately measure the real rise in sea level obtained.

Contact

Ole Baltazar Andersen

Ole Baltazar Andersen Professor

Per Knudsen

Per Knudsen Professor

Karina Nielsen

Karina Nielsen Senior Researcher

Carsten Bjerre Ludwigsen

Carsten Bjerre Ludwigsen Postdoc

Peder Heiselberg

Peder Heiselberg PhD student

Tadea Veng

Tadea Veng PhD student

Linda Christoffersen

Linda Christoffersen PhD student

Bjarke Nilsson

Bjarke Nilsson PhD Student

DTU Space monitors the sea level in the oceans around Greenland using measuring stations in Thule, Nuuk, Qaqortoq (Julianehåb) and in Ittoqqrtoormiit (Scoresbysund). The stations are part of a global network that aims to collect information on water level changes for international monitoring programs PSMSL, IOC and Sonel.

DTU Space also uses measurements of the height of the sea surface to determine models for variations in the water level in the oceans. These variations are due to, among other things, tides and changes in the location of ocean currents. In the Pacific Ocean currents associated with el-niño can also be determined.

DTU Space also uses satellite measurements of the Earth's gravitational field to make models of the global ocean currents which to a large extent are governing the entire Earth's climate system.

The goal is to create better ocean models, which will partly lead to better predictions of storm surges for the benefit of shipping and partly to better climate models. Among other things, DTU Space has contributed to ESA's now completed satellite mission GOCE with the development of methods for using its gravity measurements in the determination of ocean currents.

Examples of our research in this field:

  • Acceleration sea level, hydro: We have determined recent sea level acceleration using independent ESA satellites (Veng and Andersen, 2021). We are collaboration with NASA sea level team and particularly professor Steve Nerem on the use of machine learning.
  • Altimetry for in-land waters: We have developed a novel approach to combine surface elevations from several missions, including repeat and a geodetic orbit, to achieve a water level time series with an increased temporal resolution. The surface elevations as a functions of 1-D space (distance along the river) and time are combined via a state-space model that accounts for river slope, inter mission bias, and a potential variable water level amplitude along the river. Water level time series with a high temporal resolution is essential for subsequent river discharge estimation.

With the launch of ICESat-2 it is now possible to map even the smallest water bodies in the most challenging topography using its high resolution laser altimeter. We use these data to examine ocean surface characteristics, derive very accurate inland water levels, map the surrounding topography of mountainous rivers, and a method has been developed for extracting shallow water bathymetry.