Mean sea‐level topography in the Baltic sea determined by oceanographic methods

1998 ◽  
Vol 21 (3) ◽  
pp. 203-217 ◽  
Author(s):  
Madleine Carlsson
2021 ◽  
Author(s):  
Ralf Weisse ◽  
Inga Dailidiene ◽  
Birgit Hünicke ◽  
Kimmo Kahma ◽  
Kristine Madsen ◽  
...  

Abstract. There are a large number of geophysical processes affecting sea level dynamics and coastal erosion in the Baltic Sea region. These processes operate on a large range of spatial and temporal scales and are observed in many other coastal regions worldwide. Together with the outstanding number of long data records, this makes the Baltic Sea a unique laboratory for advancing our knowledge on interactions between processes steering sea level and erosion in a climate change context. Processes contributing to sea level dynamics and coastal erosion in the Baltic Sea include the still ongoing visco-elastic response of the Earth to the last deglaciation, contributions from global and North Atlantic mean sea level changes, or from wind waves affecting erosion and sediment transport along the subsiding southern Baltic Sea coast. Other examples are storm surges, seiches, or meteotsunamis contributing primarily to sea level extremes. All such processes have undergone considerable variations and changes in the past. For example, over the past about 50 years, the Baltic absolute (geocentric) mean sea level rose at a rate slightly larger than the global average. In the northern parts, due to vertical land movements, relative sea level decreased. Sea level extremes are strongly linked to variability and changes in the large-scale atmospheric circulation. Patterns and mechanisms contributing to erosion and accretion strongly depend on hydrodynamic conditions and their variability. For large parts of the sedimentary shores of the Baltic Sea, the wave climate and the angle at which the waves approach the nearshore are the dominant factors, and coastline changes are highly sensitive to even small variations in these driving forces. Consequently, processes contributing to Baltic sea level dynamics and coastline change are expected to vary and to change in the future leaving their imprint on future Baltic sea level and coastline change and variability. Because of the large number of contributing processes, their relevance for understanding global figures, and the outstanding data availability, we argue that global sea level research and research on coastline changes may greatly benefit from research undertaken in the Baltic Sea.


2019 ◽  
Vol 32 (11) ◽  
pp. 3089-3108 ◽  
Author(s):  
Ulf Gräwe ◽  
Knut Klingbeil ◽  
Jessica Kelln ◽  
Sönke Dangendorf

Abstract We analyzed changes in mean sea level (MSL) for the period 1950–2015 using a regional ocean model for the Baltic Sea. Sensitivity experiments allowed us to separate external from local drivers and to investigate individual forcing agents triggering basin-internal spatial variations. The model reveals a basin-average MSL rise (MSLR) of 2.08 ± 0.49 mm yr−1, a value that is slightly larger than the simultaneous global average of 1.63 ± 0.32 mm yr−1. This MSLR is, however, spatially highly nonuniform with lower than average increases in the southwestern part (1.71 ± 0.51 mm yr−1) and higher than average rates in the northeastern parts (2.34 ± 1.05 mm yr−1). While 75% of the basin-average MSL externally enters the Baltic basin as a mass signal from the adjacent North Sea, intensified westerly winds and a poleward shift of low pressure systems explain the majority of the spatial variations in the rates. Minor contributions stem from local changes in baroclinicity leading to a basin-internal redistribution of water masses. An observed increase in local ocean temperature further adds to the total basinwide MSLR through thermal expansion but has little effect on the spatial pattern. To test the robustness of these results, we further assessed the sensitivity to six different atmospheric surface forcing reanalysis products over their common period from 1980 to 2005. The ensemble runs indicated that there are significant differences between individual ensemble members increasing the total trend uncertainty for the basin average by 0.22 mm yr−1 (95% confidence intervals). Locally the uncertainty varies from 0.05 mm yr−1 in the central part to up to 0.4 mm yr−1 along the coasts.


2016 ◽  
Vol 49 (1-2) ◽  
pp. 163-172 ◽  
Author(s):  
H. E. M. Meier ◽  
A. Höglund ◽  
K. Eilola ◽  
E. Almroth-Rosell

2021 ◽  
Vol 12 (3) ◽  
pp. 871-898
Author(s):  
Ralf Weisse ◽  
Inga Dailidienė ◽  
Birgit Hünicke ◽  
Kimmo Kahma ◽  
Kristine Madsen ◽  
...  

Abstract. There are a large number of geophysical processes affecting sea level dynamics and coastal erosion in the Baltic Sea region. These processes operate on a large range of spatial and temporal scales and are observed in many other coastal regions worldwide. This, along with the outstanding number of long data records, makes the Baltic Sea a unique laboratory for advancing our knowledge on interactions between processes steering sea level and erosion in a climate change context. Processes contributing to sea level dynamics and coastal erosion in the Baltic Sea include the still ongoing viscoelastic response of the Earth to the last deglaciation, contributions from global and North Atlantic mean sea level changes, or contributions from wind waves affecting erosion and sediment transport along the subsiding southern Baltic Sea coast. Other examples are storm surges, seiches, or meteotsunamis which primarily contribute to sea level extremes. Such processes have undergone considerable variation and change in the past. For example, over approximately the past 50 years, the Baltic absolute (geocentric) mean sea level has risen at a rate slightly larger than the global average. In the northern parts of the Baltic Sea, due to vertical land movements, relative mean sea level has decreased. Sea level extremes are strongly linked to variability and changes in large-scale atmospheric circulation. The patterns and mechanisms contributing to erosion and accretion strongly depend on hydrodynamic conditions and their variability. For large parts of the sedimentary shores of the Baltic Sea, the wave climate and the angle at which the waves approach the nearshore region are the dominant factors, and coastline changes are highly sensitive to even small variations in these driving forces. Consequently, processes contributing to Baltic sea level dynamics and coastline change are expected to vary and to change in the future, leaving their imprint on future Baltic sea level and coastline change and variability. Because of the large number of contributing processes, their relevance for understanding global figures, and the outstanding data availability, global sea level research and research on coastline changes may greatly benefit from research undertaken in the Baltic Sea.


Author(s):  
Ralf Weisse ◽  
Birgit Hünicke

A multitude of geophysical processes contribute to and determine variations and changes in the height of the Baltic Sea water surface. These processes act on a broad range of characteristic spatial and timescales ranging from a few seconds to millennia. On very long timescales, the northern parts of the Baltic are uplifting due to the still ongoing visco-elastic response of the Earth to the last deglaciation, and mean sea level is decreasing in these regions. Over centuries, the Baltic Sea responds to changes in global and North Atlantic mean sea level. Processes affecting global mean sea level, such as warming of the world ocean or melting of glaciers and of polar ice sheets, do have an imprint on Baltic Sea levels. Over decades, variations and changes in atmospheric circulation affect transport through the Danish Straits connecting the Baltic and North seas. As a result, the amount of water in the Baltic Sea and the height of the sea level vary. Similarly, atmospheric variability on shorter timescales down to a few days cause shorter period variations of transport through the Danish Straits and Baltic Sea level. On even shorter timescales, the Danish Straits act as a low pass filter, and high frequency variations of the water surface within the Baltic Sea such as storm surges, wind waves, or seiches are solely caused internally. All such processes have undergone considerable variations and changes in the past. Similarly, they are expected to show variations and changes in the future and across a broad range of scales, leaving their imprint on observed and potential future Baltic Sea level and its variability.


2018 ◽  
Vol 8 (6) ◽  
pp. 366-371 ◽  
Author(s):  
Magnus Hieronymus ◽  
Christian Dieterich ◽  
Helén Andersson ◽  
Robinson Hordoir

2015 ◽  
Vol 12 (1) ◽  
pp. 219-225 ◽  
Author(s):  
A. Lehmann ◽  
P. Post

Abstract. Salinity and stratification in the deep basins of the Baltic Sea are linked to the occurrence of Major Baltic Inflows (MBIs) of higher saline water of North Sea origin, which occur sporadically and transport higher saline and oxygenated water to deeper layers. Since the mid-1970s, the frequency and intensity of MBIs have decreased. They were completely absent between February 1983 and January 1993. However, in spite of the decreasing frequency of MBIs, there was no obvious decrease of larger Baltic Sea volume changes (LVCs). A LVC is defined by a total volume change of at least 100 km3. LVCs can be identified from the sea level changes at Landsort which is known to represent the mean sea level of the Baltic Sea very well. Strong inflows leading to LVCs are associated to a special sequence of atmospheric circulation patterns. Our analysis based on Jenkinson-Collison circulation (JCC) types confirms that most effective inflows occur if about a month before the main inflow period, eastern air flow with anticyclonic vorticity over the western Baltic prevails. These conditions reduce the mean sea level of the Baltic Sea and lead to an increased saline stratification in the Belt Sea area. An immediate period of strong to very strong westerly winds trigger the inflow and force LVCs/MBIs. The lack of MBIs coincide with a negative trend of eastern types and a parallel increase of western type JCCs.


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