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Mean sea level variability and influence of the North Atlantic oscillation on long-term trends in the German Bight

Mean sea level variability and influence of the North Atlantic oscillation on long-term trends in the German Bight
Mean sea level variability and influence of the North Atlantic oscillation on long-term trends in the German Bight
Changes in the seasonal cycle of mean sea level (MSL) may affect the heights of storm surges and thereby flood risk in coastal areas. This study investigates the intra- and inter-annual variability of monthly MSL and its link to the North Atlantic Oscillation using records from 13 tide gauges located in the German Bight. The amplitudes of the seasonal MSL cycle are not regionally uniform and vary between 20 and 29 cm. Generally, the amplitudes are smaller at the southwestern stations, increasing as one travels to the northeastern part. The amplitudes, as well as the phase of the seasonal cycle, are characterized by a large inter-annual and inter-decadal variability, but no long-term trend could be detected. Nevertheless, in the last two decades annual maximum peaks more frequently occurred in January and February, whereas beforehand an accumulation was detected for the November and December period. These changes in phase in the various sea level time series are consistent with a shift in the annual cycle, which is, however, not significant. The changes are associated with strongly increasing trends in monthly MSL of the winter season (J–M), which are considerably higher compared to the remaining seasons. For the same season, the MSL and North Atlantic Oscillation (NAO) indices show strong similarities, resulting in statistically significant correlations (r ~ 0.7). Hence, these changes are linked with changing pressure conditions over the North Atlantic, which lead to a strong phase of positive values in the NAO index between the 1960’s and 1990’s.
2073-4441
170-195
Dangendorf, Sönke
ba1c5cbe-a385-41dc-8a46-da8cd36cf19d
Wahl, Thomas
6506794a-1f35-4803-b7f7-98702e57e667
Hein, Hartmut
16168733-e23d-482f-be82-ecaa8042f5b0
Jensen, Jürgen
5188f969-c5e8-47e2-9e27-771067712095
Mai, Stephan
d8d86846-a3ca-457f-bfda-b44b8dfe613a
Mudersbach, Christoph
480f1e6e-5496-4a03-b32b-8d321b2350fe
Dangendorf, Sönke
ba1c5cbe-a385-41dc-8a46-da8cd36cf19d
Wahl, Thomas
6506794a-1f35-4803-b7f7-98702e57e667
Hein, Hartmut
16168733-e23d-482f-be82-ecaa8042f5b0
Jensen, Jürgen
5188f969-c5e8-47e2-9e27-771067712095
Mai, Stephan
d8d86846-a3ca-457f-bfda-b44b8dfe613a
Mudersbach, Christoph
480f1e6e-5496-4a03-b32b-8d321b2350fe

Dangendorf, Sönke, Wahl, Thomas, Hein, Hartmut, Jensen, Jürgen, Mai, Stephan and Mudersbach, Christoph (2012) Mean sea level variability and influence of the North Atlantic oscillation on long-term trends in the German Bight. Water, 4 (4), 170-195. (doi:10.3390/w4010170).

Record type: Article

Abstract

Changes in the seasonal cycle of mean sea level (MSL) may affect the heights of storm surges and thereby flood risk in coastal areas. This study investigates the intra- and inter-annual variability of monthly MSL and its link to the North Atlantic Oscillation using records from 13 tide gauges located in the German Bight. The amplitudes of the seasonal MSL cycle are not regionally uniform and vary between 20 and 29 cm. Generally, the amplitudes are smaller at the southwestern stations, increasing as one travels to the northeastern part. The amplitudes, as well as the phase of the seasonal cycle, are characterized by a large inter-annual and inter-decadal variability, but no long-term trend could be detected. Nevertheless, in the last two decades annual maximum peaks more frequently occurred in January and February, whereas beforehand an accumulation was detected for the November and December period. These changes in phase in the various sea level time series are consistent with a shift in the annual cycle, which is, however, not significant. The changes are associated with strongly increasing trends in monthly MSL of the winter season (J–M), which are considerably higher compared to the remaining seasons. For the same season, the MSL and North Atlantic Oscillation (NAO) indices show strong similarities, resulting in statistically significant correlations (r ~ 0.7). Hence, these changes are linked with changing pressure conditions over the North Atlantic, which lead to a strong phase of positive values in the NAO index between the 1960’s and 1990’s.

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Published date: 24 February 2012
Organisations: Energy & Climate Change Group

Identifiers

Local EPrints ID: 393909
URI: http://eprints.soton.ac.uk/id/eprint/393909
ISSN: 2073-4441
PURE UUID: 30e54454-7830-4426-8220-935343fab73b

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Date deposited: 09 May 2016 12:37
Last modified: 04 Nov 2019 19:51

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Contributors

Author: Sönke Dangendorf
Author: Thomas Wahl
Author: Hartmut Hein
Author: Jürgen Jensen
Author: Stephan Mai
Author: Christoph Mudersbach

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