Sea level
Last updated 23 September 2022
Should a single quantity need to be applied to describe the climate on the Earth, it would probably have to be the global sea level. The global sea level reflects both short- and long-term changes in the climate of the atmosphere, the cryosphere, the land areas, and the oceans. In Svalbard, the sea level is monitored in Barentsburg. For comparison, sea level measurements for Tromsø and Vardø are also presented.
What is being monitored?
Sea level
The figure shows the annual average sea level in Barentsburg. The strong decline in the observed level is thought to reflect a weakening of the West Spitsbergen Current. Other factors may also have contributed. For instance, land uplift after the last Ice Age is greater in the Arctic than in other areas and this helps to give less sea-level rise in the Arctic than elsewhere in the world. There are no data for 2019, 2020 and 2021.
(Cite these data: Norwegian Polar Institute (2022). Sea level in Barentsburg – annual mean. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: https://mosj.no/en/climate/ocean/sea-level.html)
The figure shows the annual average sea level in Tromsø. Whereas a decline is observed in the first part of the monitoring period (1948-1985), the sea level has generally risen in the second part (1985-2021). In the last two decades sea level in Tromsø has slightly positive trend of 0.4 mm/yr.
(Cite these data: Norwegian Polar Institute (2022). Sea level in Tromsø – annual mean. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: https://mosj.no/en/climate/ocean/sea-level.html)
The figure shows the annual average sea level in Vardø. Whereas a decline is observed in the first part of the monitoring period (1948-1985), the sea level has generally risen in the second part (1985-2021). In the last two decades sea level in Vardø has very slight postive trend (0.06 mm/yr).
(Cite these data: Norwegian Polar Institute (2022). Sea level in Vardø – annual mean. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: https://mosj.no/en/climate/ocean/sea-level.html)
Details on these data
| Last updated | 23 September 2022 |
| Update interval | Yearly |
| Next update | March 2024 |
| Commissioning organization | Norwegian Polar Institute |
| Executive organization | Norwegian Polar Institute |
| Contact persons | Tore Hattermann |
Method
Calculations of monthly and annual mean sea levels based on average hourly heights.
All these data show only relative sea-level changes, because they can include movement of the land on which the tide gauge is situated. In particular, land movements are caused by isostatic adjustment resulting from the response of the mantle to the melting of large ice sheets. The rate of land uplift for northern Norway is several millimetres per year on a time scale of more than one decade.
Revised Local Reference (RLR) data are used from the Permanent Service for Mean Sea Level (PSMSL) data set. In order to construct time series of sea-level measurements at each station, the monthly and annual means have to be reduced to a common datum. This reduction is performed by the PSMSL making use of the tide gauge datum history. The PSMSL recommends that only RLR data should be used for time-series analysis (see Revised Local Reference (RLR) Definition on the PSMSL web page).
Quality
It is necessary to make periodic geodetic surveys to determine any vertical changes of the benchmark at the tide gauge station.
Other metadata
The Murmansk Administration for Hydrometeorology and Environmental Monitoring Environment, Arctic and Antarctic Research Institute and the Permanent Service for Mean Sea Level also have these records.
Status and trend
Sea level measurements from Tromsø, Vardø and Barentsburg all have the same properties, and high correlation between the annual mean change in sea level at these stations implies that long-term variability in these regions is shaped under the influence of the same driving forces.
All three time series (Barentsburg, Tromsø and Vardø) show negative trends throughout the period. Barentsburg in 1949–2018 (no data for 2019) has the maximum negative trend in annual sea level variability (-2.7 mm/yr). This trend is negative for all months, and maximum values for the trend are in June and October. The winter months contribute least to the trend. Tromsø and Vardø have a negative trend of –0.49 mm/yr and -0.26 mm/yr throughout the measurement periods correspondingly.
Tromsø and Vardø show a different variability in the period prior to than after 1985. Before 1985, there is a stable, significant negative trend for Tromsø (-2.7 mm/yr) and for Vardø (-2.35 mm/yr). The maximum negative values in the trend in this period were achieved in October and December for Tromsø, and in January and September for Vardø. The linear trend in the inter-annual variation for the period after 1985 is slightly negative in Tromsø (-0.07 mm/yr) and positive in Vardø (0.8 mm/yr). In Tromsø there are six months (January, February, March, July, August and October) with negative values and six months (April, May, June, September, November and December) with positive values, whereas in Vardø there are only three months (January, February and October) with negative values.
Causal factors
The global sea level will rise due to climate change. This takes place because large masses of ice on land melt and water expands when it is heated. In addition, the sea level is influenced by large-scale variations in ocean currents and dominant wind and pressure conditions.
The most significant contribution to the rate of global sea level rise has so far been increasing sea temperatures, decreasing salinity and a reduction in pressure at sea level. Rising temperatures and reduced salinity affect the density in the water, thus raising the sea level without there being more water in the seas for that reason.
As the land in Svalbard and North Norway is still rising after the last Ice Age, a global rise in sea level does not have the same effect on measurements of the relative sea level. In Svalbard, melting of glaciers also affects the land uplift, because the land rises more when the weight of the glaciers is reduced when they melt.
Consequences
A rise in sea level may threaten infrastructure and cultural heritage remains in the shore zone in Svalbard. Increased erosion affects the coastline, and there are many cultural heritage remains on the coast.
About the monitoring
The global sea level has risen by about 120 metres since the last Ice Age, some 20,000 years ago, mostly due to melting of the huge Ice Age ice caps.
Despite this large rise in the global sea level, most of the Norwegian coast has experienced a drop in sea level. This is because Norway and the rest of Scandinavia have undergone substantial land uplift due to the vast Scandinavian ice sheet having melted away, its weight thereby disappearing.
Whereas melting of ice and expansion of water result in a rise in sea level in the longer term, variations in ocean currents, winds and changes in pressure give sea-level changes that can be observed over shorter time periods. Sea-level changes in time and space, together with other climate parameters, may therefore help to explain how climate changes occur in the sea.
Places and areas
- Barentsburg
- Tromsø (Norwegian mainland)
- Vardø (Norwegian mainland)
Relations to other monitoring
Monitoring programme
- None
International environmental agreements
- None
Voluntary international cooperation
Related monitoring
- None
Further reading
Links
- The Permanent Service for Mean Sea Level (PSMSL) has been responsible for the collection, publication, analysis and interpretation of sea-level data from the global network of tide gauges.
- Murmansk Administration for Hydrometeorology and Environmental Monitoring environment has been responsible for observations of the sea level at the Barentsburg tide gauge station.
