Case 8: the Faroe Islands - Storms

The following is a preliminary assessment of how the Faroe Islands will be affected by climate change - the main hazard in focus in this case is storms. The assessment will be developed further as the fieldwork progress

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Photo: Jógvan Helgi Hansen

Climate conditions

The Faeroe Islands are a North Atlantic archipelago located 320 km north-northwest of Scotland, and about halfway between Norway and Iceland and consist of 18 small islands (Figure 1). The islands have a total area of 1399 km² and extend 113 km from north to south and 75 km from east to west. The islands are hilly, and the highest elevations reaching nearly 890 m above sea level are found in the northern islands (Cappelen & Laursen, 1998).

The climate in the Faroe Islands is greatly influenced by the North Atlantic Ocean, and it is classified as hyper-oceanic (Beil et al., 2015). It is also influenced by the warm Gulf Stream and by the passage of frequent cyclones (NB: the term "cyclone" applies to numerous types of low-pressure areas), which arrive from the south and west depending on the position of the polar frontal zone. Consequently, the climate is humid, unsettled, and windy, with cool summers, mild winters, and small differences between the seasons (Figure 1).

The precipitation pattern reflects the topography of the islands, the precipitation being smallest near the coastal areas and rising to a peak at the center of the hilliest islands. Nearly all coastal areas receive around 1000 mm per year, rising to above 3000 mm in the central parts (Beil et al., 2015; Cappelen & Laursen, 1998; Danish Environmental Protection Agency, 1997).

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Figure 1 Faroe Islands with climate diagram: mean monthly precipitation (shaded bars), mean air temperatures (solid line), and average minimum and maximum temperature (dotted line) at Tórshavn meteorological station for the period 1981–2010. The warmest month is August, with a mean temperature of 11 °C and the coldest is February, with a mean of 4 °C. Accumulated annual precipitation is 1330 mm (Cappelen et al. 2011).

Wind

Being close to the common cyclone tracks in the North Atlantic region the islands have a windy climate. The mean wind speed is generally high in the Faroe Islands, particularly in the autumn and winter. It is normally lowest during summer (4.5-6.0 m/s) and highest during winter (6.5-10.0 m/s). April to August are normally without strong winds, while autumn and winter are particularly windy with numerous gales (Cappelen & Laursen, 1998). A typical year has between 20–40 gale days per winter (Dawson et al., 2010), which usually blow from the west and southwest. The vigorous development of cyclones is typically an autumn and winter phenomenon, sometimes with wind speeds of more than 40 m/s and gusts above 70 m/s. Though the general climate is very windy, calm periods do occur, most often in midsummer, but then only for very short periods.

The air in the lower atmosphere is affected by the hilly islands, causing considerable local winds, as a result of stowing, channeling, and turbulence. This and the fact that the sea currents between the islands are very strong sometimes causes navigational problems for ships. The turbulence in the mountain regions also causes problems for air traffic. Intensive cyclone developments frequently give unstable weather, especially in autumn and winter. Drops in atmospheric pressure of about 20 hPa in 24 hours occur in nearly all months but sometimes the pressure falls more rapidly - occasionally more than 80 hPa in 24 hours - and such situations cause very high wind speeds and considerable damages all over the islands (Cappelen, 2018; Cappelen & Laursen, 1998).

Figure 2 is an example from Mykines (eastern island of the Faroes). The period is August 2018 to January 2021. The winter-summer trend is distinct. The data show 1.3 days/yr with a mean wind speed above 25.5 m/s (i.e. storm) and 29.2 days/yr above 17.2 m/s (i.e. gale). However, this data is the daily mean and as storms often last less than a day, it is interesting to consider the maximum windspeeds (i.e. gust) per day. In the same period, there were 133 and 255 days/yr with gusts above the storm and gale demarcations (i.e. 25.5 and 17.2 m/s), respectively. Thus, 37% and 70% of the days in Mykines had gust at storm or gale level, respectively.

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Figure 2 Wind in Mykines (Eastern Faroe Islands) (data from www.vedrid.fo).

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Photo: Jógvan Helgi Hansen

Hazard and exposure

Historical storminess

A decade ago, Dawson et al. (2010) stated that the literature on changing patterns of North Atlantic winter storminess was generally contradictory. On the one hand, the Intergovernmental Panel on Climate Change (IPCC) in their assessment report four from 2007 in the summary statement refers to a recent increase in mid-latitude storminess, but by contrast, the modeling efforts summarized in the UK Climate Projections 2009 Report anticipate a projected long-term decrease in winter storminess (Lowe et al., 2009 in Dawson et al. 2010), and other studies argued that there is no sign of an enhanced storminess signal associated with recent global warming (Gunther et al., 1998; WASA Group, 1998; Alexandersson et al., 1998; MacClenahan et al., 2001; Barring & von Storch 2004; Alexander et al., 2005; Dawson 2009 – all in Dawson et al. 2010).

In 2013, IPCC wrote in their assessment report five, that studies using reanalyzes continue to support a northward and eastward shift in the Atlantic cyclone activity during the last 60 years with both more frequent and more intense wintertime cyclones in the high-latitude Atlantic (Figure 3). Furthermore, over longer periods studies of severe storms or storminess have been performed for Europe where long-running in situ pressure and wind observations exist. Direct wind speed measurements, however, either have short records or are hampered by inconsistencies due to changing instrumentation and observing practice over time (Hartmann et al., 2013; Krueger et al., 2019).

This also applies to the Faroe Islands (Cappelen, 2021; Cappelen & Laursen, 1998). In most cases, therefore wind speed or storminess proxies are derived from in situ pressure measurements or reanalyzes data of which quality and consistency vary. Nevertheless, it shall be stated that in situ observations indicate no clear trends over the past century or longer, but substantial decadal and longer fluctuations are clear, and with some regional and seasonal trends (Hartmann et al., 2013).

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Figure 3 Geostrophic wind speeds for winter (DJF). Triangles show regions where geostrophic wind speeds have been calculated from in situ surface pressure observations. The ticks of the time (horizontal) axis range from 1875 to 2005, with an interval of 10 years. Disconnections in lines show periods of missing data (Wang et al., 2011. in Hartman et al. 2013)

In 2020, Feser et al. (2020) also found that strong decadal and multidecadal variability concerning high wind speed percentiles and storm frequency, but detected no long-term changes for the last decades. Contrary, Barcikowska et al. (2018) described an observed increase in northern hemispheric storminess towards northern latitudes during the past several decades, which was consistent with the northward shift of storm tracks and their intensity since at least 1970, and that these changes since 1950 at least partly could be attributed to external drivers – mainly global warming. Furthermore, owing to its exposure to the direct impact by cyclones from the North Atlantic, weather extremes in this region frequently cause profound socioeconomic costs. Heavy rainfall and intense winds may cause flooding and storm surges, damaging infrastructure, industry, agriculture, and forestry (Barcikowska et al., 2018).

Hanna et al. (2008) had previously concluded from their analysis of extreme winter values, that storm activity has fluctuated for the last 150 years – also around the Faroe Islands (Figure 4), but they found no sign of an obvious link between storminess and global warming in the past. They also stated that this is in line with conclusions of previous studies investigating North Atlantic cyclonicity and storminess: for example, Alexander et al. (2005) that found a tendency toward more severe, but less, storms in the United Kingdom and Iceland, and Smits et al. (2005) that found no significant trend in storminess over the Netherlands from 1962–2002 (Hanna et al., 2008).

Figure 4 Torshavn (Faroe Islands) annual storminess and trend (“dp(abs)24” is an index – see Hanna et al. 2008: 6748-9)

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In a more recent study, Krueger et al. (2019) found a multidecadal increasing trend in storm activity starting in the mid-1960s and lasting until the 1990s (Figure 5), whose high storminess levels are comparable to those found in the late nineteenth century, which initiated a debate over whether this would already be a sign of climate change. This study confirms that long-term storminess levels have returned to average values in recent years and that the multidecadal increase is part of an extended interdecadal oscillation.

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Figure 5 Standardized time series of annual geostrophic wind speeds averaged over 10 triangles in the northeast Atlantic. The time series of annual percentiles show pronounced interannual and interdecadal variability (Krueger et al. 2019:1923).

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Climate change impacts on storminess

The Danish Environmental Protection Agency stated in 1997 that the Faroe Islands are expected to experience only minor climate changes in the next hundred years, however, at sea, even minor changes can cause dramatic changes in the structure of ecosystems. They at that time expected an increase in the frequency of storms of gale force (Danish Environmental Protection Agency, 1997).

More recent studies conclude that the development of extreme winds related to cyclones under a changing climate in the oceans is an open question (Chang, 2018). The increase from the 1960s to the 1990s and the following atmospheric stilling in northeast Atlantic storminess may have been an early sign of climate change (Barcikowska et al., 2018; Chang, 2018; Hartmann et al., 2013). However, as recent studies highlight, the atmospheric circulation in the midlatitudes is dominated by internal variability (Hanna et al., 2008; Raible et al., 2014), making reliable projections about the future state of the circulation currently infeasible (Krueger et al. 2019:1928).

One study of special interest, concerning storminess in the Faroe Islands, investigated the Euro-Atlantic winter storminess and precipitation extremes under the 1.5⁰C and 2⁰C IPCC warming scenarios. It projected that regions impacted by the strengthening of the midlatitude jet, such as the northwestern coasts of the British Isles, Scandinavia, and the Norwegian Sea, and over the North Atlantic east of Newfoundland, will experience an increase in the mean as well as daily and sub-daily precipitation, wind extremes, and storminess, suggesting an important influence of increasing storm activity in these regions in response to global warming (Barcikowska et al., 2018).

This projected future response indicates also an increase in storm activity towards the northern side of the current storm track, which is between Iceland and the British Isles, so where the Faroe Islands is situated. For the Norwegian Sea, which is just north of the Faroe Islands, the same study found an increase in the frequency of storm occurrences with exceptionally high intensities. The strength of this tendency increases with the intensity of the extreme event, which suggests the possibility of increased frequency of more intense storms. But it is important to note that the authors state that these results should be confirmed by a more elaborate analysis, specifically targeting changes in storms (ibid.).

Photo: Jógvan Helgi Hansen

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Photo: Jógvan Helgi Hansen

The Gulf Stream

The great unknown is how climate change will affect the Gulf Stream. The climate of Central and Northern Europe is highly influenced by the North Atlantic Ocean. Due to ocean heat transport from the tropics northward via the Gulf Stream and its northern extension, the North Atlantic Current (NAC), the north-eastern North Atlantic is exceptionally warm compared with other oceanic regions of the same latitude (Beil et al., 2015). The Gulf Stream System works like a giant conveyor belt, carrying warm surface water from the equator up north, and sending cold, low-salinity deep water back down south. It moves nearly 20 million m3/sec (Caesar et al., 2021). The NAC is mainly forced by the thermohaline circulation, and its fluctuations are supposed to have strongly influenced the climate of the North Atlantic and Northern Europe at various time scales (Beil et al., 2015), and thereby also frequency and intensity of storms and cyclones in the area around the Faroe Islands.

IPCC stated recently, in their Special Report on the Ocean and Cryosphere in a Changing Climate (Collins et al., 2019), that the Atlantic Meridional Overturning Circulation (AMOC) has weakened relative to 1850–1900 (medium confidence), and that it will very likely weaken over the 21st century (high confidence), although a collapse is very unlikely (medium confidence). Nevertheless, a substantial weakening of the AMOC remains a physically plausible scenario (Figure 6). Such a weakening would strongly impact natural and human systems, leading to among others more winter storms in Europe, which will be superimposed on the global warming signal (Collins et al., 2019).

In the latest larger study, Caesar et al. (2021) found that never before in over 1000 years has the AMOC been as weak as in the last decades. They found consistent evidence that its slowdown in the 20th century is unprecedented in the past millennium and linked this to human-caused climate change. They concluded that if we continue to drive global warming, the Gulf Stream System will weaken further – by 34 to 45 % by 2100 according to the latest generation of climate models, which could bring us dangerously close to the tipping point at which the flow becomes unstable (ibid.).

Figure 6 Atlantic Meridional Overturning Circulation (AMOC) changes at 26ºN as simulated by 27 models. The dotted line shows the observation-based estimate at 26ºN and the thick grey/blue/red lines the multi-model ensemble mean. Values of AMOC maximum at 26ºN (in units 106 m3 s–1) are shown in historical simulations (most of the time 1850–2005) followed for 2006–2100 by a) Representative Concentration Pathway (RCP)2.6 simulations and b) RCP8.5 simulations. In c) and d), the time series show the AMOC strength relative to the value during 2006–2015, a period over which observations are available. c) shows historical followed by RCP2.6 simulations and d) shows historical followed by RCP8.5 simulations. The 66% and 100% ranges of all-available CMIP5 simulations are shown in grey for historical, blue for RCP2.6 scenario and red for RCP8.5 scenario (Collins et al., 2019).

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Vulnerability

The Faroe Islands has a population of 51,349 (July 2021 est.) – living on 17 of the 18 islands (CIA, 2021). There are very limited direct statements or descriptions of vulnerability on the Faroe Islands in the literature, but the economy can be used as an indicator of the vulnerability level (Gbetibouo et al., 2010; Hinkel, 2011).

Fishing has been the main source of income for the Faroe Islands since the late 19th century. The fisheries sector accounts for about 97% of exports, and half of GDP (CIA, 2021). But dependence on fishing makes the economy vulnerable to price fluctuations – in other words, high vulnerability of the economy due to low diversification (Gbetibouo et al., 2010). The Faroese economy has experienced a period of significant growth since 2011, due to higher fish prices and increased salmon farming and catches in the pelagic fisheries (CIA, 2021).

The educational level is high, the population living in poverty is low, the GDP per capita is high, and the unemployment is low (CIA, 2021), which all indicate low vulnerability (Gbetibouo et al., 2010). Faroese have a standard of living equal to that of Denmark, and like Greenland, it is an autonomous territory within the Kingdom of Denmark. The annual subsidy from Denmark amounts to about 11% of the Faroese GDP (CIA, 2021). Another proxy to indicate vulnerability is age, which reveals an aging population, which can lead to a high old-age dependency ratio that can slow down the economy on the islands. Further, an aging population might have difficulties handling storms, such as securing housing structures during storms.

According to the Emergency Management Coordinator of the Faroe Islands the Faroese, in general, are less vulnerable to storms, as the housing, buildings, and other infrastructure are constructed to withstand the extreme winds. Emergency calls during storms mainly relate to loose rooftops, but this is rare, as the quality of the houses has improved with the economic development in the recent decades. The terrain is rugged and with many islands the mobility is slow, so assistance from the emergency units can be troublesome. However, search and rescue, or other assistance operations during storms are rare, as people stay inside when storms are announced through media, and the Faroese are in general prepared with supply in their houses to withstand the duration of storms. Tunnels and roads are closed, and ferries and/or aviation are suspended, nationally or regionally during extreme wind events (Emergency Management Coordinator, personal communication 2021).

References

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