Morphodynamics of Recherchefjorden Accumulative Coasts Since the End of the Little Ice Age

The Arctic Ocean, and thus the Svalbard Archipelago, has undergone rapid climate changes over the past few centuries (IPCC 2021). The climatic conditions prevailing during the Little Ice Age (LIA) resulted in an increase in the area of glacial systems (Martín-Moreno, Allende-Álvarez 2016, Zagórski et al. 2023). Following end of the LIA, there was a gradual warming of the climate since the beginning of the 20th century, particularly in the early 21st century (Christiansen, Ljungqvist 2012). Since the end of LIA, there has been a progressive recession of glacial systems, and episodes of surges have appeared with varying intensities (Zagórski et al. 2023). The consequences of such changes have been alterations in the polar environment, including melting glaciers, melting permafrost and changes in the extent of sea ice. These changes also directly affect the coastline of Svalbard. As the glacier surfaces decrease, the deglaciated areas, including coastal zones, are being exposed to the interacting marine and land processes, in these so-called paraglacial coasts (Ballantyne 2002, Forbes, Syvitski 1994, Slaymaker 2011).

The last 20 years of research have shown that Svalbard shoreline to have undergone significant changes due to a combination of factors such us intensified delivery of glaciofluvial sediments, erosion of cliffs and beaches by storm waves and exposure of new shores by retreating glaciers (e.g. Bourriquen et al. 2018, Kavan 2019, Kavan, Strzelecki 2023, Mercier, Laffly 2005, Strzelecki et al. 2017, 2018, 2020, Zagórski et al. 2012). These changes have also resulted in the accumulation of coastal forms, such as spits, bars and tombolos, which are the landforms developed by the deposition of sediment along a coastline.

Accumulation coasts (spits, barriers and beaches with storm ridges) occur, among others, in the Recherchefjorden (Recherche Fjord) region (Harasimiuk 1987, Harasimiuk, Jezierski 1991, Jarosz et al. 2022, Zagórski 2011, Zagórski et al. 2012, 2013). In Harasimiuk and Jezierski’s 1991 study, the accumulative coasts in Recherchefjorden were classified as beaches with fully developed profiles, sand bars, tidal flats, or deltas. Recently, a more detailed and comprehensive classification of paraglacial coasts has been developed for this region, which can undoubtedly be considered universal for all polar coasts (Jarosz et al. 2022). In this paper, the fjord coasts were classified based on four criteria: coastal material, genesis and origin, morphological and morphodynamic. The accumulative coasts were classified into three groups:

Delta/estuary composed of glaciogenic or fluvial gravel;

Despite the increasing number of studies on paraglacial coasts, many issues require more detailed research. There are frequent works presenting quantitative changes in the range of coastal areas (e.g. Bourriquen et al. 2018, Kavan 2019, Zagórski et al. 2020), or qualitative ones describing paraglacial coasts and their types (e.g. Harasiumiu, Jezierski 1991, Jarosz et al. 2022), but there is no work focussing on the evolution of accumulation forms that emerged after the LIA. This paper describes the rate of development and factors that allow the formation and development of paraglacial accumulation forms such as spits. In addition, based on the directions of growth of accumulation forms, the system of coastal currents on the Recherchefjorden was reconstructed.

Recherchefjorden is located in the north-western part of Wedel Jarlsberg Land in western Spitsbergen, the largest island in the Svalbard Archipelago, and flows into Bellsund (Fig. 1). The fjord is approximately 7 km long, 4–5 km wide and covers an area of 34 km² (Moskalik et al. 2018). It has a north–south orientation. The relatively small area and the large diversity of coasts make Recherchefjorden an excellent site for observing processes occurring throughout the Svalbard Archipelago, and in a broader perspective, also in the High Arctic. The shores of the fjord are diverse in terms of their origin and material (Jarosz et al. 2022). The fjord is located within several geological formations, which results in a high diversity of lithology in the area (Birkenmajer 2004, NPI 2016).

Fig 1.

The shores of Recherchefjorden are an example of paraglacial coasts significantly shaped by marine processes, including wind and oceanic swells as well as longshore currents. Due to its sheltered location, the interior of the fjord beyond the Lægerneset-Reinodden section (the north-western part of the fjord) is shaped by low-energy waves (Zagórski et al. 2013). In the Bellsund area, dominant winds come from the ENE, WNW and S directions, which is conditioned by the terrain’s orography (Mędrek et al. 2014, Zagórski et al. 2013, 2019). The wind wave height reaches up to 1.1 m (Majewski et al. 2016). A particular case is waves generated by storms, which occur increasingly often along the western coast of Spitsbergen. Although most of them occur in winter, those occurring in spring and autumn are the strongest (Wojtysiak et al. 2018). Storms waves strongly affect the coastal zone (abrasion), especially when shore ice forms in late winter (Rodzik, Zagórski 2009, Zagórski et al. 2015).

For the study, sections of the coast grouped in several areas were selected (Fig. 1):

Area 1 – the north-western coast of the fjord – a spit closing Josephbukta (Joseph Bay). The area is located in the marginal zone of Renardbreen. The spit began to form in the 1930s/1940s as the glacier retreated from the Josephbukta area. It is currently about 900 m long, with its southern expanded part, which is the subject of this study, measuring 250 m. The spit is adjacent to the frontal moraines of Renardbreen from the north and to the tidal flat formed by the fluvioglacial waters of Renardbreen from the northwest.

The source data used for the reconstruction of the development of paraglacial accumulation forms can be divided into the following categories (Table 1):

Field geomorphological mapping of land areas,

The analysis and determination of the coastline extent for individual research areas were carried out in accordance with the methodology presented in the studies of Zagórski (2011), Zagórski et al. (2020) and Jarosz et al. (2022). The main measured element was the position of the storm ridge formed during high-water levels. A precise representation of the coastline was obtained through photogrammetric imagery (UAV - Unmanned Aerial Vehicle DJI Phantom 4). Absolute calibration was achieved using ground control points, whose accurate positions were determined using Global Navigation Satellite System (GNSS) receivers (Leica System 500 SR 530 and Topcon Hiper HR), relative to the reference station (CALYpoint) (Zagórski 2011). The data processing (DEM - Digital Elevation Model, orthophotomap) was conducted using Agisoft Metashape Professional v. 2.0.1. Changes in the accumulative coasts were determined based on the analysis of aerial photographs in GlobalMapper v23.0_PL. The WGS84 – UTM33 coordinate system was used. A comparison of photographs for individual areas allowed for the determination of the axis of the spit for Areas 1, 3, 4, 5, 6, 7 and 8. In other cases, changes were minimal (Area 2) or the form had developed before the analysed period (Area 9). After determining the axis of the spit, the length of the form along the axis was measured. The change in the length of the form over a specific time interval was divided by the number of years in the period, resulting in an annual growth rate of the form m·a⁻¹ (meters per annum). Considering the direction of spit development, the dominant direction of longshore currents can be clearly defined. This made it possible to reconstruct the directions of material transport in the fjord.

The interior of the fjord is influenced by weakened and dispersed swells that come from the open sea (Herman et al. 2019, Wojtysiak et al. 2018). Under favourable conditions, the waves can reach the tidal flat in Vestervågen, especially during the occurrence of spring tides (Fig. 13). From the open sea, the waves entering from the west undergo refraction in the area of Pocockodden and then Rollestonpynten before penetrating into the fjord (Zagórski et al. 2019). These conditions were observed in satellite images from 2013 and 2018 (e.g. Figs 2F, I, 4E, F and 5E, F). On Area 1, the material is transported along the spit and deposited at its end. Waves approaching from the NE broke at the end of the spit, and changed direction to the west along its edge. The more frequent occurrence of such waves may have contributed to the formation of the spit headland in the NW part of the spit (Fig. 2I). A similar impact of waves from the NE was recorded in the satellite images from 2013 and 2018 in Areas 2 and 4 (Figs 4E, F and 6F, H).

Fig 13.

The formation of the system of accumulation forms (spits, beaches with a developed profile) is mainly influenced by the system of longshore currents. They cause the transformation of the already existing coasts and the transport of material (longshore drift) and its accumulation in some sections (Zagórski et al. 2013, 2019). Conditions favouring the above-mentioned phenomena are shown in Figure 13. They occur episodically or periodically, independently of the general circulation of water in the fjord or the phenomena of tidal currents. During the increased supply of material with a favourable wave pattern, tides and longshore current, subsequent stages of spits development are created. This can be seen in the formation of storm ridges, the next generation of which are clearly visible, for example, in Areas 1, 5, 8 and 9. Also during favourable conditions, more spits develop, as is the case in Areas 3, 6 and 7. Therefore, the conclusion is that the accumulation forms currently observed in the fjord develop ‘in leaps’, i.e. in conditions of intensive supply of material, which guarantees their stabilisation and the possibility of long-term survival.

There is a whole system of longshore currents in Recherchfjorden (Fig. 13). The western coast of the Recherchefjorden is shaped by the longshore current flowing from the north (Harasimiuk, Jezierski 1987, 1991, Jarosz et al. 2022, Zagórski 2002, 2011). This is evidenced by the elongation of Josephbukta (Area 1) and the development of spits on the west coast between Rollestonpynten-Tomtodden-Vestervågen (Areas 2 and 3). Along the shores of the island of Reinholmen (Area 5), the longshore currents flow south. Along Rubypynten (Area 6), a local material transport system has developed from the east to northwest, and after crossing the northernmost point of the cape, the current turns south and flows towards the Chamberlinelva estuary (Area 4). Another longshore current flows from the east along the eastern outwash plane, causing the development of spits at the mouth of the Recherche Lagoon (Area 7). The east coast of the Recherchefjorden (Areas 8 and 9) has been shaped mainly by wave action and the transport of material by longshore drift flowing south.

With climate fluctuations, the conditions prevailing in the coastal zone change (Mędrek et al. 2014, IPCC 2019, 2021, Zagórski et al. 2019). One of the factors directly affecting Arctic coasts is the state of sea ice. In recent years, a significant shortening of the ice cover period has been observed inside fjords and along the coast (Urbański, Litwicka 2022). Consequently, this has led to the prolongation of the period of shore shaping by waves, especially storm waves, which often occur in winter, thus increasing the dynamics of coastal processes (Barnhart et al. 2014). Along with the increasingly shorter ice cover period in this part of the fjord, the coast is deprived of protective ice cover (Rodzik, Zagórski 2009, Zagórski et al. 2019). This is particularly evident in Area 5, where the development of a spit in the southwestern part of Reinholmen began with the increasingly shorter ice cover period in Vestervågen since the 1990s.

Due to climate change, the coasts of Recherchefjorden have undergone increasingly significant transformations in recent years. The phenomena and processes occurring in the Recherchefjorden are typical of other areas in the High Arctic.

The end of the 20th century, and especially the 21st century, were characterised by an increasing pace of development of accumulative forms in the distinct internal parts of Recherchefjorden. The process itself was episodic (periodic) in nature. Under favourable conditions, there was an intensification of material transport processes and the construction of forms, which over time became stable forms.

Contemporary changes in the morphology of accumulation forms depend on the intensity of marine processes. In the case of Recherchefjorden, the greatest impact is from wave action (wind and swell), which penetrates deeply into the interior of the fjord, as well as longshore currents. More frequent winds from the W, NE and NW sectors lead to the expansion of spits in a southerly direction. Additionally, the fact that the period of fjord ice coverage is getting shorter leads to an increase in the intensity of coastal processes.

Considering the development of accumulative forms along the Recherchefjorden coast, it is possible to reconstruct the dominant patterns of longshore currents that determine the direction of material transport. The western coast is influenced by a southward-flowing longshore current, as are the Reinholmen coasts. The area from the Chamberlinelva river mouth to Rubypynten and the Recherchebreen eastern outwash plain are influenced by a westward-flowing longshore current. Meanwhile, along the eastern coast of the fjord, patterns of southward-directed coastal longshore currents dominate.