Arctic Sea Ice Changes and its Relation with Storm Ridge Occurrence and Active Layer Changes in the Fyrsjöen Lake catchment on the West Coast of Svalbard
By:
Mohammad Hassan Khajeh Abdollahi, Jonas Akerman
Sea ice is declining in the Arctic Basin and has several impacts on the costal waters of Svalbard. This study focus on the Fyrsjöen Lake catchment on the west coast of the main Island of Svalbard, Spitsbergen. In “normal years” sea ice formed during the winter is protecting the shores of the west coast of Spitsbergen and wave action is insignificant. Global climate changes and the following sea ice reduction have resulted in a higher frequency or longer time of ice-free area on the west coast of Spitsbergen during autumn and winter. Consequently there is a ice free area between the sea ice and the coast during a considerable part of the winter. This area and the fetch distance is long enough to allow high storm waves to form during westerly storms. The waves build stable and durable storm ridges by coarse sand and beach cobbles along the coast. These ridges are frequently built across the outlets of costal river catchments, which drain into the Arctic Ocean. The ridges that contain a high amount of seaweeds freeze very hard during the winter and become as strong as concrete. In the following summer, ice and snow in the catchment begins to melt and flow toward outlet, which then is blocked by the storm ridge. The result is that the water is trapped and cannot flow out freely. Water levels rise within the catchment and flooding occur at all low levels. The flood influence all low lying bog areas and also damages the breeding ground for birds and also makes the active layer deeper. In mid July the ridges finally break trough thermokarst processes. A flush flow will drain the Fyrsjöen Lake catchment during a few days with a discharge of up to 6 m3/s while its normal maximum discharge is about 0.3 m3/s. This huge discharge also causes a lot of river bed erosion which lower the outflow threshold.
The study investigates the storm ridge formation and the active layer changes relation to Arctic sea ice distribution changes. It was concluded that storm ridge occurrence is inversely correlated with Arctic sea ice extent and Arctic sea ice area. It means that the observed sea ice reduction clearly increases the probability of storm ridge occurrence. There is a critical span in sea ice extent between 12 to 12.2 million km2. By decreasing sea ice extent from 12.2 to 12 million km2 the probability of storm ridge occurrence raises sharply. It was concluded that storm ridge occurrence is correlated with the number of events with westerly winds more than 7 m/s, during autumn and winter in the area. The reduction of the Arctic sea ice has clearly indirect correlations with an increase in the depth of active layer within the catchment area.
The general result of the study indicate that the reduction of Arctic sea ice increases the probability of storm ridge occurrence and as a result of flooding in the catchment there is an increase in the depth of active layer as well as ecological disturbances.
By:
Mohammad Hassan Khajeh Abdollahi, Jonas Akerman
Sea ice is declining in the Arctic Basin and has several impacts on the costal waters of Svalbard. This study focus on the Fyrsjöen Lake catchment on the west coast of the main Island of Svalbard, Spitsbergen. In “normal years” sea ice formed during the winter is protecting the shores of the west coast of Spitsbergen and wave action is insignificant. Global climate changes and the following sea ice reduction have resulted in a higher frequency or longer time of ice-free area on the west coast of Spitsbergen during autumn and winter. Consequently there is a ice free area between the sea ice and the coast during a considerable part of the winter. This area and the fetch distance is long enough to allow high storm waves to form during westerly storms. The waves build stable and durable storm ridges by coarse sand and beach cobbles along the coast. These ridges are frequently built across the outlets of costal river catchments, which drain into the Arctic Ocean. The ridges that contain a high amount of seaweeds freeze very hard during the winter and become as strong as concrete. In the following summer, ice and snow in the catchment begins to melt and flow toward outlet, which then is blocked by the storm ridge. The result is that the water is trapped and cannot flow out freely. Water levels rise within the catchment and flooding occur at all low levels. The flood influence all low lying bog areas and also damages the breeding ground for birds and also makes the active layer deeper. In mid July the ridges finally break trough thermokarst processes. A flush flow will drain the Fyrsjöen Lake catchment during a few days with a discharge of up to 6 m3/s while its normal maximum discharge is about 0.3 m3/s. This huge discharge also causes a lot of river bed erosion which lower the outflow threshold.
The study investigates the storm ridge formation and the active layer changes relation to Arctic sea ice distribution changes. It was concluded that storm ridge occurrence is inversely correlated with Arctic sea ice extent and Arctic sea ice area. It means that the observed sea ice reduction clearly increases the probability of storm ridge occurrence. There is a critical span in sea ice extent between 12 to 12.2 million km2. By decreasing sea ice extent from 12.2 to 12 million km2 the probability of storm ridge occurrence raises sharply. It was concluded that storm ridge occurrence is correlated with the number of events with westerly winds more than 7 m/s, during autumn and winter in the area. The reduction of the Arctic sea ice has clearly indirect correlations with an increase in the depth of active layer within the catchment area.
The general result of the study indicate that the reduction of Arctic sea ice increases the probability of storm ridge occurrence and as a result of flooding in the catchment there is an increase in the depth of active layer as well as ecological disturbances.
هیچ نظری موجود نیست:
ارسال یک نظر