Climate and landscapes


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Middalsbreen, an outlet glacier from the 74 km2 ice cap Hardangerjøkulen in southern central Norway, August 30, 2003. Shortly to the right a fresh moraine system is seen, still without vegetation. This is the result of a glacier advance during the 1990's, not caused by lower temperature, but higher winter precipitation. Further to the right another moraine system is seen, the result of another glacier advance during the 1970's, mainly caused by somewhat lower air temperature during the summer.


The relationship of landforms and landscapes to climate is a topic which has simultaneously been regarded as an important focus for geomorphological research, and an approach which has fruitlessly occupied the time of other geomorphologists over the past several decades. The former view has characterised research by many German and French geomorphologists, whereas the latter has prevailed among many Anglo-American researchers. There is little, doubt, however, that a number of processes and landforms associated with fluvial, eolian, glacial and periglacial environments clearly demonstrate that major differences in climate have a profound effect on landscape development. In addition, any landscape is seen to reflect ongoing climatic changes, at least in a number of the minor landforms. By this, any landscape will tend to represent an archive over past and present climatic changes.

Landscapes and geomorphology are, however, not only passive archives of past and present climatic variations. In various ways they interact with climate itself. Geomorphological activity may lead to changes in surface albedo, e.g. by a change in vegetation or by the advance or retreat of glaciers. By volcanic eruptions, greenhouse gasses like water vapour and CO2 is released to the atmosphere. In addition to this, material carried to the sea by rivers, or transported by glaciers or the wind, experiences some degree of chemical decomposition or physical breakdown prior to being eroded and during the subsequent transport. This is the process of weathering, which may influence upon the chemical composition of the atmosphere. Especially the process of carbonation is important in this respect, as it efficiently removes CO2 from the atmosphere. Carbonation plays a particularly important role in the weathering of calcareous rocks.



Generalised temperature diagram based on temperature measurements in the Greenland Ice Sheet (Dahl-Jensen et al. 1998), annotated with a number of historical events around the North Atlantic. MAAT is short for mean annual air temperature. Some of the text in the diagram contains links to additional information.

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Lake Chad

The Sahel region in North Africa. Lake Chad is the dark region near the center of the picture. The area shown covers about 7000 km from west (left) to east. Source: Google Earth.


The Sahara Desert is the most extensive desert on Earth but during the Holocene (the last 12,500 years) it was home to some of the largest freshwater lakes on Earth; of these, palaeolake Megachad was the biggest. The present lake Chad is a minor rest. Landsat TM images and Shuttle Radar Topography Mission (SRTM) digital topographic data reveal numerous shorelines indicating the former outline of the much bigger Lake Megachad (Drake and Bristow 2006). At its peak sometime before 7000 years ago the lake was over 173 m deep with an area of at least 360,000 km2, bigger than the Caspian Sea, which is the biggest lake on Earth today. The morphology of the shorelines indicates two dominant wind systems, one from northeasterly direction, consistent with the present-day winds in the region. The other originated from the southwest. These old coastal features today found in Sahara can be attributed to an enhanced monsoon caused by a precessionally driven increase in Northern Hemisphere insolation at that time, leading to high global temperatures. Subsequent desiccation of the palaeolake is recorded by numerous regressive shorelines in the Sahara Desert.


Lake Chad seen from SSE. The bright pattern visible in the green (vegetation covered) areas are old sand dunes, signalling a previous drier period than now, with dominance of northeasterly winds. The dark blue area is the modern lake Chad, having a surface area of about 1350 km2, comparable to the land area of the Faeroe Islands in the North Atlantic. The maximum water depth is small, only about 11 m. Source Google Earth.


Lake Chad is a shallow lake in northern central Africa, known to vary in size over the centuries. It is economically important for the region, providing water to more than 20 million people living in the four countries which surround it, Chad, Cameroon, Niger and Nigeria. It is located in the western part of Chad, bordering on northeastern Nigeria. The Chari River is the main source of water, providing over 90% of Lake Chad's water, and draining from the mountains farther east in western Sudan. Lake Chad possesses many small islands and mudbanks, and its shorelines are largely composed of marshes. Because it is very shallow (maximum depth c. 11 m) its surface area is very sensitive to small changes in climate, affecting inflow and evaporation. Lake Chad has no clear outlet. It was one of the largest lakes in the world when first surveyed by Europeans in 1823, but it has shrunk considerably since then. An increased demand on the lake's water from the local population has likely accelerated its shrinkage over the past 40 years. The lake presently has an average depth of only 1.5 meters. It apparently nearly dried out in 1908 and again in 1984.

The modern Lake Chad is a remnant of the former inland sea Lake Megachad (Drake and Bristow 2006), which has grown and shrunk in concert with climatic changes during the Holocene (last 12,500 years). At its largest, around 7000 years ago, this lake is estimated to have covered an area of about 360,000 km2.


Old beach ridges (15.55oN, 18.69oE) in southern Sahara, created at the shore of former Lake Megachad. North is up. The wave action (and wind) was from southwest. Today the beach ridges are partly covered by sand dunes moving with the northeasterly winds. The picture measures about 3 km across from west (left) to east. Source: Google Earth.


Inspection of Landsat TM imagery (Drake and Bristow 2006) clearly reveals a wide array of coastal landforms in the Chad Basin including beach ridges, spits, cuspate forelands and deltas that were formed around palaeolake Megachad. The evidence of wave action preserved in the coastal landforms is attributed to a combination of northeasterly and southwesterly winds.

The winds appear to have been seasonal with northeasterly winds in the winter and southwesterly winds due to an enhanced monsoon in the summer. Enhancement of the southwesterly monsoon is important because it contributed to increased rainfall in the Chad basin and to the filling of palaeolake Megachad. Geomorphological evidence from old deltas indicates subsequent drying from the north. Palaeoshorelines have been traced around the lake and found at similar altitudes even when separated by thousands of kilometres. At its maximum extent Lake Megachad was larger than any lake that exists on Earth today. At around 7500-6950 years before now it was 360,000 km2; by 4000 years before now it had shrunk even further and split into three separate lakes, Lake Chad, Lake Fitri and Lake Bodele. As the catchment of Lake Megachad adjoins that of other large lakes to the north it is possible that these lakes provided a humid corridor across the Sahara that would not have existed had the Sahara not been dominated by large closed basins. Such a corridor may have implications for palaeoanthropology and biogeography as the Sahara is thought to provide a barrier to the movement of hominids and animals out of Africa.


Cuspate foreland (15.72oN, 18.75oE) consisting of several systems of beach ridges at the former shore of Megalake Chad, about 500 km NE of the present Lake Chad. North is up. The two main coastlines meeting in the cuspate foreland was controlled by winds from NE and SW, respectively. The picture measures about 15 across from west (left) to east. Source: Google Earth.

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Kilimanjaro glaciers

The stratovolcano Kilimanjaro (5895 m asl.) in northeastern Tanzania (left). The Furtwängler Glacier on the summit plateau of Kilimanjaro (right). The vertical ice cliffs are about 40 m high.


Kilimanjaro (5895 m asl.) is an inactive stratovolcano in northeastern Tanzania, near the border to Kenya . Kilimanjaro is also the tallest free-standing mountain in the world, rising 4,600 m from the surrounding plains. The first official climb of the highest summit was on October 6, 1889 by the German Hans Meyer, the Austrian Ludwig Purtscheller, guided by the Marangu army scout Yohanas Kinyala.

The glaciers on Kilimanjaro have attracted much recent interest, especially in relation to global temperature changes. The Furtwängler Glacier (see illustration above) is located near the summit, and is a remnant of a bigger icecap which once crowned the summit of Mount Kilimanjaro . This glacier is named after Walter Furtwängler, who along with Ziegfried Koenig, were the fourth to ascend to the summit of Kilimanjaro in 1912. Furtwängler Glacier has lost much of its previous volume since first visited by Meyer and Purtscheller in 1889. Between 1912 and the 2000, about 80 percent of the glacier ice on the mountain has disappeared.

A detailed analysis of six ice cores retrieved from the ice fields on the summit of Kilimanjaro shows that those glaciers began forming about 11,700 years ago (Thompson et al. 2002). The ice core records from the Furtwängler Glacier suggests conditions at the Summit of Kilimanjaro today are returning to those characteristic for the site 11,000 years ago.

For decades it has been known that solar radiation and sublimation, not air temperature, are the primary factors for loss of ice from tropical glaciers. In the tropics glaciers exist only at the highest elevations, and their size is controlled more by seasonal changes in precipitation than by air temperatures. Observations of the volume change of glaciers on Kilimanjaro suggest their total volume had already decreased by 66 percent from 1889 to 1953. 

The balance between energy inputs and energy outputs are important to understand 20th century glacier reduction at Kilimanjaro. The primary input of energy is short-wave solar radiation, while ice loss is primarily by way of sublimation, the transition of ice directly to water vapor. Because neither solar radiation and sublimation depends primarily on surface air temperatures, air temperature change does not have a big role in the loss of ice from tropical glaciers. That this also applies to glaciers on Kilimanjaro can be seen from the fact that the ice on Kilimanjaro forms high vertical walls (see illustration above) and finger-like features called penitents (see illustration below), the result of sublimation driven by direct radiation from the sun, rather than ablation caused by warm air.


Examples of ice and snow penitentes from tropical areas. The individual blades are between 1.5 and 2m in height, but may be as high as several meters. Because penitentes are formed by sublimation driven by direct solar radiation, their axis indicate the approximate position of the sun at noon at this latitude and time of the year. Snow penitentes was first described by Darwin (1839). The term penitente date back at least to the beginning of the Little Ice Age, referring to Los Penitentes, the flagellant orders in Spain and Italy.

A prolonged dry period may be responsible for the shrinking glaciers on Kilimanjaro. Kaser et al (2004) found that a marked drop in atmospheric moisture at the end of the 19th century and the ensuing drier climatic conditions are likely to represent the main driver for 20th century glacier retreat on Kilimanjaro. Independent surface observations of water levels from nearby Lake Victoria suggest that water levels have been declining since the end of the 19th century (Thompson et al. 2002), lending support to the notion that the present glacier retreat is caused by more dry conditions, and that the large extent of the glaciers observed by Meyer and Purtscheller in 1889 was the result of a more humid period in eastern Africa at that time, rather than to lower air temperatures.

The ice core from from the Furtwängler Glacier (Thompson et al. 2002) yield evidence of three catastrophic droughts in the tropics 8,300, 5,200 and 4,000 years ago. The ice core also suggest a much wetter environment near Kilimanjaro 9,500 years ago, contemporary with the existence of the large Megalake Chad (see above). The ice core also showed a 500-year period beginning around 8,300 years ago when methane levels in the ice dropped rapidly, suggesting that several lakes of Africa were beginning to dry up. Usually, atmospheric methane levels are assumed to reflect, among other things, the extent of the tropical wetlands.

In addition, the ice core showed an abrupt depletion in oxygen-18 isotopes that may signal a second drought event occurring around 5,200 years ago (Thompson et al. 2002). This coincides with the period when anthropologists believe people in the region began to come together to form cities and social structures. Prior to this, the population of mainly hunters and gatherers had been more scattered. A third marker type in the ice cores is a visible dust layer dating back to about 4,000 years ago (Thompson et al. 2002). This is interpreted as marking a severe 300-year drought which struck the region. Historical records show that a massive drought hit the Egyptian empire at the time and threatened the rule of the Pharaohs. Until this time, people in Africa had been able to exist and thrive in areas that are now just barren Sahara Desert.


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Glacier growth during the last 1100 years on Spitsbergen, Svalbard

Map showing part of the Arctic, with Svalbard in the center.


Within the High Arctic, high climatic sensitivity applies to the Archipelago of Svalbard (77-80oN), located on the boundary between the Norwegian Sea , the Barents Sea and the Arctic Ocean . This was recognized early by Ahlmann (1953) and Lamb (1977). Climatic variations in Svalbard during the 20th century are well documented by meteorological data since 1911 (Førland et al. 1997). For example, a marked warming around 1920 within only 5 years changed the mean annual air temperature (MAAT) at sea level from about –9.5oC to –4.0oC. Later, from 1957 to 1968 MAAT dropped about 4oC, followed by a more gradual increase towards the end of the 20th century (Humlum et al. 2003).

The climatic sensitivity of the Svalbard region presumably derives from various forcing mechanisms. First, Svalbard is located near the confluence of ocean currents and air masses with very different temperature characteristics. The northernmost tip of the North Atlantic Drift presently flows along the west coast of Svalbard , while cold polar water flows south along the eastern coast. Second, the climatic sensitivity is enhanced by rapid variations in the sea-ice extent, which are coupled with both atmospheric and oceanic circulation (Benestad et al. 2002). Finally, Svalbard is located in the major transport pathway of water vapour into the Arctic Basin in association with the North Atlantic cyclone track (Dickson et al. 2000). During the winter season meridional moisture transport along this pathway exhibit a positive relationship with the phase of the North Atlantic oscillation (Jones et al. 2001).


Wahlenbergbreen, central Spitsbergen, July 24, 2000.


Glaciers presently cover about 60 percent of Svalbard (Hagen et al. 1993; Hagen 1996; Hagen et al. 2003). On Spitsbergen , the main island in the Svalbard archipelago (63,000 km2), glaciation is especially extensive in areas near the eastern and the western coast, where many glaciers terminate in the sea. In contrast, glaciers in the central part of the island are smaller, mainly due to low precipitation (Humlum, 2002). The glacier Longyearbreen is located in the relatively dry region of central Spitsbergen , near the main settlement Longyearbyen. At Longyearbyen airport (27 m asl.) the annual precipitation is about 180 mm (w.e.), MAAT is about –5oC and most of Svalbard is situated within the zone of continuous permafrost (Humlum et al. 2003).


Longyearbreen, central Spitsbergen, July 6, 2003, looking south. The site where plants was found below the glacier is indicated by a white spot. The lowermost part of the glacier is covered by debris. The glacier is about 5 km in length.


Longyearbreen (3.2 km2) is about 5 km long and flows from a large cirque at the head of the valley Longyeardalen (Humlum et al. 2005), see photo above. Surging glaciers are frequent on Svalbard (Hagen et al. 1993; Dowdeswell et al. 1991, 1995; Jiskoot et al. 2000), especially in the moist coastal regions (Humlum 2002). There is, however, no evidence for past surge-behaviour of Longyearbreen. Due to the protective debris cover on lower Longyearbreen, a typical feature of many non-surging glaciers in central Spitsbergen , this glacier has not retreated following the 20th century warming around 1920. Instead it has thinned 10-30 m over a considerable proportion of its length, where a protective layer of supraglacial debris is lacking. It is presumably frozen to the bed except for small temperate areas and the maximum surface velocity is low, 1-3 m/yr (Tonning 1996; Etzelmüller et al. 2000).


Ice formations in ice cave below Longyearbreen, May 10, 2002. The section shown is about 1 m high.


Below the equilibrium line crevasses are narrow and few. Perennial supraglacial meandering meltwater channels erode into the glacier surface each summer. When such channels reach a depth of 8-12 m, ice deformation slowly closes the upper part of the channels. Thus, the channels are gradually transformed into englacial, meandering tunnels. A number of these meltwater conduits have now reached the glacier bed 20-50 m below the surface, exposing the glacier-bed interface for considerable distances along their course. During the winter, when water discharge has ceased, these tunnels provide a unique means of access to the glacier bed. In Svalbard glacier deformation is usually low because of low ice temperatures. Therefore, entrances of englacial drainage systems are not completely closed and can be entered during winter using alpine techniques.


Contact between Longyearbreen glacier and slope sediments below, May 10, 2002.


The exposed glacier bed below Longyearbreen generally takes the appearance of a normal talus or scree slope, with no visual indication of glacial erosion. Inspecting the glacier bed in one of the conduits, about 2 km upstream of the present glacier terminus, a well preserved soil layer with in situ vegetation was found at the glacier-bed interface. The vegetation was undisturbed even though presently 30-40 m active glacier ice covers the site. Trimlines above the modern glacier surface indicate that the ice thickness during the Little Ice Age was 20-30 m greater. The lack of evidence for glacial abrasion on boulders and bedrock exposed at the glacier bed led us to conclude that the glacier has remained cold based at this particular place since it overran the site in the past. This is supported by the visual observation of mosses and other plants extending 1-3 cm up in the basal ice without being deformed by the glacial movement. The temperature at the glacier bed was measured to be about -4oC (March-May 2001, 2002, 2003).

Study samples were taken from the subglacial soil at several locations 30-35 m below the modern glacier surface, at 450 m a.s.l. The modern glacier terminus is at 250 m a.s.l., 2 km further downvalley. Macrofossils were investigated in the laboratory, but only few plant species were found. This corresponds well with results from similar investigations of macrofossils from other terrestrial sediments in Svalbard (e.g. Knaap 1989). Salix polaris (polar willow) is the single dominant species, with a high frequency in all our samples. Smaller parts of Gramineae/Juncaceae and moss taxa were also identified. The following moss species were identified: Sanionia uncinata which typically grows on patterned ground in glacier forefields distant from any permanent water sources such as ponds and streams, Tomentypnum nitens which is common in association with relatively high vegetation with moderate winter snow cover, and Distichium spp. and Pogonatum urnigerum that typically live in snow bed communities in topographic depressions. Bryum pseudotriquetrum is common along the margins of relatively large streams in the Arctic region. In addition Myurella julacea, Racomitrium ericoides and Syntrichia ruralis were identified, species that are typical for somewhat drier environments than the other bryophyte species mentioned here. All species found in the subglacial soil below Longyearbreen are known from modern vegetation communities on Svalbard , where they form a widespread element of the present vegetation (e.g. Rønning 1996).


1100 year old vegetation preserved below the glacier Longyearbreen, May 10, 2002. Photo covers about 25 cm across.


Longyearbreen presumably overran the now subglacial soil and vegetation during a winter advance without erosive meltwater activity at the glacier terminus (Humlum et al. 2005). Assuming unchanged prevailing wind conditions, a thick snowdrift probably formed downvalley of the advancing glacier front, just as is the case today along the terminus of Longyearbreen during winter. Such a snow layer may have protected the vegetation to some degree during the glacier advance. It may be speculated that this layer of snow is represented by a white layer of bubbly ice along the glacier-bed interface. Oxygen isotope analysis of ice sampled from this ice layer yielded δ18O values from –11.88 to –12.02, which is only slightly higher than modern winter snowpack values. Modern daily winter air temperatures at the terminus of Longyearbreen typically range from –15 to –30oC.

Frozen samples of soil and vegetation taken from below Longyearbereen were radiocarbon dating (14C). With a probability of 95.4% the period of vegetation growth ended at 1104 cal yr BP. This is a minimum age for the advance of the glacier Longyearbreen over the study site, killing but not destroying the vegetation. Since then the glacier has advanced an additional 2 km downvalley, thereby lowering the altitude of the glacier terminus from about 450 m a.s.l. to 250 m a.s.l. At the time of the advance across the study site the glacier length was about 3 km. The modern length is about 5 km, meaning that the glacier Longyearbreen still is about 2000 m longer than is was about 1100 years ago (Humlum et al. 2005).

The significant net growth of Longyearbreen since about 1100 years ago apparently is consistent with a widespread late Holocene (the present interglacial) climatic development towards cooler conditions in Arctic . This may explain why the ‘Little Ice Age’ (LIA) glacier advance in Svalbard usually represents the Holocene maximum glacier extension and that little evidence for older Holocene ice-marginal morphology is found beyond. From a glaciological point of view, the climatic sensitivity of glaciers in the central arid regions of Spitsbergen would normally be considered small compared to glaciers located in more maritime regions with corresponding higher mass turnover, basal sliding and higher ice flow velocities. Therefore, the about 66 percent length increase from 3 km to now 5 km long Longyearbreen during the last c. 1100 years is quite remarkable, testifying to a climatic development towards conditions more favourable for glaciers at the gateway to the Arctic Ocean during this period (Humlum et al. 2005). This is in concert with the result of direct temperature reconstructions from the Greenland Ice Sheet.

Click here to download a published scientific paper on the above (pdf; 3.2 MB).


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Changing coastal landscapes in Alaska

The location of the settlement Kivalina (ca. 68N, 165W) in northwestern Alaska. Kivalina is located on the northeastern shore of the Bering Strait. Easternmost Siberia is seen to the left. The picture measures about 2500 km from left to right. Source: Google Earth.


Inuits living in the coastal settlement Kivalina in northwestern Alaska (see location map above) are suing 24 oil and gas companies (February 27, 2008), claiming that sea ice melt caused by global warming poses an imminent threat to the Inupiat Eskimos who live there. Kivalina is located at the coast 70 miles north of the Arctic Circle, and have about 390 inhabitants. The complaint says that because of massive sea ice melting, the village is losing its traditional protection from weather and the village must relocate.


Arial photo of Kivalina, showing the partly ice covered Beiring Strait to the left, and land with rivers and lakes to the right. Kivalina is seen to be located on the coastal barrier island, seperated from the mainland by a laguna. The picture measures about 10 km from left to right. North is up. Source: Google Earth.


From a geomorphological point of view, the setting of Kivalina is interesting. The press release say that Kivalina is located on the tip of a barrier reef. This is not the case. The picture above shows the settlement to be located on a coastal barrier island (or shoal), caused by wave action, and thus demonstrating the occurrence of one or several previous periods with extensive open water conditions in the area, extensive enough to generate big waves. If not so, there would have been no barrier island to establish the settlement on. Thus, the present conditions with relatively little sea ice has most likely occurred one or several times before. 

The barrier island on which Kivalina is located must be a relatively new landscape feature, geologically speaking. It is adjusted to the present relative sea level (relative to the land), which in this area probably was reached about 3000-4000 years ago. During this time interval the barrier island have been established by storms during previous open water situations.

Coastal barriers are notorious dynamic landforms, changing form, location and surface relief along with changes in wave activity, wind direction and -strength, and the supply of new sediments (usually sand) by rivers from the hinterland. In periods with high precipitation and high summer river discharge and resulting high sediment transport by rivers, coastal barrier islands tend to aggrade, while the opposite (erosion) dominates in periods with little supply of sediment by nearby rivers. Therefore, not only variations in sea ice, but also a number of other climatic and geomorphological factors control the fate of such delicate coastal features. Usually, coastal barrier islands are considered problematic locations for buildings, roads and other fixed installations. Especially locations near outlets from rivers or lagoons behind are exposed to rapid changes in the coastal outline.

In the Arctic mosquitoes represent a major nuisance, especially in July. Presumably the location for Kivalina was chosen to avoid mosquitoes from the many lakes in the hinterland, and to be close to the open sea during the open water period (summer). The number and outline of the numerous lakes in the hinterland are signalling the existence of permafrost in the area. Barrier islands tend to orient themselves perpendicular to the dominant wind direction during the open water period (summer). In the present case the prevailing summer wind direction apparently is from southwest, helping to keep the mosquitoes at bay in the hinterland, away from Kivalina.


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Formation of the Zuiderzee in the Netherlands

Map showing the outline of the Netherlands with the developing Zuiderzee around year 100 (left) and around year 1000 (centre), according to Tramplers Geographischer Mittelschulatlas, 8th Ed., Wien. The map to the right shows the distribution of land sea 1658 according to Janssonius Map of the Republic of the Seven United Netherlands.


The storm Grote Mandrenke (Great Drowning of Men) strikes the Netherlands in January 1362. Hurricane-force winds with enormous waves and a considerable sea level rise (a storm surge) due to the combined action of push by the wind and lifting of the sea surface because of low air pressure flooded extensive areas of the Netherlands, killing at least 25,000 inhabitants. This number shoulf of cause be seen in relation to the much smaller population at that time than now. The storm also flooded and eroded large land areas in western Slesvig, Denmark, whereby sixty parishes is said to have disappeared totally. Also southern England was severely hit by the storm, with much damage on buildings and infrastructure.

The 1362 storm resulted in severe coastal erosion, contributing to the opening of a pre-existing topographical low in the Netherlands towards the North Sea. This process was already initiated by previous storms, and after a disastrous flood in 14 December 1287 (St. Lucia's flood) the name Zuiderzee came into general usage for this 120 km long pocket-like extension of the North Sea. The 1287 flood is the fifth largest flood in recorded history, and is believed to have drowned somewhere between 50,000 and 80, 000 people. 

The North Sea itself is also, in geological terms, a new feature in Europe. Following the termination of the last ice age about 12,500 years ago, the present North Sea was dry land. But due to the general (eustatic) sea level rise which followed until about 5000 years ago because of the melting of the last remnants of the big ice sheets in Europe and North America, and the reduction of the ice sheets in Greenland and Antarctic, global sea level rose and the North Sea was flooded. Before the North Sea expanded to its present size, a shallow topographical depression existed where the Zuiderzee later formed. Of cause this area had poor drainage, and over time became partly filled with peat. During storms like the Grote Mandrenke this peat was easily eroded, and the North Sea extended rapidly inland to form the Zuiderzee.

Around the Zuiderzee many fishing villages grew up and several of these developed into fortified towns with important trade connections with other ports in the Baltic Sea and in England. The village Amsterdam at the southern end of Zuiderzee was one of these settlements which later developed into a major city. Later this trade with base in the Zuiderzee developed with connections to most of the world. The associated economy formed the basis for Netherlands later period of status and glory, and the trade activities were also foundation for establishing its colonial empire.


Zuiderzee (IJsselmeer) as seen from north (left), and from the southeast (right). The big dam Afsluitdijk can be seen in the centre of the picture to the left. Between this dike and the open North Sea, a complex systems of tidal channels are seen. The distance from the barrier island coastline in the foreground to the innermost part of IJsselmeer is about 120 km. Reclaimed areas, polders, are seen in the foreground of the picture to the right. The city Amsterdam is located at the southern tip of IJsselmeer (the former Zuiderzee). Source: Google Earth.


It was a severe storm with new floodings in 1916 that prompted the early 20th century construction a large enclosing dam to reclaim parts of the Zuiderzee. The construction of this dam, the Afsluitdijk, for the first time made it possible to control changes of water level in the Zuiderzee during storms. With the completion of the dam in 1932 the Zuiderzee became the inland sea Ijsselmeer, and large water covered areas could be reclaimed for farming and housing by construction of surrounding dikes and pumping. These newly reclaimed areas are today known as polders.


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