User:Timothy2b/sandbox Hypothetical Danish Mountains

Premise
Exploration of what the climate of Northern Europe could look like if a mighty mountain range had existed along Denmark's Jutland peninsula, stretching south into northern Germany. Some smaller mountains would probably exist on the islands of the Danish Archipelago as well.

In Denmark, this would, as is rather self-explanatory, give the country mountain regions which it currently lacks, rendering a cold, alpine climate in said locations. Most of the country, lying east of the mountains, would be sheltered from the prevailing westerly winds, meaning the Atlantic dominance of the climate would dwindle. While some marine moderation would still be expected from the surrounding bodies of water, low-pressure systems moving in from the North Sea would have far less of an effect on the climate. This would likely cause much colder and snowier winters, with temperatures instead staying below freezing for the most part. Still, due to the relatively narrow mountains and an overall westerly air flow, winter temperatures would still be expected to be far milder than areas on similar latitudes in Canada and Russia. Winters would instead be expected to be similar to modern northern Svealand in Sweden. A snow cover for most or all of the winter could be expected, with the extent of sea ice being largely dependent on weather conditions, but expected in the narrower straits. Summer temperatures would likely increase by a few degrees, as the mountains would block cool low-pressure systems, giving way to warm high-pressure systems to move in from Eastern Europe. While not affected to quite the same degree as winters, summers would still become warmer. The exception to these changes would be the west coast of Jutland, where the mountains would instead cause orographic lift and thus increase precipitation, similar to what happens on the Norwegian west coast. This would likely mean similar winters to today, though far wetter, while summers could get somewhat cooler due to increased precipitation.

In Sweden, the effects of these mountains would be most evident of the southern third of the country, as, similar to Denmark, they would largely block the incoming low-pressure systems from the Atlantic. This means that winter temperatures would probably become more similar across the country, though still markedly colder in the North. All of Svealand, including the capital of Stockholm, as well as most of Götaland could be expected to have a permanent snow cover throughout the winter, as the alternating dominance of mild, Atlantic air and cold, continental air would be replaced by a continuous presence of the latter. Sea ice would also become far more widespread in the Baltic, with the remainder of the Gulf of Bothnia south of the Bothnian Bay freezing over completely. While the rest of the Baltic south of Åland would likely not freeze over every year, reliable ice cover would likely occur along the Swedish east coast, with intermittent ice accretion elsewhere. The large lakes of southern Sweden, including Mälaren, Vättern, och almost all of Vänern, would freeze over in winter. Like Denmark, summer temperatures would increase, though at a gradient, with the South seeing similar increases to Denmark while northern Götaland and Svealand only see marginal increases. Also like Denmark, one exception would likely be seen in Sweden, with the northern west coast not being as affected by the mountains as it is not shielded from the mild winds to the same degree as the South. This would render the unusual result of the southern part of the west coast being colder in winter than the north. Thus, it would likely be the only part of Sweden to not have a reliable winter snow cover. Still, the increased influence of continental airflows would likely make the area colder than it is today, yielding incessant freeze-thaw cycles in winter. Summer temperatures would remain relatively unchanged, increasing only marginally.

In Germany, the mountains would run down Schleswig-Holstein into eastern Niedersachsen, extending south to Hannover. This would create a large climactic divide between the west and east sides of the mountains. Cities like Hamburg, on their western side, would feature largely unchanged temperatures but increased precipitation due to orographic lift, while the eastern side would get colder, snowier winters and warmer summers, though still not rivalling the cities of the Upper Rhine Valley.

In the Baltic Sea, sea ice cover would increase significantly, with the waters of the Archipelago Sea by Åland and northwards completely freezing over in wintertime. The Gulf of Finland would also freeze, potentially allowing crossings between Finland and Estonia, as would the waters of the Estonian coast and the Bay of Riga. The Curonian and Vistula Lagoons would also freeze up entirely. Ice cover would be expected all along the Swedish east coast, including along Öland and Gotland. Ice along the Lithuanian and Polish coasts would likely be frequent but subject to variation depending on wind direction. Sea ice in northeast Germany and the Danish straits would be largely present in narrower straits, but its thickness and spread would likely depend on the severity of the winter. The same can be said for the remaining open waters of the Baltic, where ice cover would be intermittent and quite variable.