In the weather kitchen, the interaction between the Azores High and the Icelandic Low significantly affects how much warm water the Atlantic carries to the Arctic along the Norwegian coast. However, this rhythm can be disrupted for years.
Experts from the Alfred Wegener Institute finally have an explanation for why: Due to unusual atmospheric pressure conditions over the North Atlantic, low-pressure areas deviate from their normal paths, disrupting the connection between the Azores highs, the Icelandic lows, and the winds. Close to the Norwegian coast. This discovery is an important step towards improving climate models.
Conditions on the Norwegian coast in winter are generally harsh: the wind blows from the southwest for several days or even weeks. Low pressure areas move along the coast, bringing rain and snow with them; The winds they produce determine how much warm water they carry from the southern latitudes of the Atlantic to the Barents Sea and the Arctic. However, this warm water flow may vary.
Climate scientists want to study these fluctuations more closely so computer models can better predict how the extent of Arctic sea ice will change over several decades. Problem: We still don’t fully understand what causes these fluctuations in the complex weather and ocean currents off the coast of Norway and the Barents Sea. However, this is necessary for further development of climate models.
Workaround
A group led by oceanographer Finn Heukamp of the Alfred Wegener Institute and the Helmholtz Center for Polar and Marine Research (AWI) published a study in the journal Communications Earth&Environment in which he and his colleagues examined ocean currents off the coast of Norway. Their focus was on the difference in atmospheric pressure between the Azores High and the Icelandic Low, also known as the North Atlantic Oscillation (NAO), which creates currents off the coast of Norway.
They were particularly interested in the question of why there were (in some cases extreme) deviations from the typical interaction of SAC and weather conditions. Normally the intensity of winds and hence ocean currents is determined mainly by the atmospheric pressure drop across the SAC.
When the SAC is more pronounced, it creates strong air currents that move areas of low pressure northward across the North Atlantic and past Norway. As the atmospheric pressure difference decreases, both winds and low pressure areas lose their strength.
Therefore, the SAC, the trajectory of low-pressure areas and the intensity of ocean currents near the Norwegian coast are often closely related. However, the separation of SAC and ocean currents in the Barents Sea was observed in the late 1990s.
“This unusual split was seen frequently during the winter months between 1995 and 2005,” says Heukamp. “However, the reason for these changes was unclear.” Experts now have an answer, thanks to a mathematical ocean model that simulates the Arctic Ocean at very high resolution.
This phenomenon appears to be caused by an unusual change in the orbit of low pressure areas. Heukamp determined that the flow of low-pressure areas crossing Norway and moving from southwest to north is occasionally interrupted by strong, nearly constant high-pressure areas, also known as high pressures. Second, it pushes fast-moving areas of low pressure out of their normal path. As a result, the SAC and the northern warm water flow are temporarily separated.
Improving climate models
“Currently we still do not know how often such situations occur – for example, whether they occur every few decades – because the observational data we use to compare with our ocean model dates back only 40 years,” – says Heukamp. However, the results obtained are very important in terms of climate modelling.
“Global climate models are simulated on a relatively large scale,” the researcher explains. “With the latest results from our high-resolution analysis of the North Atlantic and Arctic, we have added an important detail that will make Arctic climate modeling even more accurate.” They also show that in the future the SAC, low pressure areas over the Atlantic and ocean currents will increasingly need to be considered together.
The results are also interesting for more accurately predicting the future climate and weather of Central Europe, given that both the transport of warm water and the movement of cold temperatures over the Atlantic affect our mid-latitude weather. Source
Source: Port Altele
