Higher waves further jeopardize the Arctic

21 April 2016, by CEN Universität Hamburg

Photo:

Characteristic pattern: wave-fractured Arctic sea ice.

By the end of this century, the Arctic could experience up to seven ice-free months per annum if greenhouse gas emissions are not reduced. Increasingly ice-free waters will trigger novel and higher waves.

By the end of this century, the Arctic could experience up to seven ice-free months per annum if greenhouse gas emissions are not reduced. Increasingly ice-free waters will trigger novel and higher waves. Oceanographer Mikhail Dobrynin from Universität Hamburg’s Center for Earth System Research and Sustainability (CEN) made this prediction today during the General Assembly of the European Geosciences Union (EGU) in Vienna, Austria. More powerful waves will break up the sea ice faster and affect pristine seabed and coastal areas.

The Arctic sea ice edge forms a natural barrier that slows down waves. The lower the total sea ice extent gets, the more space is available for growing wave activity. As the Arctic sea ice cover is dwindling in the course of global warming, winds take up speed. According to Mikhail Dobrynin’s research results, this produces waves in larger numbers and sizes. If such waves hit an ice edge, they will crack it up further and make the ice melt faster (see figure 1).

Assuming uncurbed greenhouse gas emissions—in line with the so-called scenario RCP 8.5 of the Intergovernmental Panel on Climate Change (IPCC)—the Arctic will remain ice-free for approximately seven months in the year 2100. In past decades, the summer Arctic sea ice still covered six million square kilometres, on average. The open waters of the future will create a whole new wave system. In addition, North Atlantic waves will expand unhindered into the Arctic Ocean (see figure 2). “The Northeast Passage would allow regular transit of ships in the summer. But where there is ice today, cargo ships would have to battle tall waves,” says Dobrynin.

Wave dynamics do not only influence the ice itself but also extend to a water depth of about 200 meters. Thus, the currently unspoilt seabed underneath the ice would be churned up with unknown ramifications for the local ecosystem (see figure 3). This development also affects the coastlines. Dobrynin shows that waves, for instance in the Laptev Sea, stir up more and more sediments. At the same time, they may erode adjoining permafrost land regions (see figure 4). “On top of global warming, this could accelerate the ice melt with the risk of releasing additional greenhouse gas emissions from permafrost,” explains Mikhail Dobrynin.

The researcher employs computational climate models to establish current and future wind and ice values for his prognoses. His results enable him to calculate various wave characteristics such as wave height, length, and friction velocity. The latter indicates the current-induced stress condition in the seabed. Subsequently, Dobrynin compares data for the periods from 2000 to 2010 and 2090 to 2100—all based on the assumption that greenhouse gas emissions will stay the same. In that case, the global temperature would rise by an average of four degrees Celsius until 2100. Similar but less severe effects will occur in the event of reduced emissions and a moderate temperature rise of two to three degrees.

More information:

• Video recording of the press conference
• Download figures:
  Figure 1: Characteristic pattern: wave-fractured Arctic sea ice
  Photo: UHH/CEN/Dobrynin
  Figure 2: An ice-free future. The average projected wave height increase due to the current average summer minimum (2000-2010) compared with future summers (2090-2100), white=sea ice, the average wave height at the North Pole will range between one and two meters
  Figure 3: Wave-induced stress in the seabed: shallow and coastal regions are particularly affected by higher waves (red and yellow).
  Figure 4: Permafrost soils: the coastal zone is further impacted and eroded by waves.
  Photo: Mikhail Grigoriev
  
  
  

Contact:

Dr. Mikhail Dobrynin
Center for Earth System Research and Sustainability (CEN)
E-Mail: mikhail.dobrynin"AT"uni-hamburg.de
Phone: +49 40 42838-7750
Universität Hamburg
Bundesstraße 53, 20146 Hamburg, Germany

Ute Kreis
Press/ Outreach
Center for Earth System Research and Sustainability (CEN), Cluster of Excellence CliSAP
E-Mail: ute.kreis"AT"uni-hamburg.de
Phone: +49 40 42838-4523
Universität Hamburg
Grindelberg 5, 20144 Hamburg, Germany