In the coming decades, the Arctic Ocean will change dramatically from a calm, ice-covered sea to a more open ocean with stronger currents. This will affect the ecosystems in the Arctic and the global climate, according to new research published in Nature Communications.
On an ice floe in the central Arctic Ocean, there is intense research activity. The research vessel Kronprins Haakon has stopped so that researchers can take measurements over the next 24 hours.
Climate scientist Morven Muilwijk is deploying an instrument to measure the ocean currents beneath the ice floe he is standing on. He knows that the currents he is measuring today will be very different in a few years.
NPI ARCTIC OCEAN CRUISE 2024: Climate scientist Morven Muilwijk (left) is deploying an instrument to measure the strength and direction of ocean currents at various depths while it hangs under the ice. Here with colleague Zoe Koenig. Photo: Trine Lise Sviggum Helgerud, Norwegian Polar Institute
– We are here now taking measurements of the current state of the Arctic Ocean, while also working on future projections that show the area is changing rapidly. Our latest study clearly shows that the physics and ecosystems of the Arctic Ocean will change significantly in the next 10, 50, and 75 years, says Muilwijk.
The new study is published in the renowned journal Nature Communications, led by researchers from the Norwegian Polar Institute and GEOMAR in Germany, with Morven Muilwijk at the forefront. The calculations showing what the future Arctic Ocean will look like are made using the same climate models used in the IPCC’s Sixth Assessment Report.
– The models show that as the Arctic Ocean continues to warm due to global warming, wind speeds will increase, and sea ice will decrease. Our study focuses on the consequences of this.
Nature Communications: Future sea ice weakening amplifies wind-driven trends in surface stress and Arctic Ocean spin-up.
Less ice affects ocean currents
The sea ice in the Arctic acts as a stable lid that shields the water masses from direct wind influence for much of the year. Today, the Arctic Ocean is a calm sea with weak currents and little mixing.
With less area covered by sea ice due to climate change, the ocean becomes more exposed to wind. Additionally, stronger winds will enhance surface currents, eventually leading to movement deeper into the water column.
– Stronger winds and less sea ice mean that more energy is transferred from the atmosphere to the ocean, with significant consequences for ocean circulation and stratification in the Arctic Ocean.
The study shows that there could be a 38% increase in wind influence on the ocean surface by the end of the century (2100), with some models suggesting increases of up to 72% compared to today.
The figure explains the findings of the new study published in Nature Communications
New findings on wind energy
The researchers have uncovered a new, important mechanism: a weaker ice cover amplifies the effect of increased wind, leading to even stronger energy transfer from the atmosphere to the ocean. Previously, a significant portion of the wind energy was absorbed by the thick, rigid ice cover, which, among other things, led to the formation of pressure ridges in the ice.
– As the ice cover becomes thinner and more mobile, it absorbs much less wind energy. Instead, the wind energy is transferred more directly through the ice to the ocean, says the researcher.
WIND INFLUENCE: The researchers behind the study have calculated that there could be a 38% increase in wind influence on the ocean surface by 2100. The Arctic Ocean will change from a calm, ice-covered sea to a more open and dynamic ocean. Photo: Trine Lise Sviggum Helgerud, Norwegian Polar Institute
Sea ice can melt from below
The researchers on the Arctic Ocean cruise 2024 are mapping the current state of the Arctic Ocean. There are few observations from this area, but it is precisely here that the effects of global climate change will be greatest.
The current state (called the baseline) will therefore serve as a reference to measure changes. Establishing a baseline is crucial for assessing the impact of climate change over time.
The Arctic Ocean, as researchers know it today, has a distinct stratification in the water column, with fresh, cold polar water at the surface and salty, warm Atlantic water deeper down.
The polar water has a lower density than the salty Atlantic water and therefore sits higher in the water column. The models show that stronger wind influence will alter this distinct stratification in the Arctic Ocean.
– The warm water will mix upward from the depths and can contribute to melting the sea ice from below. This, in turn, reinforces the ongoing changes due to global warming, explains Muilwijk.
Ecosystems will change
Changes in ocean stratification will affect marine life. The mixing controls how nutrients are distributed in the water column. With increased mixing, nutrients from the depths are stirred upwards and become available to phytoplankton living in the upper 50 meters of the water.
Phytoplankton rely on nutrients and light to perform photosynthesis, just like plants on land, and they serve as food for the rest of the food chain. When phytoplankton have better conditions to grow, it creates ripple effects throughout the entire ecosystem.
Map: Anders Skoglund, Norwegian Polar Institute
Can affect global climate
Ocean currents transport large amounts of energy around the Earth, influencing the global climate. One example is the warm Gulf Stream, which contributes to the milder climate in Northern Europe compared to Alaska, which is at similar latitudes. The Gulf Stream is one of several ocean currents in the North Atlantic, which is sensitive to changes further north.
– As stronger ocean currents develop in the Arctic Ocean, the distribution of cold freshwater will change, which in turn affects ocean circulation in the North Atlantic and thus the climate of the Northern Hemisphere, says Muilwijk.
The new research will give climate scientists a deeper understanding of the relationship between sea ice, the ocean, and the atmosphere, and this insight can influence future climate modeling and research on the Arctic Ocean. Additionally, this knowledge can be used to plan how we should manage these areas in the future.
The study is published in the journal Nature Communications, which publishes high-quality peer-reviewed research. The study is open access, freely available, and has free usage rights for all.
Muilwijk, M., Hattermann, T., Martin, T. et al. Future sea ice weakening amplifies wind-driven trends in surface stress and Arctic Ocean spin-up. Nat Commun 15, 6889 (2024). https://doi.org/10.1038/s41467-024-50874-0
The research is funded by the EU project CRiceS through the Horizon 2020 program.
The researchers behind the new study are climate scientist Morven Muilwijk (Norwegian Polar Institute) (pictured), oceanographer Tore Hattermann (Norwegian Polar Institute), sea ice researcher Mats Granskog (Norwegian Polar Institute), and oceanographer Torge Martin (GEOMAR). Photo: Trine Lise Sviggum Helgerud, Norwegian Polar Institute
