The motto of oceanography should be: “It’s not that simple.”
Dallas Murphy wrote that in a book containing his reflections from numerous voyages with ocean scientists, entitled Follow the Water: Exploring the Sea to Discover Climate. The author goes on to say:
“One reason why the ocean has been left out of the climate-change discussion is that its internal mechanisms and its interactions with the atmosphere are stunningly complex. That the ocean has been left out has helped pitch the discussion toward unproductive, distracting extremes–either global warming is bunk or sea levels are about to rise twenty feet–and to frame the issue as a matter of opinion, like the place of prayer in public schools.”
He also quotes respected Oceanographer Carl Wunsch: “One of the reasons oceanography has a flavor all it’s own lies in the brute difficulty of observing the Ocean.”
A previous post on the Climate Water Wheel referred to the metaphor of the ocean serving as a thermal flywheel in our planetary climate due to the massive storage of solar energy in bodies of water. Another post provided some basics on the dynamics of sea ice.
Now, in keeping with the motto above, we shall see that indeed, it is not that simple when we look more closely inside the Arctic Ocean. For example, consider this map from Woods Hole Oceanographic Institution (WHOI):
“Follow the water: Cold, relatively fresh water from the Pacific Ocean enters the Arctic Ocean through the Bering Strait. It is swept into the Beaufort Gyre and exits into the North Atlantic Ocean through three gateways (Fram, Davis, and Hudson Straits). Warmer, denser waters from the Atlantic penetrate the Arctic Ocean beneath colder water layers, which lie atop the warmer waters and act as a barrier preventing them from melting sea ice.
Once in the Arctic Ocean basin, the water is swept into a mammoth circular current—driven by strong winds—called the Beaufort Gyre (BG). Mighty Siberian and Canadian rivers also drain into the gyre to create a great reservoir of relatively fresh water. Winds trap this water in a clockwise flow, but periodically, the winds shift and the gyre weakens, allowing large volumes of fresh water to leak out. This is “the flywheel,” said WHOI physical oceanographer Andrey Proshutinksy, and when it turns off, fresh water flows toward the North Atlantic.
The water exits the Arctic Ocean via several “gateways.” It can flow through the Fram Strait, between northeast Greenland and Svalbard Island, and then branch around either side of Iceland. It can flow around the west side of Greenland through Baffin Bay and out Davis Strait. It may also flow through a maze of Canadian islands and out Hudson Strait.
These gateways are two-way: They also let in the warmer Atlantic waters that—if not for the halocline—could melt Arctic sea ice.”
The BG Flywheel System
The research indicates that the complexity can be imagined as a series of flywheels, interacting and combining to moderate the short term effects of weather and changes in circulations of water and winds. Note that this conception shows the ocean flywheel as having four components or layers that operate in their own patterns while being interconnected.
And, as the flywheel system depicts, the ocean components are stratified by both temperature and salinity (saltiness). When sea ice forms, it releases salt into surface waters. These waters become denser and sink to form the Arctic halocline, a layer of cold water that acts as barrier between sea ice and deeper warmer water that could melt the ice. (Illustration by Jayne Doucette, WHOI)
More from WHOI:
Summarizing several hypotheses introduced recently in the publications mentioned above we conclude that the oceanic BG is a major part of the Arctic climate system and is responsible for:
a) Stabilization of the anticyclonic circulation of sea ice and upper ocean layers
b) Accumulation and release of liquid fresh water and sea ice from the BG
c) Ventilation of the ocean in coastal polynyas and openings along shelf-break
d) Regulation of the circulation and fractional redistribution of the summer and winter Pacific waters in the Arctic Ocean
e) Regulation of pathways of the freshwater from the Arctic to the North Atlantic
The sea ice flywheel is an intermediate link between the atmosphere and ocean. Also, sea ice is a product of the atmosphere and ocean interactions. It transfers momentum from the atmosphere to the ocean modifying it depending on sea ice concentration, thickness and its surface and bottom roughness and regulates heat and mass exchange between the atmosphere and ocean. Sea ice flywheel of the system is responsible for:
a) Regulation of momentum and heat transfer between the atmosphere and ocean
b) Accumulation and release of fresh water or salt during melting-freezing cycle
c) Redistribution of fresh water sources through involvement of the first year ice from the marginal seas into the BG circulation and keeping it there for years and transforming it into highly ridged and thick multi-year ice under converging conditions of the BG ice motion.
d) Memorizing of the previous years conditions and slowing down variations in order to avoid abrupt changes
e) Protection of ocean from overcooling or overheating (the latter is extremely important for polar biology)
Our planet’s climate has changed so little over thousands of years that alarms have been sounded over less than 1 degree celsius of estimated average warming since the Little Ice Age ended 150 years ago. But actually, our Modern Warming period was preceded by the Medieval Warm period, the Roman, and the Minoan Warm periods. Each of them was slightly cooler than the previous, and all of them warmer than now.
If you are looking for explanations why our moderate climate persists over millennia and varies only within a tight range of temperatures, give a thought to the role of the Arctic flywheel system.
Of course, even this is far from the whole story. As the map above shows, there’s lots more than the Beaufort Gyre going on. For example, the Transpolar Current drives flows of ice and water on the European side, in addition to the Beaufort Gyre acting on the North American side.
And despite the emphasis above on the Pacific water, the Atlantic Gulf stream supplies most of the water entering the Arctic.
“The Arctic Ocean is permanently supplied with new water from the Gulf Current, which enters the sea close at the surface near Spitsbergen. This current is called the West Spitsbergen current. The arriving water is relatively warm (6 to 8°C) and salty (35.1 to 35.3%) and has a mean speed of ca. 30 cm/sec-1. The warm Atlantic water represents almost 90% of all water masses the Arctic receives. The other ~10% comes via the Bering Strait or rivers. Due to the fact that the warm Atlantic water reaches usually the edge of the Arctic Ocean at Spitsbergen in open water, the cooling process starts well before entering the Polar Sea.”
Reblogged this on CraigM350.
Reblogged this on and commented:
very insigthful and detailed analysis of a complex issue too simplified by authors and the media
First of all; congratulation to your immense efforts on this year sea ice season. It is not only well presented, but very timely, as the selected period indicates that claims about an ice-free Arctic Ocean look ignorant and incompetent.
Also the current post has my full appreciation, although I believe that the Arctic Ocean current system is largely due to the interior with an extreme complexity of temperature and salinity differences (see an image on water structure here: http://www.arctic-heats-up.com/pdf/7_1.pdf ), while wind has only a minor impact. I am not able to give any figures in this respect, but would like to mention two aspects:
__The highest wind force mange only to revolve the sea surface layer down to about 50 meters. The average depth is about 1000 meters.
__Over the four seasons the average ice cover is presumably well above 60% (my gross estimation), which diminish influence by wind accordingly.
Pushing the Arctic Ocean issue is well appreciated.
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Thanks Arnd for stopping by. I thought of you when I read about the suggested motto for oceanographers. Like this comment, you have a way of responding along these lines: “Yes but, there is also this, and this and this to consider.” I see now that is normal discourse in your profession in view of both the complexity and the research difficulties.
Thanks for the link; I think your Chapter 7 is much to the point http://www.arctic-heats-up.com/chapter_7.html.
Unfortunately there will be an hiatus in Arctic ice reporting after this week, as I will be seeing Greenland, Iceland, Faroe Islands and Norway for myself; on a ship, but entirely avoiding the difficulties mentioned by Carl Wunsch.
Unlike the global warming hiatus, I am certain the ice reporting will resume in August.
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WOOH! Last September I booked a hotel in NUUK from 30. July- 6. August 2015, which I cancelled two months ago, not really knowing what to do there. A pity – now I miss the chance to wave when you navigate along Greenland’s coast. Instead all best wishes for an interesting and safe journey and a happy return.
How ironic. We are scheduled to go ashore at Nuuk on July 30.
BTW, your diagram from Aagaard is illuminating also by showing the contours of the various basins, which also impacts on the dynamics.
Reblogged this on Climate Collections and commented:
Ron Clutz provides an excellent primer for Arctic ocean circulations understandable by all. The post includes a guest comment by the respected Arnd Bernaerts with links to some of his work.
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