Study: dust guided by meandering jet stream has big impact on Arctic melt

Polar jet circulation changes bring Sahara dust to Arctic, increasing temperatures, melting ice

Summary points

  • A new atmospheric mechanism by which dust travels from the Sahara Desert across the eastern side of the North Atlantic Ocean towards the Arctic has been discovered
  • The dust emission was generated by a Saharan cyclone that was triggered by the intrusion of a trough emanating from the polar jet
  • The poleward transport of warm dust was caused by a meandering polar jet stream
  • Approximately half of the warming in the Arctic is being attributed to increased moisture and heat fluxes transported to the region from lower latitudes

Abu Dhabi, October 10, 2018: Research scientists at NYU Abu Dhabi, along with other global researchers, have identified a new mechanism by which warm dust travels from the Sahara Desert to the Arctic Circle, which has been proven to affect rising temperatures and ice melt in Greenland.

Their findings highlight the role that the polar jet and associated atmospheric circulation plays in the transport of mineral dust from the Sahara desert to the Arctic across eastern side of the North Atlantic Ocean.

A meandering polar jet was discovered as responsible for both the emission and transport of dust from Northwest Africa to the Arctic. The emission has been linked to an intense Saharan cyclone that formed in early April 2011, which was caused by the intrusion of an upper-level trough emanating from the polar jet.

Meandering polar jet stream visible in red colors, upper-level trough visible in blue. CREDIT: ECMWF

The study has found that atmospheric circulation of this nature enables the transport of dust, warm and moist air masses from subtropics and mid-latitudes to the Arctic, where approximately half of the warming is now being attributed to increased moisture and heat fluxes transported to the region.

Rise in temperature and ice melt detected in Southeast Greenland, visible in red colors. CREDIT: ECMWF and AMSR-E

The warm and moist air masses accompanying the Saharan dust caused a rise in surface temperature of 10C for more than three consecutive days upon reaching southeastern Greenland. Subsequent temperature observations detected increased melting within the ice across this same area.

“The polar jet stream has been identified as the main driver for such events leading to the transport of large amount of dust to high-latitudes,” said Diana Francis, atmospheric scientist at NYU Abu Dhabi and lead research scientist in this study.

“If the polar jet is set to slow more frequently due to the changes in the Arctic climate system and to the Arctic Amplification, such events are expected to become more frequent,” Francis added.

The newly discovered poleward route is considered the most substantial in terms of dust load import into the Arctic, due to the minimal geographical distance between the origin point and the destination.

This is dust in natural color seen from space travelling towards Greenland. CREDIT: NASA

‘The impact of dust deposition on ice in Greenland, such as darkening ice and formation of algae on ice or cryoconite, as well as the link between Saharan dust transport and the Arctic heat dome must be investigated further in collaboration with scientists in UK and Germany’ Francis emphasized.

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The study: (open access)

Polar jet associated circulation triggered a Saharan cyclone and derived the poleward
transport of the African dust generated by the cyclone.

Abstract:

In this study, we identify a new mechanism by which dust aerosols travel over long distances across the eastern side of the North Atlantic Ocean toward the Arctic. The meandering polar jet was at the origin of both dust emission through cyclogenesis over Northwest Africa and poleward transport of the uplifted dust towards the Arctic, through cut-off circulation. The dust emission was associated with an intense Saharan cyclone that formed over Northwest Africa in early April 2011. The formation of the cyclone was caused by the intrusion into subtropics, of a high-latitude-upper-level trough, linked to the meandering polar jet. The trough initiated cyclogenesis over Northwest Africa after orographic blocking by the Anti-Atlas Mountains. The still meandering polar jet led to the formation of a cut-off low further south with which the Saharan dust-cyclone merged 2 days later and moved northward with the main stream. Beside satellite observations, a simulation at high resolution was performed using the prognostic-dust permitting model MesoNH.

The total dust load carried during this event to areas located north of 40 N was estimated by the model to be 38 Tg and dust deposition was estimated to be 1.3 Tg.

The Saharan dust reaching Greenland was accompanied by warm and moist air masses that caused a rise in surface temperature of about 10C for more than 3 consecutive days over the southeastern Greenland. Ice melt over this area of Greenland was detected in the brightness temperature observations.

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44 thoughts on “Study: dust guided by meandering jet stream has big impact on Arctic melt

    • Duh! You can’t discover ANYTHING by watching it happen, you have to model it to learn about it!

    • Here in London at 51.5 degree N, with the Arctic circle is just over 14 degrees further north at 65.8, from time to time we get the Sahara’s dust. The last one almost exactly a year ago (October 14, 2017) was discussed widely here on WUWT .

    • The mechanism is probably old, literally as old as the hills. 🙂

      Greenland ice cores contain layers of wind-blown dust that correlate with cold, dry periods in the past, when cold deserts were scoured by wind. link

      Wind blown desert dust making its way to Greenland is a well known phenomenon.

  1. The study has found that atmospheric circulation of this nature enables the transport of dust, warm and moist air masses from subtropics and mid-latitudes to the Arctic, where approximately half of the warming is now being attributed to increased moisture and heat fluxes transported to the region.

    Yeah but see if only we hadn’t been burning fossil fuels all this time the dust wouldn’t have been as hot as it was when it got there…

  2. It’s amazing!
    Transport Sahara dust to the arctic where it forms black soot like layers on the ice…

    38 Tg, as in Teragrams.

    Divided by 2,000, that become 19 billion metric tons.

    This truck carries approximately 400 tons (362.9 metric tons) of Earth.
    https://www.mining-technology.com/wp-content/uploads/sites/8/2017/10/3-image-Terex-6300AC.jpg

    Apparently, one jet stream loop carried enough Earth to the Arctic, to fill 52,356 of these trucks.

    It is still just weather.

      • The fact that parts of the ocean have all the iron it needs is proof that there are no parts that are short of iron?

    • I think your math is wrong? 1000 grams in a kilogram, 1000 kg in a metric ton, so need to divide by 2,000,000 for 19 million metric tons. Or 52 of those dump trucks. Of course, it only takes a few hundred micron-thick layer to be an issue, but it’s a bit more expected…

      • ShanghaiDan,

        You may want to check your math as well. There are 907,185 (rounded) grams in a 2000 lb. ton. So, 38Tg divided by 907,185 = 41,887,817 tons. If each truck carries a load of 400 tons, that would require 104,720 (rounded) loads…a few more than 52 😉

        • the very act of converting to a non metric ton is daft as they are more or less the same and where has the ‘2’ come from. A teragram is 1 million metric tonnes (looking it up is easier!! but 1000g in a kilo, 1000 kg in a tonne = /1,000,000) so 38,000,000,000,000g/1,000,000 = 38,000,000t.

          There are no road going trucks here in the uk carrying more than 40t (I think) so thats as near as dammit 1,000,000 trucks.

          Hope thats right now but does seem to be one helluva lot

      • ShanghaiDan,
        If you write anything criticizing another person’s arithmetical calculation, you will inevitably make a mistake of your own. This is Muphry’s Law.
        Peter

    • ATheoK – you are wrong. 1 teragram = 10^12 grams and 10^6 grams = 1 tonne, so 38 Tg = 38 × 10^6 tonnes. 38 megatonnes, not 19 billion tonnes. Sorry.

      The use of tera- and peta- prefixes is part of climate science culture. They make the numbers sound bigger and more scary, while actually imparting less readily accessible information than they would if they had used tons, megatons or gigatons.

      Also note the temperature scale on the map of Greenland. The bright, scary, blood-red colour just squeaks over 273°K. Not causing rivers of meltwater at that temperature.

      Everything about climate science is carefully calibrated to convey the message of impending doom.

      • Old and busted:
        How many angels can dance on the head of a pin?

        New and Hot:

        How many dump trucks of Saharan dust did the Jet Stream carry to Greenland?

    • FYI, 1 tonne (metric) = 0.9842 Imperial tons! DO you Virginian Colonists use a slightly different measure? AtB 😉

      • Us right thinkin’ Muricans use what you europeans call Short Tons. 2000lbs=1ton.

        1long ton= imperial units
        1ton= them fancy French units
        1 short ton= ‘Murican units

  3. There has been noticeable warming in the Arctic over recent days as a looping jet has linked with increased jet stream activity in the Arctic. To cause a large movement of warm air from mostly Russia to be drawn up into the Arctic. While at the same time the same sort of jet patterning has been drawing Polar air down across Canada and now over the northern Atlantic. l have been banging on about increased jet stream activity in the Arctic for a few months now.
    Because l knew that once we move towards winter to would aid large movement of the air masses to move in and out of the Arctic. When these movements of air become large scale then that limits there movement within the Arctic and so the flow of these air masses tend to get stuck over certain areas across the NH. Over recent weeks Canada has been stuck under the out flow of air from the Arctic.

  4. If Global warming pus all of its other names mean anything, then as its Global it must also affect the Antarctic. So did it. No of course not, its weather after all.

    MJE

  5. A meandering polar jet was discovered as responsible for both the emission and transport of dust from Northwest Africa to the Arctic. The emission has been linked to an intense Saharan cyclone that formed in early April 2011, which was caused by the intrusion of an upper-level trough emanating from the polar jet.

    Here is the dust cloud they observed west of Portugal on 06Apr2011

    In late March 2018 a cold outbreak drove Saharan dust from the Atlas mountains down to the south-west coast of Africa and on to Greece
    Long Range Dust Outbreak over Africa and Greece

    This is part of a developing pattern associated with the switch to the new climatic cycle of more meridional air mass movements.

  6. There will be a good example of the same type of jet stream patterning over Russia between the 15th-17th Oct.
    As a sharp kink in the jet stream forms and draws air from Arctic Russia down beyond Russia’s southern boarders.

  7. Wow…38 million metric tonnes in one storm is estimated to get blown off the Sahara, with 1.3 million tonnes getting blown to the Arctic. There won’t be anything left of the Sahara in a few million years.
    And 36.7 million more tonnes getting deposited from the Amazon to the global oceans in one storm. No wonder I can’t keep up with dusting the house any more.

    It was even worse in the Last Glacial Maximum when wind borne dust events are estimated to to be 20-25 more than present. With such low global CO2 concentrations and temps, there was much, much less plant life and far more deserts globally, with very nasty storms and inclement weather plus exposed continental shelves exposed with sea levels up to 125 M (410 feet) lower than present. Even with so much land in the NH covered by ice, there was a lot of additional land from lower sea levels exposed all over the planet with tree lines 20 degrees south of present. I doubt we would much recognize the climate from just 20,000 years ago. Except for the equatorial regions getting the bulk of the solar insolation, the rest of the planet was a dry, cold and windy place. And extremely dusty.

    I always wonder when looking at stratified soils that must have been deposited by airborne dust over millennium. Many areas of the world have clay/silt/sand deposits called Loess up to 1000 feet deep in China, or the red clays of Europe or even the fertile farm lands blown in from many miles away from the Mississippi when it collected a lot of silt and clay that when dried out, just blew away. When ancient cities like Troy were discovered, there was 9 levels of previous cities all buried covered by up to 25-30 feet of wind blown ‘dirt’ in only 5000 years or less. Deeper where alluvial soils washed in, along with cobble and rocks in the strata.

    Things don’t stay the same for long, and is probably true regarding our short term weather and climate observations the last 150 years. This is why I just can’t accept the AGW view of the world, especially the catastrophe part. Not from warming.

    • Do you have any specific reference for your comment? I do pollen analysis of Iberian Peninsula for the last glacial period and I do think there is more humidity than previously thought in the system…we do have a cold weather ! The trees are almost supressed, maybe some were protected in valleys….but some taxa point to a signal of humidity in the system! Also we can prospect the blowing winds from Morrocco by identifying the Cedrus sp. which are quite common! Anyone could explain this humidity in a cold system instead of the aridity?

      • Not sure I understand your exact point, but the Iberian Peninsula isn’t the whole world. It is well understood that at the Last Glacial Maximum, atmospheric water vapor and humidity was less overall because the planet was much colder during the depths of the LGM. Just a basic function of reduced water carrying capacity of the colder atmosphere and less evaporated water in the system. Atmospheric water vapor, humidity and warmth that was generated in equatorial regions had a higher temperature differential and gradient to move weather to the polar regions with much faster weather systems. The water precipitated out as snow due to the colder climate in the polar regions, and was exacerbated through coalescence with the water vapor by so much extra dust in the atmosphere which led to also less water vapor and to further growth of the ice sheets.

        The imbedded dust in the ice caps helped accelerate the melting through increased albedo once the orbital mechanics shifted to a warmer climate, which ultimately led to higher temperatures and more water vapor and higher humidity levels which led to more rain on the ice sheets, melting them even faster. I know, it is always more complicated than this short paragraph, but I think it is well established that water vapor and humidity levels were much less during the time of the full blown ice age.

  8. ShanghaiDan,

    You may want to check your math as well. There are 907,185 (rounded) grams in a 2000 lb. ton. So, 38Tg divided by 907,185 = 41,887,817 tons. If each truck carries a load of 400 tons, that would require 104,720 (rounded) loads…a few more than 52 😉

    • Since he/she specifically said “metric ton” you’re incorrect regarding your criticism of his calculation. That would be 2,204.62 lbm per metric ton.

      You also won’t find many dump trucks that carry 400 tons. Mining dump trucks can be that large; the Belaz 75710 is the world’s largest, per Google, with a capacity of “496t”, which appear to be metric tons.

      A commercial over-the-road dump truck has a capacity of 10-14 cubic yards. Sand weighs 120 lbm/cubic foot, or 3,240 lbm/cubic yard, giving your dump truck a range of 32,400 – 45,360 lbm, or 16.2 to 22.7 tons (American) per load. At the high end of the capacity range, to move that 83,775,560,000 lbm ([(38,000,000,000,000g /1000g/kg) x 2.20462 lbm/kg] would require 1,846,904 truck loads.

      Going back to the Belaz, you would need (38,000,000,000,000 g / 1,000 g/kg / 1,000 kg/t / 496 t/load) or 76,613 truckloads.

  9. Contrary to the CO2 news discourse on primary causes of snow melting in Greenland, recent research shows how accumulating soot (some from Indonesian palm oil clearing fires) in the snow – causes albedo change after the darkening of the arctic surface. Absorbing more heat from the sun, the rate of melting snow increases (Tedesco et al., 2016). Tedesco, T., Doherty, S., Fettweis, X., Alexander, P., Jeyaratnam, J., & Stroeve, J. (2016). The darkening of the Greenland ice sheet: Trends, drivers, and projections (1981– 2100). Cryosphere (The), 10(2016), 477–496.

    • Thank you David.
      Interesting, even though the word ‘simulation’ appears, because they seem to have *measured* an actual change in albedo.

      What that does is NOT the problem (melts a bit more ice than usual)

      The Problem is that that dust & soot represent a net loss from somewhere else on the planet.
      I assert that the dust is coming from increasingly intensive agriculture – it is a loss from farmland.
      Where else is it coming from? The amount coming from existing deserts would be constant, *not* increasing as your linked paper says.
      Also, and no-one is entirely sure why, but soot is a very good soil-fertility enhancer.

      Realise that dust from farmland will bring large amounts of potassium & phosphorus (from the fertiliser farmers use) AND that the dust will be landing anywhere and everywhere around the globe.
      Add fertiliser to places that are normally deprived of such stuff and what do you get -Global Greening.

      The same dust/soot has different effects depending where it lands.
      It all fits and what it represents is the depletion (erosion) of farmland soils.
      Sod the ice in some far-flung remote place.
      We need to be looking after our own backyards first and foremost.

      I get 38 teragrams to 38.0 million tonnes (metric)
      =37.4 million long tons (UK)
      =41.9 million short tons (US)
      (Rounded to one decimal)

      The paranoia is nicely displayed by a vaguely remembered figure of mine
      These folks think 39 megatonnes will destroy the world yet ‘normal’ human excavating (roads, houses, dredging, mining, dam building etc) move annually in excess of 57,000 million tonnes (57 gigatonnes)
      Hence the large dumper trucks.

      Strangely, the world still appears to be here. What is worryingly strange is the behaviour of its inhabitants. There *is* a reason for that also.
      Strangely enough, it’s “blowing in the wind”

      And since when did ice *seriously* start melting at temps below 275Kelvin?
      Somebody please help these people. Wake them up before they do something *really* stupid and consign the rest of us to the dustbin of history

      “Dustbin”
      Haha, ain’t English such a beautiful tongue?

      • “And since when did ice *seriously* start melting at temps below 275Kelvin?”

        It’s not melting; it’s subliming, going directly from solid to vapor. Happens all the time, especially when a dry 0°F wind is blowing. We’d wake up in Denver and find that all the accumulated snow was gone from our roads. Your ice cube tray can also confirm this process.

  10. Judith Curry has an interesting article on her blog entitled ‘Beyond Milankovitch’ where it is postulated that increased solar output allied to dust blown from Gobi/Taklamaken deserts to ice fields is the trigger for escape from Ice Ages.

    The data is based on ice core analysis and shows cyclical pulses of dust deposition.

  11. It would be interesting to compare the volume of the dust from natural sources to the human-caused soot from power plants as well as from diesel cars and trucks.

    • Another factor is algae that grows in the bottom of flat sea-ice. When ice is flipped like a pancake the bottom is “dirty”. (This occurs when sea-ice allows some sunlight through. Huge and very-thick icebergs have cleaner bottoms.) (Time for a rude joke, but I won’t go there.)

  12. “It came from AGU” says enough!

    [AMSR-E stopped rotating, dropped down to 2rpm, on 4 Oct. 2011. At 2rpm the “data” were used as ‘engineering’ but had to be stopped due to vibrations to Aqua.]

  13. This study confirms what others have suggested in other ways. But air temperatures and albedo are less effective at melting sea-ice than the water under the ice.

    The way air can melt a lot of sea-ice in a hurry is when the same meridional pattern that blows the Sahara dust up into the arctic blows a large amount of sea-ice south through Fram Strait. The most interesting example of this occurred in 1817, and resulted in ice-bergs around Ireland, but waters north of Greenland surprisingly ice-free. This is from a report written by the British Admiralty at that time:

    “From an examination of the Greenland captains, it has been found that owing to some convulsions of nature , the sea was more open and more free from compact ice than in any former voyage they ever made: that several ships actually reached the eighty-fourth degree of latitude, in which no ice whatever was found; that for the first time for 400 years, vessels penetrated to the west coast of Greenland, and that they apprehended no obstacle to their even reaching the pole, if it had consisted with their duty to their employers to make the attempt.”

    https://sunriseswansong.wordpress.com/2018/10/07/arctic-sea-ice-resupply-problems/

  14. Here in Texas and Louisiana we had a LOT of Saharan dust in the air just a few months ago. It’s not just a polar phenomenon.

    And as the deserts recede due to CO2 fertilization, dust becomes less of a problem over the long haul.

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