Greenland ice stream retreated during a cold period of climate


Ice stream retreats under a cold climate

Why did the Jakobshavn Isbræ ice stream in West Greenland retreat under a cold climate period called the Younger Dryas?

A research article, published in Nature Communications, shows that a warmer ocean surface in central-eastern Baffin Bay triggered the ice retreat during this cold period. The Younger Dryas period occurred 12,900-11,700 years ago and interrupted the atmospheric warming after the last ice age.

The Younger Dryas cold interval as viewed from central Greenland. From: Quaternary Science Reviews Volume 19, Issues 1-5, 1 January 2000, Pages 213-226. Richard B. Alley

Diatoms reveal warm ocean surface in central-eastern Baffin Bay

The published study uses marine fossil diatoms preserved in the sediments to reconstruct past sea surface conditions, including sea surface temperatures, sea ice variability and ocean currents. Diatoms were studied from a ca. 7-meter long sediment core recovered from the ocean floor in 2008. Such sediment cores are windows to the past climate. According to the study, the warmer sea surface temperatures and less-extensive sea ice cover during the Younger Dryas were caused by an enhancement of warmer Atlantic-sourced water inflow to Baffin Bay and increased solar insolation in the Northern Hemisphere.

Understanding climate change

Today, Jakobshavn Isbræ is one of the largest ice streams in Greenland, draining ca. 7% of the ice volume and producing 10% of Greenland’s icebergs. Thus it is a significant contributor to the Greenland Ice Sheet´s mass balance.

A fast-flowing ice stream at Upernavik, Northwest Greenland, terminating in Baffin Bay. The ice stream is recognizable by its heavily crevassed ice next to the smoother, slower-moving ice. Photo credit: Niels J. Korsgaard.

– Interactions between ocean, ice sheet and atmosphere are not well understood, yet they are crucial for climate models and for predicting the impacts of the ongoing climate change, says Mimmi Oksman, a researcher at the University of Helsinki and one of the authors of the article.

The results emphasize the importance of the interaction between the ocean and the Greenland Ice Sheet under the ongoing climate warming, showing that a warming ocean can have a drastic influence on the marine-terminating glaciers of Greenland.


The paper:

40 thoughts on “Greenland ice stream retreated during a cold period of climate

    • Exactly right. Too cold to carry lots of warm, moisture laden air, ergo, less snow, ergo, not enough deposition to push that sucker down the hill.

  1. A better question is what makes this “stream” move much faster than adjacent ice? Then questions as to how that mechanism was affected could be determined and studied to see how the flow reacted.

  2. You gotta love these guys that promote their papers…and finance stream… saying it’s not understood

    “Interactions between ocean, ice sheet and atmosphere are not well understood,”

    ….undermining everything the model promoters say

  3. Isn’t this obvious?

    Lower temperatures -> less evaporation -> less precipitation?

    When you look at any of the ice core data, the number of years per fixed width slice of core (sometimes called a bag) is inversely proportional to the temperature.

  4. Why did the Jakobshavn Isbræ ice stream in West Greenland retreat under a cold climate period called the Younger Dryas?

    lag time differences associated with the significant mass balance variables.

    Why is the sky blue?

  5. Sigh, more press-release “science”. The only new thing is the CAGW slant. Actually the Greenland ice advanced along most of its periphery during the Younger Dryas. Disko bugt is the exception. There the ice retreated during the first few centuries, then there was a brief advance during Mid Dryas, followed by a very fast retreat:

    And the Jakobshavn isbrae didn’t even exist during Younger Dryas. It only formed when the ice had retreated behind the coast and the Disko bay Ice Stream became channeled through the Illulissat fjord.

    • Shhhh… Someone may hear that and they will lose all their funding from the ignorant people funding it.

  6. Again… another pronouncement of “the way things were” based on an analysis
    of ONE core from ONE place.

    • No. It is an analysis of the historical sea temperatures in the location from where the sample was taken. The paper makes no attempt to extrapolate to different locations.

  7. I still think that the proximate cause of the Younger Dryas may have been a bolide or impact event; did she account for this possibility?

    • Why would she, when there is zero actual evidence for that baseless conjecture?

      The YD is no different from the Older and Middle Dryas and all the other rapid cooling events during the last termination and the previous ones of the Pleistocene.

  8. This is all based on diatom species and species ratios. It is bad enough people “adjusting” measured temperature data, but claiming a relative precise temperature or even general temperature from diatoms in a sediment core, well—— Diatoms are surface dwelling creatures, part of the phytoplankton therefore carried by surface currents and their remains upon death moved around by subsurface currents, currents most probably with a different temperature regime that the surface currents. So a sediment core from relatively deep water is measuring diatoms from where exactly? And how does anyone know what the temperatures tolerances of a given diatom species 10+K ago? A satellite specialists/ oceanographer friend once told me that when he was in graduate school that no one ever worried about doing more research on the Gulf Stream current system until we put the first satellite up looking back at that system. Warm core and cold core eddies before satellites were believe very rare and unusual events. After satellites they knew it was just the opposite the Gulf Stream system, most boundary currents, are defined by eddies and eddy formation, cold and warm.

    • Anybody checked the northern Baffin Bay surface temperatures in that same period?

      ‘Thermohaline circulation drives a global-scale system of currents called the “global conveyor belt.” The conveyor belt begins on the surface of the ocean near the pole in the North Atlantic. Here, the water is chilled by arctic temperatures. It also gets saltier because when sea ice forms, the salt does not freeze and is left behind in the surrounding water. The cold water is now more dense, due to the added salts, and sinks toward the ocean bottom. Surface water moves in to replace the sinking water, thus creating a current.’

      A colder north would create more sinking water so more surface water moves in to replace the sinking water, thus creating a stronger ‘warm’ surface current, full of warm water surface dwelling creatures.

      • ‘The conveyor belt is also a vital component of the global ocean nutrient and carbon dioxide cycles. Warm surface waters are depleted of nutrients and CARBON DIOXIDE, but they are enriched again as they travel through the conveyor belt as deep or bottom layers. The base of the world’s food chain depends on the cool, nutrient-rich waters that support the growth of algae and seaweed.’

        So what is all that talk about ocean acidification ?

  9. If you go through the data presented in this study, one might conclude the authors just made up a proposition which is almost falsified by the data shown. The actual data from the particular core doesn’t show the glaciers slowed down. Dropstones and thicker sedimentaton from ice-bergs are evident in the Younger Dryas period indicating increased glacial flow. I hate these guys.

  10. Who translated this? “Ice stream?” “.ca?,” does this mean Approximately? Can we say Glacier?

    Every article based on any kind of climate proxy should have error bars prominently displayed.

    Diatoms? A Good proxy or a Bad proxy?

    Are there any good ones???

    • “Ice stream” is a quite common term in glaciology, while “ca” is the normal abbreviation for latin circa “around” in non-anglophone countries.

  11. Diatoms and warm water in the Younger Dryas, baloney. The atmosphere was dry and a thousand years of sublimation and no snow did it. I’m sure the ice retreated on Kilimanjaro, too, like it did causing all the end of world fuss a decade ago, unless, of course the diatoms made an assault there too!

  12. Need to finally put to rest the myth that the Younger Dryas was a period of cooling. On the contrary it was a period of rapid warming at the close of an ice age that flooded the North Atlantic with meltwater that produced a faux indication of cooling in the Greenland ice cores. This ain’t rocket science, people!

    • Try that fairytale on someone else. I’ve spent a fair part of my life on the huge end-moraine system built up by the expanding Scandinavian ice-cap during Younger Dryas. And by the way, do you know why it is called “Dryas”? It is because the pine and birch forests in southern Scandinavia were killed by the cold and replaced by an arctic heath dominated by Mountain Aven Dryas octopetala. This was noted very early by scandinavian geologists who named this very cold interval after it.

      And how about the icecap in western Scotland during the Younger Dryas? Or the many corrie glaciers in Ireland? Were they caused by warming too?

      • Yes and no, they mark the maximum extent of the glacier, where expansion turned to retreat, or a reasonably long standstill during a retreat. Retreating glaciers only leave a thin structureless veneer of ground moraine.

        In rare cases a retreating glacier may expand enough on an annual basis to form series of small end moraines, so called annual moraines or de geer moraines. This probably only happens to ice-sheets that are grounded in shallow water.

        If you visit a modern glacier you will very often find a pronounced end moraine a few hundred to a few thousand meters in front of it. This marks the maximum extent of the glacier at the end of the “Little Ice Age”, c. 1700-1850 (the exact date varies geographically). The next end moraine outwards is, as a matter of fact, often from the Younger Dryas, at least in the Northern Hemisphere.

    • It means snow for Greenland, water for Norway, and cold in New England. Right?

      It also means Iceland low – Azores high is still the state of climate?

      • Azores high is still the state of climate?
        Azores high is there, though most of the weather in the northern region is being westerly driven – Atlantic storms aplenty. To the south (across east from Portugal) the Azores high is winning out. However the weather models are forecasting for the Azores high to shift westward (to the mid Atlantic) next week, giving most of Europe a very cold and wet west, NW blast.

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