New study: Ocean-driven warming along the western Antarctic Peninsula needs to be considered as part of a natural centennial timescale cycle of climate variability

Map of Antarctica indicating location of Antar...

Map of Antarctica indicating location of Antarctic Peninsula. (Photo credit: Wikipedia)

From Cardiff University:

Tiny fossils hold answers to big questions on climate change

Research explores 12,000 year fossil record

The western Antarctic Peninsula is one of the fastest warming regions on the planet, and the fastest warming part of the Southern Hemisphere.

Scientists have debated the causes of this warming, particularly in light of recent instrumental records of both atmospheric and oceanic warming from the region. As the atmosphere and ocean warm, so the ice sheet (holding an equivalent of 5 metres of global sea level rise, locked up in ice) becomes vulnerable to collapse.

Now research led by Cardiff University published in Nature Geoscience has used a unique 12,000 year long record from microscopic marine algae fossils to trace glacial ice entering the ocean along the western Antarctic Peninsula.

The study has found that the atmosphere had a more significant impact on warming along the western Antarctic Peninsula than oceanic circulation in the late Holocene (from 3500-250 years ago). 

This was not the case prior to 3500 years ago, and is not the case in the modern environment. The study has also shown that this late Holocene atmospheric warming was cyclic (400-500 year long cycles) and linked to the increasing strength of the El Niño – Southern Oscillation phenomenon (a climate pattern centred in the low latitude Pacific Ocean) demonstrating an equatorial influence on high latitude climate.

Dr Jennifer Pike, School of Earth and Ocean Sciences said: “Our research is helping to understand the past dynamic behaviour of the Antarctic Peninsula Ice Sheet. The implications of our findings are that the modern observations of ocean-driven warming along the western Antarctic Peninsula need to be considered as part of a natural centennial timescale cycle of climate variability, and that in order to understand climate change along the Antarctic Peninsula, we need to understand the broader climate connections with the rest of the planet.”

Ice derived from land has a very distinctive ratio of oxygen isotopes. This research is the highest resolution application in coastal Antarctic marine sediments of a technique to measure the oxygen isotope ratios of microscopic marine algae fossils (diatom silica). When a large amount of glacial ice is discharged into the coastal ocean, this alters the oxygen isotope ratio of the sea water that the marine algae are living in. This creates a clear imprint in the fossils that reveals the environmental conditions of the time. The scientists used the oxygen isotope ratio of the fossils to reconstruct the amount of glacial ice entering the coastal ocean in the past 12,000 years, and to determine whether the variations in the amount of ice being discharged were the result of changes in the ocean or atmospheric environment.

Professor Melanie Leng, from the British Geological Survey and Chair of Isotope Geosciences in the Department of Geology, University of Leicester, said: “Technologically the analysis of the oxygen isotope composition of diatom silica is extremely difficult, the British Geological Survey is one of a very few research organisations in the world that can undertake this type of analysis. For this research project the methodology has been developed over the last five years with the specific aim of investigating the different amounts of melting in the polar regions. It’s fair to say we are world leading pioneers in this technique.”

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The research is co-authored with Cardiff University by the universities of Nottingham, Leicester and the British Geological Survey and was funded by the Natural Environment Research Council (NERC).

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Glacial discharge along the west Antarctic Peninsula during the Holocene

Jennifer Pike, George E. A. Swann, Melanie J. Leng & Andrea M. Snelling

Abstract:

The causes for rising temperatures along the Antarctic Peninsula during the late Holocene have been debated, particularly in light of instrumental records of warming over the past decades1. Suggested mechanisms range from upwelling of warm deep waters onto the continental shelf in response to variations in the westerly winds2, to an influence of El Niño–Southern Oscillation on sea surface temperatures3. Here, we present a record of Holocene glacial ice discharge, derived from the oxygen isotope composition of marine diatoms from Palmer Deep along the west Antarctic Peninsula continental margin. We assess atmospheric versus oceanic influences on glacial discharge at this location, using analyses of diatom geochemistry to reconstruct atmospherically forced glacial ice discharge and diatom assemblage4 ecology to investigate the oceanic environment. We show that two processes of atmospheric forcing—an increasing occurrence of La Niña events5 and rising levels of summer insolation—had a stronger influence during the late Holocene than oceanic processes driven by southern westerly winds and upwelling of upper Circumpolar Deepwater. Given that the evolution of El Niño–Southern Oscillation under global warming is uncertain6, its future impacts on the climatically sensitive system of the Antarctic Peninsula Ice Sheet remain to be established.

Figure 2: Morlet wavelet analysis of ODP Site 1098 δ18Odiatom record

Morlet wavelet analysis of ODP Site 1098 [delta]18Odiatom record.

The upper panel shows the δ18Odiatom record and the lower panel shows the wavelet power spectrum. Shaded contours represent normalized variances and black lines surround statistically significant regions that exceed 95% confidence

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23 thoughts on “New study: Ocean-driven warming along the western Antarctic Peninsula needs to be considered as part of a natural centennial timescale cycle of climate variability

  1. Professor Melanie Leng, from the British Geological Survey and Chair of Isotope Geosciences in the Department of Geology, University of Leicester, said: “Technologically the analysis of the oxygen isotope composition of diatom silica is extremely difficult, the British Geological Survey is one of a very few research organisations in the world that can undertake this type of analysis.

    So don’t expect replication any time soon.

  2. More warming with more El Niños? Isn’t that exactly what Bob Tisdale has found over recent decades? I can see a Romm’s and Foster’s heads exploding now.

  3. “So don’t expect replication any time soon.” Yep, vaccinated ante hoc against falsification by adhockery, “I am the only one professional enough to …” (Ex-DEA Special Agent Lee Paige as he shot himself in the foot.) Leng should take note.

  4. “our findings are that the modern observations of ocean-driven warming along the western Antarctic Peninsula need to be considered as part of a natural centennial timescale cycle of climate variability”

    Little by little the “consensus” morphs.

  5. So they are not sure what the effect of global warming on ENSO WILL be. They don’t appear to realize that they have the larger picture – a series of multicentennial global warmings themselves! Also, they still are sticking the Hoaky stick in the present – mustn’t mess with Mikey’s hottest of the hottest.

  6. Bob Tisdale says:
    January 23, 2013 at 5:13 am

    On the other hand, had the results gone the other way, you’d be among the first to proclaim this ground breaking research that must be heeded by all.

    BTW, every proxy study such as this only covers the immediate area around the study. We can’t all claim that a single tree represents the entire world.
    When you add all the proxies together, you get a view of what the world is doing. And it shows that the recent past is not unusual.

  7. It looks an interesting study and it doesn’t make massive claims or sweeping generalizations. Its work like this which will gradually replace speculation. Small steps but important ones.

  8. They know damn well it’s the volcanoes warming the area. but – hey – they need the funding to they can swan around in the antarctic some more.

  9. They are using a proxy for amount of land based ice that melted in the sea.
    This would suggest more about glacial growth, than ocean temperature to me.
    It could be a proxy for increased precipitation over Antarctic, with suitable time-lag.
    When the sea surface temperature data has an adequate time base and satellites fully cover the globe,I will be very interested in the full picture of ocean heat flow.

  10. Meanwhile Antarctic sea ice extent is matching last year’s record levels. It’s worse than we thought.

  11. Boy, i’d like to see the article.

    “We show that two processes of atmospheric forcing—an increasing occurrence of La Niña events5 and rising levels of summer insolation—had a stronger influence during the late Holocene than oceanic processes driven by southern westerly winds ”

    I suppose they derive summer insolation from meltwater. A bit of tautology. Increasing La Nina’s=rising summer insolation at the Antarctic Circle?

    So 18O in carbonate=temperature and 18O in silicate=meltwater. Mmmmm…

  12. ‘Dr Jennifer Pike, School of Earth and Ocean Sciences said: “Our research is helping to understand the past dynamic behaviour of the Antarctic Peninsula Ice Sheet. The implications of our findings are that the modern observations of ocean-driven warming along the western Antarctic Peninsula need to be considered as part of a natural centennial timescale cycle of climate variability, and that in order to understand climate change along the Antarctic Peninsula, we need to understand the broader climate connections with the rest of the planet.”’

    This quotation expresses a healthy shift in emphasis toward science and away from speculation. Maybe WUWT cannot take credit for this shift but WUWT was the first to explain the need for this shift and has expressed it consistently for years. “Natural centennial timescale cycle of climate variability” is music to the ears of all scientists. Physical hypotheses about natural regularities are now in the forefront of discussions about climate. That alone will move science out of the nightmare of CAGW. As for policy making, that is something that seems beyond all rational thought at this time.

  13. Bob Tisdale says:
    January 23, 2013 at 5:13 am
    “All of that work for such a tiny portion of the globe. Remarkable.”

    You should expand your comment. In my opinion, such extensive work is necessary for genuine science. I am not endorsing their conclusions. I am endorsing their efforts, especially their efforts to follow scientific method. Their efforts might be imperfect. Someone said that the Hockey Stick is in their work; if that is true then it is very worrisome.

  14. Doug Huffman says:
    January 23, 2013 at 5:46 am

    It’s not that bad, is it? They are putting their scientific specialty on stage and it will get evaluated in light of their work. They are creating hypotheses that treat ENSO as a natural process; that is a qualitative change from the modeling mainstream who do not treat ENSO as a natural phenomenon that exists apart from their models.

  15. ‘Given that the evolution of El Niño–Southern Oscillation under global warming is uncertain, its future impacts on the climatically sensitive system of the Antarctic Peninsula Ice Sheet remain to be established.’

    In other words , we ticked the compulsory AGW scare box now can we have some more cash please .

  16. rising levels of summer insolation

    I wonder how they determined this. If correct, it implies natural cycles in cloud cover.

    BTW, the much hyped Antarctic Peninsula warming comes from a single British station, and all the warming was in minimum temperatures, which makes me suspicious they took their own little bit of anthropogenic warming with them to the Antarctic. A mini Urban Canyon Effect?

  17. This studies methodology makes me a bit skeptical. The mechanism connecting the measured data with the targeted phenomena is far too complicated.

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