Antarctic Peninsula ice more stable than thought

Posted: May 2, 2017 by oldbrew in climate, research
Tags: ,

Credit: coolantarctica.com


Another alleged climate alarm looks more like a damp squib, undermined by new research.

Glacier flow at the southern Antarctic Peninsula has increased since the 1990s, but a new study has found the change to be only a third of what was recently reported, says Phys.org.

An international team of researchers, led by the UK Centre for Polar Observation and Modelling at the University of Leeds, are the first to map the change in ice speed. The team collated measurements recorded by five different satellites to track changes in the speed of more than 30 glaciers since 1992.

The findings, published today in Geophysical Research Letters, represent the first detailed assessment of changing glacier flow in Western Palmer Land—the southwestern corner of the Antarctic Peninsula.

The new Leeds led research calls into question a recent study from the University of Bristol that reported 45 cubic kilometres per year increase in ice loss from the sector. The Leeds research found the increase to be three times smaller.

Lead author Dr Anna Hogg, from the Leeds’ School of Earth and Environment, said: “Dramatic changes have been reported in this part of Antarctica, so we took a closer look at how its glaciers have evolved using 25 years of satellite measurements dating back to the early 1990s.”

The researchers found that between 1992 and 2016, the flow of most of the region’s glaciers increased by between 20 and 30 centimetres per day, equating to an average 13% speedup across the glaciers of Western Palmer Land as a whole.

These measurements provide the first direct evidence that Western Palmer Land is losing ice due to increased glacier flow—a process known as dynamical imbalance.

The team also combined their satellite observations with an ice flow model using data assimilation to fill in gaps where the satellites were unable to produce measurements. This allowed the complete pattern of ice flow to be mapped, revealing that the regions glaciers are now pouring an additional 15 cubic kilometres of ice into the oceans each year compared to the 1990s.

The earlier study reported that the region was losing three times this amount of ice, based on measurements of glacier thinning and mass loss determined from other satellite measurements. The Leeds study casts doubt on that interpretation, because the degree of glacier speedup is far too small.

Study co-author Professor Andrew Shepherd, from Leeds’ School of Earth and Environment, explained: “Although Western Palmer Land holds a lot of ice—enough to raise global sea levels by 20 centimetres—its glaciers can’t be responsible for a major contribution to sea level rise, because their speed has barely changed over the past 25 years. It’s possible that it has snowed less in this part of Antarctica in recent years—that would also cause the glaciers to thin and lose mass, but it’s a not a signal of dynamical imbalance.”

Continued here.

Comments
  1. Timo Soren says:

    it’s a not a signal of dynamical imbalance

    Post it everywhere, maybe someone will process it and understand.

  2. ren says:

    Changes in penguin populations on the Antarctic Peninsula have been linked to several environmental factors, but the potentially devastating impact of volcanic activity has not been considered. Here we use detailed biogeochemical analyses to track past penguin colony change over the last 8,500 years on Ardley Island, home to one of the Antarctic Peninsula’s largest breeding populations of gentoo penguins. The first sustained penguin colony was established on Ardley Island c. 6,700 years ago, pre-dating sub-fossil evidence of Peninsula-wide occupation by c. 1,000 years. The colony experienced five population maxima during the Holocene. Overall, we find no consistent relationships with local-regional atmospheric and ocean temperatures or sea-ice conditions, although the colony population maximum, c. 4,000–3,000 years ago, corresponds with regionally elevated temperatures. Instead, at least three of the five phases of penguin colony expansion were abruptly ended by large eruptions from the Deception Island volcano, resulting in near-complete local extinction of the colony, with, on average, 400–800 years required for sustainable recovery.
    https://www.nature.com/articles/ncomms14914

  3. ren says:

    Over the last decade the AP region has largely been described as one
    of the fastest warming regions on Earth, with comparable amplitude to
    the Arctic region. The IPCC (2007) suggested an increase of MAAT
    between 2 and 3 °C for 2080–2099 with respect to the average 1980–
    1999, although this range was later reduced by the latest IPCC assessment
    (IPCC, 2013) to circa 1.8 °C for the entire continent. It should be
    stressed that these recent temperature increments are significantly
    lower than the corresponding temperature increase projected in the
    Arctic by the end of the 21st century estimated at 4.9 °C (IPCC, 2007,
    2013). Most of the research dealing with terrestrial and marine regional
    earth systems and ecosystems has used this warming paradigm as the
    climatic framework. This widely accepted framework can be found in
    many papers published since the early 2000s that take into account
    the long-term trend recorded during the second half of the 20th century.
    However, this trend masks the internal short-term climate variability
    of a highly sensitive climatic region where feed-back processes (e.g. sea
    ice and snow cover extent and duration) strongly influence the regional
    climatic trends and their impacts on the cryosphere and on ecosystems.
    The largely referred warming at Faraday/Vernadsky station since the
    late 1950s constitutes the largest increase recorded within the AP region,
    and to a certain extent, is not representative of the whole AP.
    The SW corner of the AP is the area which has warmed most over the
    last decades, with an increase of 1.6 °C since the 1976–1985 decade
    and of 0.7–1.1 °C since the 1986–1995 decade. For the rest of stations,
    the MAATs during the 1960–70s were considerably lower, within the
    range of 0.5–1.2 °C colder than during the 2006–2015 decade and the
    warmest temperatures were recorded during the 1996–2005 decade.
    The shift to a cooling trend initiated around 1998/1999 has implied a
    decrease in temperatures between the decades 1996–2005 and 2006–
    2015 by 0.5–0.9 °C in most of the AP region (at Orcadas station, the
    cooling was of only 0.2 °C), with the exception in the SW sector of the
    AP. Here, despite the rate of increase has significantly decreased during
    the most recent decade 2006–2015, the MAATs have still been 0.1–
    0.2 °C higher than those of the previous decade.
    The recent cooling has been seasonally dependent, being particularly
    pronounced in the N-NE tip of the AP and the SSI during the autumn
    and winter seasons. By contrast, no clear changes in the MSAT variability
    have been recorded in the SW of the AP. These changes (and relative
    stability) of the MSATs are strongly influenced by the variations on the
    extent and duration of sea ice, which is known to be partially controlled
    by the prevailing SAM-ENSO conditions in the AP region. However, besides
    the regional influence of the large-scale modes of climate variability,
    local factors, such as topography, would also play a key role. The
    lower MAATs detected in the region during the last decade may explain
    some of the observed environmental changes, including increase in the
    extent of sea ice, positive mass-balance of peripheral glaciers and thinning
    of the active layer of permafrost.
    We acknowledge that, similarly to other regions of the world, it is
    rather difficult to disentangle climate change trends from decadal and
    inter-annual variability, particularly when both natural (e.g. ENSO and
    SAM) as well as anthropogenic (greenhouse gas emissions and ozone
    depletion) factors play significant roles in the evolution of the climate
    of Antarctica in general and the AP in particular. In this regard, it will
    be particularly important to evaluate the regional impact of the recent
    major El-Niño episode unfolding between 2015 and 2016, in particular
    to see if this event will induce widespread warming in the entire AP region,
    as happened following the 1982–83 and 1997–98 El Niño events
    (Fig. 4).
    The recent cooling has not still impacted the large AP ice masses,
    such as ice sheets and outlet glaciers and ice shelves, but smaller ice
    masses in the northern AP and surrounding islands are already showing
    signs of this warming trend. Nevertheless, some initial impacts on
    cryosphere have been observed already. Marine and land-terminating
    glaciers on the northern AP experienced a decelerated recession for
    the 2000s. Peripheral glaciers in the northern AP islands have shown a
    shift from surface mass losses to surface mass gains, highlighting that
    ice on the AP is now particularly susceptible to rapid increases in melting
    and loss in response to small mean temperature oscillations. Finally,
    in recent years, the cooling trend recorded since the mid-2000s and the
    220 M. Oliva et al. / Science of the Total Environment 580 (2017) 210–223
    related long-lasting snow cover have clearly affected the soil thermal regime.
    The reduction of the active layer thickness has appeared in some
    regions of the SSI and N-NE Antarctic Peninsula.
    Future research will unveil if the recent cooling trend observed in
    significant parts of the AP is part of the natural climatic variability in
    the region, or shows a turning point in the long-term warming trend observed
    during the second half of the 20th century.
    https://www.researchgate.net/publication/311631630_Recent_regional_climate_cooling_on_the_Antarctic_Peninsula_and_associated_impacts_on_the_cryosphere#pf6

  4. oldbrew says:

    ‘Future research will unveil if the recent cooling trend observed in significant parts of the AP is part of the natural climatic variability in the region, or shows a turning point in the long-term warming trend observed during the second half of the 20th century.’

    Indeed. And ‘the recent cooling trend observed in significant parts of the AP’ is not something climate alarmists want people to know about.

    ‘natural climatic variability’ can also work both ways – warming or cooling.

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