Evidence for Little Ice Age in Antarctica

The actual title of the article is: Century-old seal pelts reveal changes in Ross Sea ecosystem.  ~ctm

From the UC Santa Cruz Newscenter

 

Scientists found valuable samples for comparison to modern Weddell seals in the huts of Antarctic explorers Ernest Shackleton and Robert Falcon Scott

August 29, 2017

By Tim Stephens

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Cape Evans Hut served as base camp to the ill-fated Terra Nova expedition to the South Pole led by Captain Robert Falcon Scott in 1910-1913. Early Antarctic explorers hunted Weddell seals to use their blubber and meat for food and fuel and to feed their sled dogs. (Photo by Daniel P. Costa)

 

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Inside the Cape Evans Hut is a pile of  Weddell seal pelts from a hundred years ago. Researchers compared samples from these pelts and from modern Weddell seals to see if the ecology of the species has changed in the last century. (Photo by Luis Huckstadt)

 

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A Weddell seal swimming in McMurdo Sound, Ross Sea, Antarctica. (Photo by Daniel P. Costa)

 

When scientists at McMurdo Station in Antarctica have time off from their field work, they often pay a visit to three nearby wooden huts built in the early 1900s by Antarctic explorers Ernest Shackleton and Robert Falcon Scott. That’s what UC Santa Cruz biologists Daniel Costa and Luis Huckstadt were doing on a day off from studying Weddell seals when they realized that a pile of frozen pelts in one of the huts represented samples of Weddell seal tissue from more than 100 years ago, at the very start of human activities in Antarctica.

By using sophisticated isotope analysis to compare samples from modern and century-old seals, the researchers were able to investigate an urgent question about human impacts on the Antarctic ecosystem: Is the targeting of Antarctic toothfish by a small fishing fleet operating in the Ross Sea changing the structure of the ecosystem and altering the diets of Weddell seals?

“People have hypothesized that the toothfish are being depleted and that, as a consequence, the Weddell seal has shifted its diet to Antarctic silverfish,” said Huckstadt, a postdoctoral researcher in Costa’s lab at UC Santa Cruz. “We’d been talking about this issue and realized we had the samples right there to test it.”

Their findings, published August 30 in Proceedings of the Royal Society B, indicate that the seals’ diets probably have not changed much over the past hundred years. But the results did reveal evidence of significant change in the phytoplankton community, the microscopic marine algae at the base of the entire food web in the Ross Sea. They attributed this change to a climatic shift that began with the end of a global cooling period known as the Little Ice Age, which lasted from about 1500 to 1900.

With permission from the Antarctic Heritage Trust, Huckstadt and Costa, a professor of ecology and evolutionary biology, collected samples of fur from 34 pelts for comparison with samples from modern-day seals. To analyze them, they teamed up with two colleagues at UC Santa Cruz who are experts in isotope analysis: professor of ocean sciences Matthew McCarthy and professor of Earth and planetary sciences Paul Koch, both coauthors of the paper.

“I first visited the historic huts in 1978 on my first trip to the Antarctic,” Costa said. “I was amazed that the huts were left in the same condition as the day the explorers left 100 years ago. I saw seal pelts, penguin carcasses, and remains of sled dogs literally frozen in time. I always wondered if there was something we could do with this material. These relatively new isotope analyses provided us a way of using those frozen artifacts as a snapshot of the past.”

Stable isotopes of carbon and nitrogen are widely used as tracers of ecological processes. As top predators in the Antarctic ecosystem, Weddell seals incorporate into their tissues isotopic tracers that have passed up through the entire food chain, carrying evidence of the structure of the ecosystem and of the position or “trophic level” of the seals within the system.

The researchers found that the historical “isotopic niche” of Weddell seals (as indicated by the variability of the carbon and nitrogen isotopes) was over five times larger than the modern niche. This could reflect a more highly specialized diet in modern Weddell seals, but this seems unlikely given the diversity of their prey today.

Furthermore, an analysis of nitrogen isotopes in specific amino acids showed that the trophic level of Weddell seals is unchanged, suggesting they are still eating the same kinds of fish as they did historically. Currently, Antarctic toothfish appears to make up less than 10 percent of the diet of Weddell seals, and the findings suggest this was also the case 100 years ago.

Changes in the sources of nitrogen and the composition of the phytoplankton community are more likely to account for the differences seen in the isotope data, Huckstadt said. “It looks more like a shift at the base of the food web, probably related to the transition from the Little Ice Age to current conditions, causing changes in the phytoplankton community,” he said.

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28 thoughts on “Evidence for Little Ice Age in Antarctica

  1. from the article: “… phytoplankton community, the microscopic marine algae at the base of the entire food web in the Ross Sea”

    since phytoplankton consume Carbon dioxide, Carbon Dioxide is the “base of the entire food web”

    • The food chain normally refers to living creatures which eat each other, not basic chemical elements.

      This study seems to make a lot of guesses and value judgements and inferring rather a lot from very little actual observed results. Typical climatology.

      • All those ‘living creatures’ (carbon based life forms) that consume each other are moving carbon through the food chain. But what is the origin of that carbon?

        There is no food chain without Carbon Dioxide.

      • There is extreme microscopic life that lives off of CH4. I agree no CO2, end of most life on planet.

      • Thank you William Astley –

        “There is extreme microscopic life that lives off of CH4 …”

        [ Methanotrophs (sometimes called methanophiles) are prokaryotes that metabolize methane as their only source of carbon and energy. They can grow aerobically or anaerobically and require single-carbon compounds to survive.

        They have also been used to produce animal feed from natural gas]

        I understand I need to refine the absoluteness of my assertion that all organic carbon comes from CO2. I aim to remain concise, but accuracy is paramount.

      • Stable isotope analysis relies on several isotopes of different elements besides C-12 and C-13. They look at N and O stable isotopes as well. The article simply finds that modern conditions are warmer. There’s no attribution to that except that the LIA ended about the time Shackleton and Scot were having their adventures. The use of 1900 as an approximate end of the LIA is an alternative data to ca. 1850 which is also sometimes used. So, the conclusion of the article is that humans are NOT at fault for “changes” – nonexistent changes in the ecology of the Weddell seal – claimed by some authors.

    • Some however date its end later in the 19th century. But in any case, it wasn’t like throwing a switch. It takes time for a phytoplankton community to adjust to on average warmer water. Also, the LIA didn’t end at exactly the same time everywhere. It well could have been delayed in Antarctica by thermal inertia and other causes.

      The Current Warm Period consists of warming cycles in the late 19th century, early 20th century and late 20th century, with cooling cycles in between. A century ago would have been at the end of the late 19th to early 20th century cooling.

      We are currently in the early 21st century cooling cycle, although the Super El Nino of 2015-16 has disguised that fact.

    • Tom Halla

      Was 1900 still Little Ice Age? Most sources I have seen date the end at 1835-1860.

      The earth’s climate is cyclical. Or more accurately, the earth’s global average temperatures follow a series of cyclic long-term cycles of about 900-1000 years, with a short cycle of 60-70 years superimposed on that longer cycle. To those two cycles, each year’s actual temperatures are somewhat random, “bouncing” irregularly about the general average for that day-of-year.

      Compare your question to: “When does it stop warming up during spring? I thought Spring started March 22 with the equinox.” The technical, “season” of spring is defined as March 20-21-22 (depending on the year) but clearly the average northern hemisphere temperatures are warmer on March 2 than March 22, but the average temperatures continue warming up until mid-August!

      The global average temperatures were generally lowest back in 1650 – but even “that” was not a specific, clear-cut, absolute date that anyone recognized at the time. 1650 was, instead, the middle of the gradually-changing lowest part of the temperature cycle that really lasted for about 150 years across “a broad shallow minimum period of generally lowest-ever temperatures centered on 1650.”

      We DON’T know if we are at the maximum of the Modern Warming Period (inconveniently the same abbreviation as the Medieval Warming Period and Minoan Warming Period) right now (2000-2020 period). Most likely, we are entering a short cooler period between 60-70 year higher average temperatures, then will slip lower in the Modern Ice Age – whose centerpoint we don’t know yet eitehr! So, if we don not know the end of the rise in temperatures coming out of the Little Ice Age, when did we stop warming from the Little Ice Age?

      We don’t know. One “approximation” is to assume this is a peak, and break off the LIA halfway back between the lowest point (declared to be 1650) and today. But we did NOT stop warming at 1850. In fact, 1850 wouold be the point of MAXIMUM warming rate between the lowest point of the LIA and today’s (possible) MWP peak!

      By the way, that we do not know the reason for the 60-70 year short cycle, nor the 900-1000 year long cycle does not mean they do not exist. Merely that we do not know the reason why they DO exist.

      • “but clearly the average northern hemisphere temperatures are warmer on March 2 than March 22”?
        Is it not the other way? Warmer on March 22 than on March 2.

      • The MWP problem is why I follow the convention of Current WP rather than Modern.

        I also call the centennial-scale trend secular and decennial-scale, trends cycles (pro- and counter- secular trend). But even the secular trends, such as the MWP and LIA, are subsumed under the long-term, millennial-scale trend, which has been cooling for at least 3000 years, since the Minoan WP, but probably 5000 years, since the end of the Holocene Climatic Optimum.

      • I hadn’t seen that clip, but it agrees with my understanding of the basic history. The other major source I was relying on was the recent Chinese study, which is fairly close to European records/proxies.

      • Ice ages don’t have neat terminations and there are various “end dates” offered. Many geologists (Mary Hill for instance) use 1900 as a termination. RACook gives one method. Another is to employ the earliest data when the mean temperature approximates some base period. Curiously, many temperature cycles on this planet develop slowly and end abruptly. That would imply that a “hockey stick” at the actual terminations of the LIA might be predictable from “natural” causes. Thanks to the climate “debate” we may never get the data adequately cleaned up to where we can tell if that is so.

  2. This paper from 2011 finds much stronger evidence of the LIA in Antarctica:

    http://www.sciencedirect.com/science/article/pii/S0012821X11002925

    From the Abstract:

    Here we present new data from the Ross Sea, Antarctica, that indicates surface temperatures were ~ 2 °C colder during the LIA, with colder sea surface temperatures in the Southern Ocean and/or increased sea-ice extent, stronger katabatic winds, and decreased snow accumulation. Whilst we find there was large spatial and temporal variability, overall Antarctica was cooler and stormier during the LIA.

  3. I see at least 2 major problems with this study. #1 everyone knows the temperature has been constant since forever until humans started burning oil, hence no little ice age, Mike Mann told me so. #2 – one of the researchers last name is Koch, which means the whole group is in league with oil barons and various other sources of evil, Harry Reid (noted exercise equipment fighter) told me that one.

  4. 1900 was not at the LIA. The LIA was finished by 1840. 1900 corresponds to a cool period during the Gleissberg solar minimum. It is part of the current global warming, that started around 1650, and after ending the LIA, has produced the Modern Climate Optimum or Warm Period we are enjoying.

    The Little Ice Age was a term invented by a newspaper reporter when Françoise Matthes explained to him in the 1940’s the growth of glaciers for the past 4-5,000 years (Neoglacial period). Matthes liked the term and used it when talking to other researchers. It was later restricted to the final colder stage of the Neoglacial when glaciers reached their maximum Holocene extent, when it finally appeared in the scientific literature. The LIA doesn’t have a date definition agreement, but 1900 is really pushing it too much. I use 1250 and 1840 as start and end of the LIA, because the temperature change at those times supposed a clear change from predominant previous conditions. Most authors prefer to restrict it even further to the coldest periods that took place between 1430 and 1825.

  5. I’ve noticed a few studies that reference the Little Ice Age have push the dates for it closer to current. In big round numbers I always thought of LIA as 1450-1850 +/-. This study gives LIA as 1500-1900, pushing it forward about 50 years. I don’t understand the reasoning for this.

    I guess we should be happy that some scientist still believe the LIA was a real event. Even happier that these scientist think it impacted Antarctica.

    • I don’t understand the reasoning for this…..because if you start the temperature record at the peak of the MWP…there’s been no warming at all
      No one knows what caused the LIA….so no one knows when it’s over
      People can claim any end they want, really…we could still be recovering

      The industrial revolution came about around 1850…claiming that’s the end of the LIA…..they can claim all the warming after that was man made

      ….it’s all smoke and mirrors

    • The major problem these days is that too many people seem to believe that ‘global temperature’ (whatever that means) it the driver of the climate. This is to misunderstand what climate is.
      Climate is a local, regional, or zonal effect from a whole heap of influences, and yes air temperature is a major driver, but so too is humidity, chemicals and particulates in the air, oceanic variables, and much more.
      Thus the start and finish of any so called ‘climate event’ will vary depending on local conditions. That is to say there may well be a global climate event but locally what changes, how fast it happens, and how long it affects the region is specific to the locality.
      There really is not a global climate!

    • “I don’t understand the reasoning for this.”

      At least in Greenland the early part of the fifteenth century was warm with little sea-ice.

  6. Can’t be. I was told by none other than William M. Connolley that the LIA was very local (i.e., Europe), very short and Not Very Interesting.

    Certainly couldn’t affect Antarctica, which as you all know, he is an expert in.

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