In exploring the lakes of the Hudson Bay Lowlands, five researchers have found one of the world's last refuges from global warming has been heating up dramatically since the mid-1990s
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The
Arctic has experienced some of Earth's first and greatest effects of
climate change, but the icy lowlands around Hudson Bay have remained
remarkably resistant to warming—until recently.
A new study reports
that, since the mid-1990s, aquatic ecosystems in one of the Arctic's
last refugia have undergone dramatic climate-driven changes and appear
to have reached an ecological tipping point.
While
local temperatures had remained relatively steady before the last two
decades, they've risen since then at rates that are extremely high even
for the Arctic.
The increase has changed the mix of freshwater organisms
that anchor local food chains in a way never before seen over centuries
of historical record.
(Related: "Summer Arctic Sea Ice Recovers From 2012, But Trend 'Decidedly' Down.")
(Related: "Summer Arctic Sea Ice Recovers From 2012, But Trend 'Decidedly' Down.")
"The
Arctic is often described as Earth's 'canary in the coal mine' because
it's the first area to show change. Shifts also happen very quickly
there," said John Smol, a paleolimnologist at Queen's University in Kingston, Ontario, whose new research on the area was released today.
Smol
added that, although data show Arctic warming dating back to the 1800s,
there were always a few refugia that seemed relatively resistant to
change—including this area around Hudson Bay.
"There
were good reasons for that," he said.
"Hudson Bay is the second largest
inland sea in the world, and it is choked with ice that helped keep the
area cool," he said.
"So it had to pass a kind of tipping point. Only
since the mid-1990s has it warmed up enough that it started losing its
ice."
Hudson Bay has warmed about three degrees Celsius
since the 1990s, and change has accelerated, said Smol.
"We see some
striking ecosystem shifts in these lakes."
Smol pointed to increased stratification in the lake by temperature layers and shifts in algae.
Smol pointed to increased stratification in the lake by temperature layers and shifts in algae.
An aerial view shows the landscape typical of the Hudson Bay Lowlands in Ontario.
A new study of lake sediment core samples by Queen's University researchers shows the area has warmed rapidly in the last 15 years. (Kathleen Ruehland/Queen's University)
Paleoclimate History Written in Mud
While
the area's native peoples maintain traditional knowledge of past
conditions and stress significant recent changes, there isn't any
long-term historical record of climatological data in the region.
But
the evidence for these changes and their unique historical context is
locked in mud on the bottom of local lakes in what Smol calls "natural
archives."
"Lake
sediments slowly accumulate, 24 hours a day and 365 days a year,
layering and preserving an incredible amount of information in the mud,"
Smol said.
"So they are like a paleoclimatological history book if we
learn to pull the information out of them."
Many
organisms left microscopic fossils behind, especially algae.
Since
different species survive under different conditions—like altered water
chemistry or icy flows, compared with more open water—scientists can
work out past conditions by studying such tiny fossils.
Sediment
cores and the ancient algae they contain go back a thousand years in
some cases and show that the Hudson Bay region's lakes experienced very
little biological change over the centuries—until the past few decades.
After the mid-1990s, the aquatic biota in the sediment record show
striking shifts in ecosystems that are very similar to those seen
elsewhere across the Arctic in regions where air temperatures warmed and
time periods of ice-free water increased.
"Essentially,
this region warmed a couple of decades later than most of the rest of
the Arctic, and the lake flora has experienced rapid shifts similar to
previous changes in other lakes," said Konrad Hughen, a researcher at the Woods Hole Oceanographic Institution who was not affiliated with the study.
"One
important observation they make is that the timing of these late
changes coincides with local warming, not regionally increased nitrogen
[nutrient] deposition. So, this supports the previous conclusions about
changes in other lakes around the Arctic that they were caused by
widespread warming and not nutrient changes."
Strange New World
On
the other side of the globe, Antarctic sea ice has expanded so much it
set a record—for the second year in a row.
Back-to-back iciest years
since record keeping began in 1978 have left scientists searching for
explanations—especially because the Southern Ocean waters below have
continued to warm. (Related: "Antarctic Sea Ice Hits Record ... High?")
Physical
changes on tap around Hudson Bay could mirror those seen earlier in the
high Arctic, Smol said, including less lake ice, shallower or dried-up
lakes and ponds, and the loss of productive wet peat lands.
Recent
studies have suggested negative impacts on brook charr and other fish
important to local peoples who must deal with the shifting landscape.
"There
are real changes happening, and now we have paleoclimatological
records," Smol said.
"This was one of the last holdouts in the Arctic, but now I feel we've lost it and we're entering uncharted territory." (Related: "Why Predicting Sea Ice Cover Is So Difficult.")
"This was one of the last holdouts in the Arctic, but now I feel we've lost it and we're entering uncharted territory." (Related: "Why Predicting Sea Ice Cover Is So Difficult.")
The research was published in Proceedings of the Royal Society B.
Links :
Links :
- Wetlands of the Hudson Bay Lowland : an Ontario overview
