Unique view into the new Arctic

Date:
October 13, 2020
Source:
Leibniz Institute for Tropospheric Research (TROPOS)
Summary:
With the return of the Polarstern, the largest Arctic expedition
of all times has come to a successful end. For more than a year,
the German research icebreaker traveled in 5 cruise legs with more
than 400 people from 20 countries to investigate the epicenter of
climate change more precisely than ever before.



FULL STORY ==========================================================================
With the return of the Polarstern, the largest Arctic expedition of
all times has come to a successful end. For more than a year, the
German research icebreaker travelled in 5 cruise legs with more than
400 people from 20 countries to investigate the epicentre of climate
change more precisely than ever before. At the end of the expedition,
which cost around 140 million euros, the Alfred Wegener Institute,
Helmholtz Centre for Polar and Marine Research (AWI), came to a positive conclusion: despite all the unforeseeable difficulties, it had succeeded
in advancing knowledge about the Earth's climate system and its changes
by a decisive step.


==========================================================================
From Leipzig's point of view, the complex project was also successful:
all 7 participants from the Leibniz Institute for Tropospheric Research (TROPOS) and the Leipzig University are back in good health and with
valuable climate data.

Two measurement programmes that are central to research into the Arctic atmosphere were able to be carried out in full despite weather extremes
and corona: A multi-wavelength lidar scanned the air layers above
Polarstern during the entire expedition. In 369 days, 640 million laser
pulses went into the sky and 112 gigabytes of data were collected. In
July, the MOSAiC atmosphere team was able to measure the lowest air layer
above the melting ice floe with a captive balloon. Within a tight time
window, 33 balloon ascents were achieved, during which a total of 31725
metres of rope were unwound and rewound. The balloon measurements by
TROPOS and Leipzig University are particularly important for understanding
the polar atmosphere during the melting phase, because the measurements originally planned in parallel with aircraft from Spitsbergen had to be postponed until autumn due to the corona pandemic.

"We are pleased that the ambitious plans have essentially been realised
despite all the difficulties. A highlight are definitely the insights into
the troposphere at the North Pole during the winter with our lidar. Nobody
has ever been able to observe it so far north during the polar night off MOSAiC," says Prof. Andreas Macke, Director of TROPOS. The evaluation
of the data is still in full swing, but there are indications that the
same applies to the atmosphere as to the ice on the ground: "There are
many indications that the atmosphere of the Arctic has already changed significantly. We have seen more smoke than expected. The huge forest
fires are apparently affecting the polar regions.

Even these once pristine areas seem to have reached the
'Pyrocene'. However, it will take months before concrete results are
available, during which the data will have to be examined, analysed and discussed before they can finally be published. "The fact that we have
measured both the atmosphere and the energy balance on the ground over
a complete Arctic year will contribute greatly to our understanding of
Arctic warming," adds Macke.

At the moment, the joy that people and technology have survived the
strains well outweighs. Also at Dr. Ronny Engelmann, scientist and
laser expert from TROPOS, who is responsible for the remote sensing measurements within the OCEANET project on Polarstern: "It was fascinating
to experience the Arctic in winter and to be allowed to be in a region
where only a few people have been before at this time of year. As a
scientist, I am glad that, thanks to good care by my colleagues, our
equipment has been able to last for a year and has also survived the
extreme cold of the polar night with temperatures down to -40 degrees
Celsius without any failures. The experiences of the last ten years,
during which our OCEANET container has been on board of Polarstern,
have been a great help. Without stable technology, we would never have
known what dust layers had moved across the Arctic," physicist Engelmann
looks back. The lidar was in operation from 28 September 2019 to 02
October 2020 without any significant failures. This was ensured by Dr
Ronny Engelmann, Hannes Griesche, Martin Radenz, Julian Hofer and Dr
Dietrich Althausen, some of whom spent up to four months on the five
sections of the cruise. Even though the remote sensing instruments run
mostly automatically, they need regular maintenance: the flash lamps that
emit the laser pulses had to be changed five times, for example, or 60
litres of liquid nitrogen had to be replaced each time the microwave
radiometer was calibrated. Together with other instruments such as
radiation meters, cloud camera, rain gauge and photometer on the OCEANET measuring container from TROPOS, a total of over one and a half terabytes
of data were collected and around 60,000 kWh of electricity was consumed.

While the remote sensing instruments on the foredeck of Polarstern
could practically run the entire expedition, the teams on the ice had
only a short time window each, which had to be used as effectively as
possible. The balloon team from TROPOS and Leipzig University was able
to work on the ice for a total of 37 days. Thanks to support from other
teams, 33 balloon ascents were achieved, in which the BELUGA tethered
balloon, which was the size of a bus, could measure aerosol particles, radiation and meteorological parameters up to a height of 1500 metres
above the ice. To fill the balloon several times, 474 cubic metres of
helium were consumed and holes up to 6 metres deep had to be drilled into
the thawing ice for the ice anchors. "Our time on the ice was short but intense. The many melt ponds and frequent polar bear visits demanded
a lot of improvisation. Because of the support from the whole MOSAiC
team we were able to master difficult situations. This made our balloon measurements a big team effort from a great team that I will remember
for a long time to come," said Christian Pilz of TROPOS. The vertical
profiles that Pilz recorded together with the radiation measurements
of his colleague Michael Lonardi from Leipzig University will provide
important insights into the lower atmosphere of the summer Arctic. For
example, the team was able to register temperatures of 14 degrees Celsius
at an altitude of 300 metres, although the temperature on the ground
was only just above freezing point. Without such on-site measurements,
it would not be possible to estimate the influence of the air layers on
the ground on thawing sea ice.

Originally it was planned to study the near-ground atmosphere above the
MOSAiC ice floe by tethered balloon and the higher layers by aeroplane
in early summer. However, due to the corona pandemic, flights via
Spitsbergen were not possible at that time. Supply and personnel exchange
had to be organised with research vessels from Germany and the aircraft campaign had to be postponed until September. "The measurements with
the Leipzig tethered balloon are therefore important in-situ aerosol measurements at MOSAiC in this layer of air, which is very important
for the climate in the Arctic," emphasises Andreas Macke from TROPOS,
"As an atmospheric researcher, I am particularly pleased that the balloon experiment was successful for the second time after 2017 and provided
very valuable data." In September 2020, the German research aircraft
Polar 5 and Polar 6 of the AWI were the first foreign aircraft to take
off from the airport Longyearbyen for several measurement flights from Spitsbergen to the central Arctic to study the atmosphere in the context
of MOSAiC since the corona lockdown: "With the extensive measurements
on radiation and particles, we want to find out how clouds in the Arctic
affect warming on the ground. In recent years, the Arctic has warmed up
more than any other region on earth. The feedback mechanisms involved
are very complex and not yet sufficiently understood. This knowledge is essential, however, if climate models are to be able to estimate how
quickly the climate there will change, even for the region around the
North Pole," explains Prof. Manfred Wendisch from the Leipzig University,
who is also the spokesman for the Collaborative Research Centre "Arctic
Climate Change" of the German Research Foundation (DFG). The network
includes the universities in Bremen, Cologne and Leipzig as well as the
AWI in Bremerhaven and the TROPOS in Leipzig. The aim of the research
network is to observe the dramatic climate change in the Arctic using
various methods in order to improve the reliability of models and enable
more accurate predictions of further warming in the Arctic. The MOSAiC expedition will make a significant contribution to this and will be
intensively evaluated by the alliance partners in the coming months.

"I'm very pleased with how the MOSAiC expedition progressed, and what a complete success it has been. Through the expedition, we can provide the climate data and observations that humanity so urgently needs in order to
make fundamental and pressing political decisions on climate protection,"
said Prof Markus Rex, Expedition Leader and head of the MOSAiC project,
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
(AWI). "We've seen how the Arctic ice is dying. In the summer, even at
the North Pole, it was characterised by extensive melting and erosion. If
we don't make immediate and sweeping efforts to combat climate warming,
we'll soon see ice-free Arctic summers, which will have incalculable repercussions for our own weather and climate. Though today the Central
Arctic remains a fascinating, frozen landscape in winter, the ice is
only half as thick as it was 40 years ago, and the winter temperatures
we encountered were nearly always ten degrees warmer than what Fridtjof
Nansen experienced on his ground-breaking Arctic expedition over 125
years ago." On 20 September 2019 Polarstern departed from the Norwegian
port of Tromso/, bound for the Central Arctic, the epicentre of climate
change. Once there, the ship allowed itself to become trapped in the ice,
and began a one-year-long drift across the North Pole, completely at the
mercy of natural forces -- the route and speed were solely determined by
the ice drift, powered by wind and currents. Over the five cruise legs
of the expedition, a total of 442 researchers, Polarstern crewmembers,
young investigators, teachers and members of the press took part. Seven
ships, several aircraft and more than 80 institutions from 20 countries
were involved. The researchers, who hailed from 37 countries, had a
common goal: to investigate complex interactions in the climate system
between the atmosphere, ice and ocean, so as to better represent them
in climate models. They also explored life in the Central Arctic for an
entire year. Now they have returned home with a wealth of impressions
from the rapidly transforming Arctic, and with an unparalleled treasure
trove of data, which an entire generation of climate researchers will
focus on analysing.

From Leipzig's perspective, the next major measurement campaign in
the Arctic will be the "HALO (AC)" mission with the German research
aircraft HALO and Polar 6 in spring 2022. The tethered balloon BELUGA,
on the other hand, will already return to the Arctic skies in late summer
2021 -- if pandemic conditions permit.


========================================================================== Story Source: Materials provided by Leibniz_Institute_for_Tropospheric_Research_(TROPOS).

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Hannes J. Griesche, Patric Seifert, Albert Ansmann, Holger Baars,
Carola
Barrientos Velasco, Johannes Bu"hl, Ronny Engelmann, Martin Radenz,
Yin Zhenping, Andreas Macke. Application of the shipborne remote
sensing supersite OCEANET for profiling of Arctic aerosols and
clouds during Polarstern cruise PS106. Atmospheric Measurement
Techniques, 2020; 13 (10): 5335 DOI: 10.5194/amt-13-5335-2020 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201013105813.htm

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