Mission belge Antarctique 2018

Category: Antarctic climate

How strong are the winds in Antarctica ?

by Hugues Goosse

Antarctica is often referred to as the windiest continent on Earth for several reasons. First, there is not many obstacles at surface like hills, buildings or trees that can slow down the winds. Second, even though large portions of the continent are flat, some regions experience large slopes that can be followed by intense winds. Finally, large temperature contrasts can induce large pressure difference and thus strong winds, at a different scale but in a similar way as in air flows in your house.

The strongest winds, called katabatic winds, occurred in coastal regions. The air in the interior of the continent, where the altitude of the surface is high, is very cold, and thus very dense. This dense air may literally flow down the slope towards the coast because of the gravity, accelerating until it reaches very high velocities.

Those winds can achieve velocities higher than 200 km/h. They are so strong that, even in winter, they can transport all the sea ice floating at the surface of the ocean away from the coast as soon as it is formed, leaving the ocean ice free even though the air temperature is -20°C.

Fortunately for us, katabatic winds very rarely occurs in summer close to the station and at our measurement sites. Nevertheless, the winds can still be very strong, blowing large amount of snow over long distances.

Vidéo taken in 2017 by Jean-Louis Tison of katabatic winds in the Ross Sea

Vidéo taken by Nander Wever during the storm that hit us at Novo station

 

 

 

 

Why Belgium continues to keep an exceptional position in Antarctic research

By Jean-Louis Tison

Our previous blog post has described how the efficiency in the logistics and the expertise of the International Polar Foundation allows carrying out research projects like Mass2Ant.

You have seen that polar research implies strong logistic constrains, in a remote place. Polar research also requires up-to-date scientific equipment in the field and in the laboratories for the analyses as well as manpower from the researchers and technicians involved.

Here, as in many other cases, funding remains the key issue! Belgium does not have a polar institute with specific funding like other European countries (France, Germany, Italy,…) and Belgian scientists must thus find other funding sources.

Thanks to its historical involvement in Antarctica (since the expedition of de Gerlache in the late XIX century), Belgium has always maintained a strong position in Antarctica, and more generally in polar research.

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Do you feel global warming in Antarctica?

by Hugues Goosse

Even if we have 24 hours of light in this season, the temperature is higher at noon when the Sun is higher above the horizon than at midnight. Close to our camp, at the location of our weather stations, the difference between day and night is generally about 5 to 10 degrees.

Consequently, the ‘night’ can still be cold with temperatures well below -10°C. Nevertheless, as the Sun rises again and hits our individual orange tents, we are quickly boiling within our sleeping bags!

Figure from Quentin Dalaiden based on the dataset of Nicolas and Bromwich (2014)

In cases of a cold events like this one, you probably have heard people questioning global warming or calling for a temperature rise that would prevent us from such cold conditions. We know that having particularly cold or warm days is normal. It depends on weather conditions and is generally not at all related to climate change.

Nevertheless, a succession of warm events or a warming tendency can be the signature of the local impact of global changes. This is clearly the case in the Arctic where the large surface temperature increase and the melting of sea ice have been attributed to human-induced climate change without ambiguity.

The situation is different in Antarctica and the Southern Ocean. Since 1979 (i.e. since the beginning of reliable estimates based on satellite measurements), there were no clear trend in sea ice extent in the Southern Ocean. The Antarctic Peninsula and West Antarctica have warmed a lot since the 1950’s but not East Antarctica.

Climate dynamics implies that the current warming due to human activities should be smaller in Antarctica than in the Arctic1. We also expect large natural climate variations in Antarctica. The signal related to global warming has thus not yet clearly emerged from the range of natural fluctuations.

In other words, we do not know yet precisely which part of the observed changes in Antarctica are caused by human activities and which ones are due to natural variations of the system, calling for more studies in this important region for our planet.

1 The Southern Ocean includes a huge amount of cold waters. A lot of energy is required to warm it up. This energy is taken from the atmosphere, preventing a large warming of the air in contact with the ocean and more generally of the climate at high southern latitudes. Additionally, because of the dynamics of the Southern Ocean, the surface water that is warmed up by exchanges with the atmosphere is continuously transported to subsurface and replaced by colder water, amplifying the role of thermostat of the Southern Ocean.

How much snow is falling in Antarctica?

By Eric.Keenan

 Antarctica is the coldest continent on Earth, therefore it comes as no surprise that most precipitation falls as snow and that the continent is blanketed in glaciers up to 4.5 kilometers thick. In fact, so much snow and ice is trapped in Antarctica that if it were to all melt, global sea-level would rise about 60meters.

For the ice sheet to maintain its equilibrium, and not contribute to sea-level rise, snowfall must balance processes that remove snow and ice from Antarctica, including iceberg calving, surface sublimation, and runoff from meltwater.

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Why are we interested in the mass balance of Antarctica, and what is it exactly?

By Sarah Wauthy

The ice sheet mass balance (MB) measures the changes in the total mass of the ice sheet. It is the difference between the ice accumulation due to snow fall and ice mass losses mainly due to local melting (and sublimation) or ice transport toward the ocean, where ice ultimately melts too.

More precisely, the surface mass balance is computed as the difference between surface mass balance (SMB), and solid ice discharge (D, i.e the formation of icebergs) and ice shelf bottom melting (M) (the ice sheet part that starts to float on the ocean – by virtue of Archimedes’ principle – in the coastal regions of Antarctica), i.e. MB = SMB – D – M.

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Why studying Antarctica ?

by Hugues Goosse

Antarctica and the Southern Ocean are among the most remote places on Earth. Because of their beauty and mysteries, they have since their discovery received a lot of attention from explorers and scientists as well as from the general public.

Scientific research in Antarctica was initially motivated by improving our knowledge of the polar regions and by the protection of this pristine environment as a heritage for Humanity. However, it was quickly recognized that the high latitudes of the Southern Hemisphere have a global impact on the Earth System.

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