Poolkappen, IJsbergen en Gletsjers #4

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Largest glacier in Greenland is growing for third year in a row, thickening

Jakobshavn Glacier in western Greenland, best known for being world's fastest-moving glacier, is growing for the third year in a row. By the third year, thickening is occurring across an increasingly wide area.

The glacier has spent decades in retreat until scientists observed an unexpected advance between 2016 and 2017. In addition to growing toward the ocean, the glacier was found to be slowing and thickening.

Data collected in March 2019 confirm that the glacier has grown for the third year in a row, and scientists attribute the change to cool ocean waters, Kathryn Hansen of NASA's Earth Observatory reports.

"The third straight year of thickening of Greenland’s biggest glacier supports our conclusion that the ocean is the culprit," said Josh Willis, an ocean scientist at NASA’s Jet Propulsion Laboratory and principal investigator of the Oceans Melting Greenland (OMG) mission.

The maps below show how the glacier’s height changed between March 2016 and 2017 (top); March 2017 and 2018 (middle); and March 2018 and 2019 (bottom). The elevation data come from a radar altimeter that has been flown on research airplanes each spring as part of OMG. Blue areas represent where the glacier’s height has increased, in some areas by as much as 30 m (98 feet) per year.



The change is particularly striking at the glacier’s front (solid blue area on the left) between 2016 and 2017. That’s when the glacier advanced the most, replacing open water and sea ice with towering glacial ice. The glacier has not advanced as much since then, but it continues to slow and thicken.

Willis and colleagues think the glacier is reacting to a shift in a climate pattern called the North Atlantic Oscillation, which has brought cold water northward along Greenland’s west coast. Measurements of the temperatures collected by the OMG team show that the cold water has persisted.

The team will go back to Greenland in August.

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Large calving event imminent on Brunt Ice Shelf
Two large cracks, Chasm 1 and the ‘Halloween Crack’, are growing on the Brunt Ice Shelf in Antarctica and when they meet, a large iceberg around 3 times the size of Leeds (1,594 km2) will break off.

We use satellite images to measure the growth of both cracks on the Brunt Ice Shelf, along with tracking visible features on the ice shelf surface to measure the ice speed.

Chasm1, located on the West side of the Brunt Ice Shelf, lay dormant for 35 years, but in 2012 it showed signs of movement before starting to propagate across the ice shelf. In 2014 the crack began to grow even more rapidly, and is now over 55 km long! There is now only a 5 km bridge of ice between the tip of Chasm 1 and the McDonald Ice Rumples. When it breaks through, a new iceberg will calve.

A second fracture on the Eastern side of the Brunt Ice Shelf, named the ‘Halloween Crack’ because of its discovery on the 31st October 2016, is growing inland away from the McDonald Ice Rumples. Although the Halloween Crack is more recent, it is now also over 60 km long. Watch the drone footage below to fly along the length of the crack!

Breaking Brunt Ice Shelf

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UniversityLeeds twitterde op dinsdag 25-06-2019 om 11:30:00 An iceberg larger than Greater London is about to break off from the Brunt Ice Shelf, Antarctica. Our @CPOM_news scientists are keeping a close eye on the cracks with colleagues from @ESA_EO and @BAS_News.See the latest data as it happens: https://t.co/C09R2YE8ua https://t.co/flllM7Ptsr reageer retweet

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UniversityLeeds twitterde op dinsdag 25-06-2019 om 11:55:01 We could be just weeks or days away from the biggest iceberg calving event ever observed on the Brunt Ice Shelf. Dr Anna Hogg from @CPOM_news has a "live page" where you can see the latest @CopernicusEU satellite data as it comes in: https://t.co/C09R2YE8ua https://t.co/AsoB52SC0O reageer retweet

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SSW event above South Pole to go down as the strongest on record

Very rare Sudden Stratospheric Warming (SSW) event continues unfolding above the South Pole.

This SSW could go down in history as the strongest warming event on record, NIWA said, adding there is increased risk for southerlies in New Zealand into October.

SSW events are rare in the southern hemisphere, with only two in New Zealand in recorded times - one in September 2002 and the other in September 2010

The Australian Bureau of Meteorology is also predicting it as the strongest Antarctic warming on record, likely to exceed the previous record of September 2002 when New Zealand experienced its coldest October in 20 years.



Below-average temperatures covered much of the country in 2002, resulting in frequent ground frosts.

In 2010 SSW event – which is classed as a minor event – a number of rainfall records were broken with well below normal sunshine and very cold temperatures in parts of the South Island.

"Although we have seen plenty of weak or moderate variations in the polar vortex over the past 60 years, the only other true sudden stratospheric warming event in the Southern Hemisphere was in September 2002," BOM meteorologists said.

"Impacts from this stratospheric warming are likely to reach Earth’s surface in the next month and possibly extend through to January. Apart from warming the Antarctic region, the most notable effect will be a shift of the Southern Ocean westerly winds towards the Equator.

"For regions directly in the path of the strongest westerlies, which includes western Tasmania, New Zealand’s South Island, and Patagonia in South America, this generally results in more storminess and rainfall, and colder temperatures. But for subtropical Australia, which largely sits north of the main belt of westerlies, the shift results in reduced rainfall, clearer skies, and warmer temperatures.

"Past stratospheric warming events and associated wind changes have had their strongest effects in NSW and southern Queensland, where springtime temperatures increased, rainfall decreased and heatwaves and fire risk rose."

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NiwaWeather twitterde op dinsdag 10-09-2019 om 02:57:51 Sudden Stratospheric Warming update?? It happened and continues to unfold.? It set high temperature records in the stratosphere.? It could go down as the strongest warming event on record.? Increased risk for southerlies in New Zealand into October ? https://t.co/mEZcRyV74u reageer retweet

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IJsberg ter grootte van Malta losgebroken van Antarctica

Aan de westkant van Antarctica is eerder deze maand een enorme ijsberg losgebroken, zo blijkt uit satellietbeelden. De bevroren massa heeft een oppervlak van 300 vierkante kilometer en is daarmee ongeveer even groot als Malta.

Op satellietbeelden van het European Space Agency (ESA) was eerder deze maand te zien hoe een enorme scheur was ontstaan in de Pine Island-gletsjer. Een paar dagen later brak de ijsberg af, waarna het gevaarte in meerdere stukken brak.

'Prachtig en angstaanjagend'
"Waar we naar kijken is zowel prachtig als angstaanjagend", zegt Mark Drinkwater van het ESA tegen CNN. Volgens hem is het afbreken van het enorme stuk ijs een direct gevolg van klimaatverandering.

Het komt op Antarctica vaker voor dat ijsbergen losbreken, maar volgens Drinkwater gebeurt het tegenwoordig veel frequenter dan voorheen. Bovendien zou de gletsjer door de stijgende watertemperatuur en een gebrek aan sneeuw niet in staat zijn zichzelf te repareren. Recentelijk werd op Antarctica de hoogste temperatuur ooit gemeten: 18 graden Celsius.

De Pine Island-gletsjer is een van de grootste gletsjers op Antarctica. Samen met de Thwaites-gletsjer vormt die een ijsmassa die bij smelting voor een stijging van 1,2 meter van de zeespiegel zou zorgen. "Dat zou een enorme economische en maatschappelijke impact hebben."

De afgelopen jaren zijn van de Pine Island-gletsjer vaker grote ijsbergen losgebroken. In 2013 brak een stuk ijsmassa af met een oppervlak ter grootte van Singapore.