Samcot_annual_report

Annual Report 2016

SAMCoT

Thermodynamic consolidation of ice ridges occurs due

to atmospheric cooling from the surface and due to the

freshening of the water trapped inside the rubble caused

by the rubble melting. The latter process is very slow

when the oceanic heat flux to the ice bottom is small

(<10 W/m

) and develops faster when the rubble drifts

to warm water areas.

WP1 researchers studied the consolidation of ice rubble

in the region of Bjørnøya. The ice drift and water surface

temperature reconstructed from the data from the

spectroradiometer MODIS flown on two NASA spacecraft

(Terra and Aqua) show that sea ice tongues drifted se-

veral times in March 2016 from the North to the region

with water surface temperature around 0 - +1

⁰

C under

the influence of Polar cyclones formed near Bjørnøya.

Oceanic heat flux to the ice bottom, estimated for

these conditions with standard formulae, can reach

CONSOLIDATION OF ICE RUBBLE IN WARM WATER

100 W/m

and higher. Numerical simulations performed

with the original model of thermodynamic consolidation

show that rubble ice with a macro-porosity of 20%

can be completely consolidated in 1-2 months. At the

same time, the rubble draft decreases due to melting.

Therefore drifting ridges are transformed into relatively

large consolidated sea ice features with vertical scales

of several meters which are similar to “bergy bits”.

These ice features create potential risks for

navigation near Bjørnøya. Predictions could be made

using satellite information and ice maps.

WP1 researchers are very excited by these findings,

and hope to further study and analyze the consolidation

of ice rubble in warm waters. One example of such

ice features was spotted near Edgeøya during the RV

Lance expedition in May 2016. WP1 researchers have

discovered that this rubble has been forming by the

accumulation of ice that drifts from the North.

This mass showed a concentration of 20 icebergs per

with an average size of 20*40 m. N. Marchenko

scanned this huge ice rubble field and processed point

clouds from the scans using the RiScan and ArcGIS

programs. In addition, she studied high-resolution

satellite images of the same mass to obtain further

information on the structure and origin of the ice rubble.

She discovered that the rubble mass existed from the

beginning of April to the beginning of July.

On the basis of data obtained from IFREMER and WP1

Ice trackersit was concluded that these ice features

may reach Bjørnøya in two and a half months in cases

when average drift applies. However, when polar

cyclones and strong wind gust are observed, the drift

can be much faster and these ice features or remnants

of them may reach Bjørnøya in a month. Terra satellite

images show that the ice tongues reaching Bjørnøya

were visible every March 2015 – 2017.

Ice rubble observed near Edgeøya during the Lance cruise on 2 May 2016. Vertical wall: 3 m; average elevation above water: 2 m;

width from coastal line: 8 km; stretching in N-S direction along the coast: >20 km.