GeoLog

imaggeo on mondays

Imaggeo on Mondays: Polar backbone (Arctic Ocean)

Imaggeo on Mondays: Polar backbone (Arctic Ocean)

This image was taken during the Arctic Ocean 2016(AO16) expedition that ventured to the central regions of the Arctic Ocean, including the North Pole. It shows a pressure ridge, or ice ridge, as viewed from onboard the deck of the icebreaker Oden. It was quite striking that the ice ridge resembled an image of a spine – sea ice being a defining characteristic of the broader Arctic environment and backbone to global climate interactions.

An ice ridge is a wall of broken ice that forms when floating ice is deformed by a build up of pressure between adjacent ice floes. Sea ice can drift quite quickly, and is driven by wind and ocean currents. Ridges are typically thicker than the surrounding level sea ice, being built up by ice blocks of different sizes. The submerged portion of the ridge is referred to as the “keel”, and the part above the water surface is called the “sail”. Ridges can be categorized as “first year” or “multi-year” features, with weathering affecting the morphology.

In the Arctic, such ridges have been measured to in excess of 20 m in thickness including keel and sail. As someone who studies plate tectonics, these collisional boundaries between plates of ice reminded me of a downscaled mountain-building setting.

The AO16 expedition ran from August to September 2016 and involved the Swedish icebreaker Oden and the Canadian icebreaker the Louis S. St-Laurent. A wealth of geological, oceanographic, meteorological data was collected. This period appeared to have coincided with the second lowest extent of sea ice coverage on record (tied with 2007), with around 4.14 million square kilometers.

The geological evolution of the Arctic Ocean in the regions closest to the margins of northern Greenland and the Canadian Arctic Islands are some of the most poorly understood. This is largely a function of the oceanic gyre system, which causes the thickest sea ice to build up in these areas making physical access difficult. From a maritime engineering perspective, the ice ridges pose a challenge and risk to icebreaking operations and navigation. Ice ridges may determine the design load for marine and coastal structures such as platforms, ships, pipelines and bridges, and are important for both ice volume estimations and for the strength of pack ice.

By Grace Shephard, geophysicist from the Centre for Earth Evolution and Dynamics (CEED) at the University of Oslo, Norway.

Imaggeo on Mondays: Ice drilling

Ice drilling in Saratov

This week’s Imaggeo on Monday’s post, captured by Maksim Cherviakov, shows students from Saratov National Research University practicing a method to measure lake ice thickness. The students are using an ice auger to manually burrow through the ice. Afterwards, the ice depth is recorded using a tape measure.

“We measure ice thickness every year on the lakes located in the floodplain of the Volga river near Saratov. There are many number of ways to measure the thickness of ice but we use the easiest method. Students also measure air temperature, snow cover and structure of ice. The obtained data can give us information about the dynamics of changes in characteristics of lakes”, says Maksim

When is ice safe to stand on?

Many countries experience cold enough weather for frozen lakes and rivers to be used for recreational and professional activities. It is therefore essential to know the ice thickness and the associated weight limit restrictions. The US State of Minnesota, which experiences average winter temperatures of -9 to -16 degrees Celsius, published this guide (shown below) for people wanting to use its frozen waters. Ice must be at least 8-12 inches (20-30 cm) thick for cars to safely drive on.

Ice thickness guidelines

General ice thickness guidelines. Credit: Minnesota Department of Natural Resources.

Regular analysis of ice thickness, using manual methods like the one shown above or using more automated methods, can help avoid accidents. The video below shows what can happen when isn’t checked. Fortunately, in this instance, no injuries occurred. The Minnesota Department of Natural Resources recommend that vehicles should be parked at least 150 metres apart and moved every two hours to prevent sinking.

 

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

 

Follow

Get every new post on this blog delivered to your Inbox.

Join other followers: