At radio-frequencies, measurements of the permittivity of ice are sparse and with unknown or large uncertainty.
Although that might seem easy to check, data for air temperature over the Arctic sea ice is quite sparse, says Gregory Flato, a sea ice scientist at the Canadian Centre for Climate Modelling and Analysis in Victoria.
As Shell learned during their troubled 2012 drilling season, Arctic exploration means dealing with high winds, rough seas, shifting ice, and very sparse infrastructure.
Sparse human populations and an ice-covered ocean have helped to protect Arctic biodiversity from human activity in the past, but similar protection has not occurred on the Atlantic and Pacific coasts.
However, he cautions, the data on ice thickness are too sparse to define a climate trend.
The whole thickness of the tephra-bearing ice layer including brighter sparse part is about 20 cm on average.
Located between Greenland and Russia, Svalbard experienced a near-complete loss of its vegetation during the last ice age and was quite sparse even 10,000 years ago, but today it is home to a thriving plant community.
Sparse but compelling paleoecological data and relict ice- or sand-wedge polygons provide clear evidence for a cold climate and widespread permafrost around the peak of the last glaciation.
The match was played in the imposingly beautiful centre court, although the crowd was sparse as the locals headed for the pizza and ice cream stalls in readiness for the subsequent all-Italian encounter between Fabio Fognini and Andreas Seppi.
Unfortunately, improving the models requires observations, and "Antarctica and the sea ice lanes are some of the most data sparse regions on earth," he says.
