So for the whole history of time, we have three data points over 4 years for ice depth on Mt. Blanc. (climate-skeptic.com)
Either way, the research hints at a basin depth far larger than the 500 m (1,640 ft) minimum ice depth needed for the convection process to occur. (newatlas.com)
But his trip was a few decades ago when the average sea ice depth was 3.1 meters; now it is down to 1.7 meters and models suggest that it will continue thinning and retreating with our global warming. (williamcalvin.com)