icebergs

About 8 years ago I took a trip to Newfoundland in June and got to see the icebergs.  Whether they were ice bergs from sea ice or land ice, I don't know.  At the time, I thought they were beautiful and was so excited to be in Newfoundland to see them.  Now, knowing what I know, they cause me anxiety - are they from land the ice of greenland that is being lost at a rate of 286 billion tons per year or from an ice shelf that is still attached by land or from sea ice. And again, from earlier in the course, less ice cover of the land and the oceans, means less ability to reflect back the radiation from the sun and more warming.  

The discussion question with regards to icebergs (or calving) in this section of the course was: How might processes like ocean and atmospheric warming cause mass loss from calving to increase? 

So first let's define calving.  This is where pieces of ice break away from a glacier that ends in a body of water (ie a land glacier extending into the ocean and then breaking away from its base). 

So how will ocean warming contribute.  Ocean warming can melt the underside of the glacier ice shelf (the part of the glacier now on the ocean but still connected to land glacier) weakening it and contributing to calving.  Atmospheric warming can lead to less snow fall and less ability of the normal summer time ice melt to refreeze back to the ice mass.  So with both loss of snow and less ice melt refreezing, there is less accumulation of mass and the glacier starts to spread out more to the edges of the land where they meet the warming oceans.  Atmospheric warming will also allow the lakes that form on the glacier itself more time to absorb more radiation (rather than reflect it back) which further warms them.  When they drain abruptly transferring heat to the interior of the ice sheet, the ice sheet can flow more rapidly to the edges (again meeting the warming oceans and leading to more calving.