Overlapping definitions: a general issue

[pbuttigieg]

With the multi-source nature of the GCW resources, it's natural to have definitions which mostly agree, but diverge on one or two key differentia.

Ablation was an example spotted, e.g.:

Def	Source
Depletion of snow and ice by melting and evaporation.	NOAA National Weather Service Glossary 2009
(1) All processes that reduce the mass of the glacier. (2) The mass lost by the operation of any of the processes of sense 1, expressed as a negative number. The main processes of ablation are melting and calving (or, when the glacier nourishes an ice shelf, ice discharge across the grounding line). On some glaciers sublimation, loss of windborne snow and avalanching are significant processes of ablation. 'Ablation', unqualified, is sometimes used as if it were a synonym of surface ablation, although internal ablation, basal ablation, and frontal ablation, especially calving, can all be significant in some contexts.	Cogley et al. IACS-UNESCO Glacier Mass Balance 2011

Definitions of ablation sometimes include calving and sometimes don’t. Solution: list all ice loss processes that are listed in diverse definitions, have a general ablation class which includes them all. If users want specific combinations, they can post-compose using any of the more specific processes. If pre-composition is desired, create new terms with descriptive labels.

[rduerr]

By descriptive labels would you mean something like NOAA_ablation and Cogley_ablation?

A more problematic issue is whether ablation is a process or a mass (see Cogley definition 2)

[Garybc]

There is a process of ablation, there is an ablation zone and there are things like mass associated with that zone.

[rduerr]

I was commenting how the term ablation is used in real life to actually mean an amount of mass lost. I was trying to point out that many of the definitions in the GCW compilation actually include widely different meanings for a term. In some cases that is because different sub-communities within the cryosphere community have gone off in different directions, so that when a generalist enters the term ablation in a search they are going to expect one thing but when a mass balance glaciologist enters that same term they are going to expect a number of KG of ice removed for each glacier ....

That probably wasn't the best example to use for this, but the real issue is whether terms need to have some sort of region or discipline attached so that the definition is contextualized correctly. For example, ice - almost always means water ice for Earth Scientists. Not so for Space Scientists as there are many kinds of ice (some of which, like methane clathrate, actually are on Earth as well but haven't historically been discussed).