A unit, in full the “metre [of] water equivalent”, that is an extension of the SI for describing glacier mass in specific units as the thickness of an equal mass having the density of water.
1 kg of liquid water, of density ρw = 1000 kg m–3, has a vertical extent of exactly 1 mm when distributed uniformly over a horizontal area of 1 m2. More formally, the metre water equivalent (m w.e.) is obtained by dividing a particular mass per unit area by the density of water:
1 m w.e. = 1000 kg m–2 / ρw.
Water equivalents (m w.e.) can be converted to kg m–2 by multiplying by the density of water, and to ice equivalents (m ice eq.) by multiplying by the density of water and dividing by the density of ice
Glossary of glacier mass balance and related terms. Working Group on Mass-balance Terminology and Methods of the International Association of Cryospheric Sciences (IACS)