4000 3000 2000 1000 1000 -2000 -3000 0 4000 -5000 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 BBET 1989 1990 1991 1992 1993 1994 1995 1996 2651 1998 1999 2000 South Cascasde Sarennes 4. Refer to Figure 18.3. Echaurren Norte Figure 18.3: Glacier Mass Balance Data. 330 a. What is the overall trend in the mass balance data for the three glaciers? b. Use Your Critical Thinking Skills: When looking at mass balance data, why would it be important to analyze data over a long time span? 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018