Global Outlook for Ice & Snow

G r e e n l a n d M e l t i n g o n t h e l o w e r p a r t s o f t h e s u r f a c e , i c e b e r g s c a l v e o f f f r o m i c e s h e e t e d g e s i n t o i c e f j o r d s a n d t h e s e a

A n t a r c t i c a I c e s h e l v e s , w i t h s u b g l a c i a l m e l t i n g . I c e b e r g s c a l v e o f f f r o m i c e s h e l v e s

S n o w a c c u m u l a t i o n

Equilibrium line

I c e s h e e t

I c e s h e l f

I c e f l o w

Iceberg calving

A b l a t i o n

I c e f l o w

Iceberg calving

O c e a n

Subglacial melting

Ocean

B e d r o c k

Figure 6A.1: Ice sheets. Source: based on material provided by K. Steffen, CIRES/Univ. of Colorado

climate and air composition dating back hundreds of mil- lennia. During glacial periods, ice sheets contained more than twice as much ice as that in Greenland and Antarc- tica today. Sea level would rise by about 64 m if the cur- rent mass of ice in Greenland and Antarctica were to melt

completely. Although this would take many thousands of years, recent observations show a marked increase in ice- sheet contributions to sea-level rise. In addition, ice-sheet melting strongly influences ocean salinity and tempera- ture, and also global thermohaline circulation as a con-

CHAPTER 6A

ICE SHEETS

101

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