Positive degree-day factors for ablation on the Greenland ice sheet studied by energy-balance modelling

• Main Author: Roger J. Braithwaite
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1995
• Subjects: Bala; Greenland; Ice Sheet
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.634.5942; http://www.igsoc.org/journal/41/137/igs_journal_vol41_issue137_pg153-160.pdf

ABSTR ACT. Ice a b la tion is rel a ted to a ir temperature b y the positive d egree-day factor. V a ri a tions of th e positi ve degree-d ay fac tor in \Ves t Greenland a re st ud ied using a n energy-ba la n ce m odel to simulate ablation under differen t condi tions. Degree-d ay factors for simula ted a nd m easured ice a bla tio n at;.Jordbogle tscher a nd Q amana rss up sermia agree well with valu es a round 8 mm d 1oC I. Degree-d ay factors for snow a re less tha n h a lf those for ice. Energy-bala nce m od ell ing shows th a t degree-day factors va ry with summer mean tempera ture, surface a lbedo and turbulence but there is only evidence of la rge positive d egree-day facto rs a t lower tempera tures and with low a lbedo (0. 3). Th e greates t effec t of albedo varia ti o ns (0.3- 0. 7) is a t lower tempera tures while vari a tio ns in turbulen ce have grea ter e ITeC! a t higher tempera tures. Current m odels may underes tima te rllnoff from the Green la nd ice shee t b y severa l tenths becallse they use a d egree-day facto r for melting ice tha t is too sm a ll fo r the cold er pa rts of the ice shee t, i.e. the upper a bla tion a rea a nd the northerly m a rgin.