The firn meltwater Retention Model Intercomparison Project (RetMIP): evaluation of nine firn models at four weather station sites on the Greenland ice sheet

TY - JOUR

T1 - The firn meltwater Retention Model Intercomparison Project (RetMIP)

T2 - evaluation of nine firn models at four weather station sites on the Greenland ice sheet

AU - Vandecrux, B.

AU - Mottram, R.

AU - Langen, P. L.

AU - Fausto, R. S.

AU - Olesen, M.

AU - Stevens, C. M.

AU - Verjans, V.

AU - Leeson, A.

AU - Ligtenberg, S.

AU - Kuipers Munneke, P.

AU - Marchenko, S.

AU - van Pelt, W.

AU - Meyer, C. R.

AU - Simonsen, S. B.

AU - Heilig, A.

AU - Samimi, S.

AU - Marshall, S.

AU - Machguth, H.

AU - MacFerrin, M.

AU - Niwano, M.

AU - Miller, O.

AU - Voss, C. I.

AU - Box, J. E.

PY - 2020/11

Y1 - 2020/11

N2 - Perennial snow, or firn, covers 80% of the Greenland ice sheet and has the capacity to retain surface meltwater, influencing the ice sheet mass balance and contribution to sea-level rise. Multilayer firn models are traditionally used to simulate firn processes and estimate meltwater retention. We present, intercompare and evaluate outputs from nine firn models at four sites that represent the ice sheet's dry snow, percolation, ice slab and firn aquifer areas. The models are forced by mass and energy fluxes derived from automatic weather stations and compared to firn density, temperature and meltwater percolation depth observations. Models agree relatively well at the dry-snow site while elsewhere their meltwater infiltration schemes lead to marked differences in simulated firn characteristics. Models accounting for deep meltwater percolation overestimate percolation depth and firn temperature at the percolation and ice slab sites but accurately simulate recharge of the firn aquifer. Models using Darcy's law and bucket schemes compare favorably to observed firn temperature and meltwater percolation depth at the percolation site, but only the Darcy models accurately simulate firn temperature and percolation at the ice slab site. Despite good performance at certain locations, no single model currently simulates meltwater infiltration adequately at all sites. The model spread in estimated meltwater retention and runoff increases with increasing meltwater input. The highest runoff was calculated at the KAN_U site in 2012, when average total runoff across models (2) was 353610mmw.e. (water equivalent), about 2748% of the surface meltwater input. We identify potential causes for the model spread and the mismatch with observations and provide recommendations for future model development and firn investigation.

AB - Perennial snow, or firn, covers 80% of the Greenland ice sheet and has the capacity to retain surface meltwater, influencing the ice sheet mass balance and contribution to sea-level rise. Multilayer firn models are traditionally used to simulate firn processes and estimate meltwater retention. We present, intercompare and evaluate outputs from nine firn models at four sites that represent the ice sheet's dry snow, percolation, ice slab and firn aquifer areas. The models are forced by mass and energy fluxes derived from automatic weather stations and compared to firn density, temperature and meltwater percolation depth observations. Models agree relatively well at the dry-snow site while elsewhere their meltwater infiltration schemes lead to marked differences in simulated firn characteristics. Models accounting for deep meltwater percolation overestimate percolation depth and firn temperature at the percolation and ice slab sites but accurately simulate recharge of the firn aquifer. Models using Darcy's law and bucket schemes compare favorably to observed firn temperature and meltwater percolation depth at the percolation site, but only the Darcy models accurately simulate firn temperature and percolation at the ice slab site. Despite good performance at certain locations, no single model currently simulates meltwater infiltration adequately at all sites. The model spread in estimated meltwater retention and runoff increases with increasing meltwater input. The highest runoff was calculated at the KAN_U site in 2012, when average total runoff across models (2) was 353610mmw.e. (water equivalent), about 2748% of the surface meltwater input. We identify potential causes for the model spread and the mismatch with observations and provide recommendations for future model development and firn investigation.

KW - DENSIFICATION

KW - ENERGY-BALANCE

KW - LAYER FORMATION

KW - LOWER ACCUMULATION AREA

KW - RUNOFF

KW - SNOW

KW - STORAGE

KW - SURFACE MASS-BALANCE

KW - THERMAL-CONDUCTIVITY

KW - WATER-MOVEMENT

UR - http://www.scopus.com/inward/record.url?scp=85092284625&partnerID=8YFLogxK

U2 - 10.5194/tc-14-3785-2020

DO - 10.5194/tc-14-3785-2020

M3 - Journal article

SN - 1994-0424

VL - 14

SP - 3785

EP - 3810

JO - The Cryosphere

JF - The Cryosphere

IS - 11

ER -