Investigating the role of air mass history on the diversity of GCMestimates of atmospheric black carbon in the Arctic

• Black Carbon (BC) aerosols are known to play an important role in the Arctic, yet their exact contribution to thechanging of the Earth’s climate and Arctic amplification remains unclear. To reduce these uncertainties, the life cycle of BCneeds to be accurately described in general circulation models (GCMs). In this study, four GCMs (ECHAM6.3-HAM2.3,ECHAM6.3-HAM2.3-P3, ECHAM6.3-HAM2.3-SALSA2 and UKESM1.0) are compared in terms of their representation ofBC in the Arctic. A new Lagrangian framework is applied to investigate the history of airmasses reaching the Arctic observationalsite Zeppelin on Svalbard, and compared to the corresponding transport simulated by the GCMs, which are allnudged to reanalysis data from ERA-Interim. Aerosol processes along the trajectories are then compared between the models.ECHAM6.3-HAM2.3-P3 simulates the highest and UKESM1.0 the lowest BC loadings both globally and within the Arcticand ECHAM6.3-HAM2.3-SALSA2 is the GCM that reproduces the observations from Zeppelin station most faithfully. The BC concentration in the Arctic is largely controlled by the wet removal processes described in the models, but dry depositionalso plays a role in explaining some of the inter-model diversity. ECHAM6.3-HAM2.3-P3 is less efficient in wet removal thanthe other models, which is likely a result of an adjusted representation of ice processes compared with the other two ECHAMvariants. UKESM1.0 is the most efficient model in removing BC from the atmosphere, in large part due to more efficient dryremoval than with the ECHAM models. The Lagrangian analysis reveals that the BC concentrations at the Zeppelin station are largely determined by concentrations in airmasses older than the length of our back trajectories, i.e. ten days, highlighting theimportance of remote emissions to local BC concentrations in the Arctic. This further suggests a longer BC lifetime within theArctic as compared with the global average. Our results underline the importance of accurate descriptions of cloud and precipitation microphysics, along with realistic dry and wet scavenging schemes for improved descriptions of BC and its climateimpacts in the Arctic within GCMs.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Environmental Sciences (hsv//eng)

Nyckelord

Black Carbon

Aerosols

Artic

scavenging

lifecyle

Aerocom

Environmental Sciences

miljövetenskap

atmosfärvetenskap och oceanografi

Atmospheric Sciences and Oceanography

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)