12 December, 2013 – Presented at an invited American Geophysical Union (AGU) talk, a calculation enabled based on our field data indicate:
- The likely 2012 albedo drop from black carbon, through amplifying feedback with sunlight, doubles for the ice sheet as a whole through the melt season.
- Summer 2012 black carbon concentrations likely increased cumulative surface net heating by 20-40% for the ice sheet as a whole.
- In low elevation areas where snow cover overlies impurity rich bare ice, the feedback multiplication can be more than a factor of 5 lower albedo than the hypothetical case with no black carbon.
- The sensitivity of the ice sheet to light absorbing impurities is high, especially in areas with seasonal snow cover that when melted away earlier, lead to more surface melting.
- The sensitivity to light absorbing impurities is greatest when there is little summer snowfall. The snowfall brightens the surface and shields, at least partially, the dark particles from the sunlight. Low summer snowfall prevailed in 2012 and other years with negative Arctic Oscillation Index.
The AGU presentation is watchable online using “AGU13” as the passcode and searching “black carbon” to find the talk entitled “examining the role of black carbon and microbial abundance in Greenland ice sheet albedo feedback“.
Alluded to in the talk’s title and this video below is that the science is evolving to tackle another key aspect of cryosphere climate sensitivity, the importance of microbial abundance in Greenland ice sheet albedo feedback. So, stay tuned. The Dark Snow Project is gaining momentum!