Black carbon and the North Pole

Santa’s Smoky Summer

You may have read headlines that smoke from severe wildfires (mainly in boreal forests) in Siberia had reached the North Pole for the first time ever. Many of these media pieces cite a NASA MODIS daily website from 7 August 2021 indicating that this might be the first time in recorded history. FYI: the Moderate Resolution Imaging Spectroradiometer, or MODIS, is a sensor onboard two polar-orbiting satellites - Terra and Aqua - so there are four daily snapshots of most locations on Earth. MODIS has been capturing images since approximately November 1999 onboard Terra and May 2002 onboard Aqua.

This MODIS Aqua images from 7 August 2021 shows extent of smoke over Sakha Republic, Russian Federation. In the write-up to this post, it is mentioned that this documented smoke transport to the Arctic Ocean and the North Pole is “a feat that appears to be a first in recorded history”. URL: https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2021-08-07

• Is this truly the first time smoke has reached the North Pole? Likely not.

There have been other more extreme fire years in Sakha Republic and Siberia as region than 2021 or 2020.

• Is this the first time we have been able to document this with near real-time satellite data? That’s probably the right answer.

Modeling research teams, like NASA’s Global Modeling and Analysis Office, provide historical accounting of the most statistically robust and comprehensive records of location and quantity of aerosols (i.e., particulate matter and smoke). For instance, they currently provide a re-analysis product that uses MERRA-2 data going back to 1979. That’s before I was born! How? MERRA-2 also includes observations from GPS data in addition to Earth observation satellites. [Huge shoutout to Dr. Peter Griffith of NASA GSFC for giving me the idea to look into. ]

Black Carbon and Sea Ice

Why do we care about black carbon deposition in the Arctic Ocean (AKA the North Pole)?

This is an albedo issue. If you have ever taken a black towel to a white sand beach, then you understand that darker surfaces are hotter in the direct sun than lighter surfaces (and ow, ow, OW - those dark towels can be pretty hot on the old derrière).

Black carbon, which you can think of as the dark part of smoke, can deposit - or land - onto sea ice in the Arctic at any time of the year. Of course, when the sun is shining that means more energy is absorbed by these dark soot pieces and - VOILA! - you have melt.

The science of how black carbon deposition occurs is very mature. Here, a figure from the 2011 Arctic Monitoring and Assessment Programme’s (AMAP) report on black carbon shows how that happens. URL: https://www.amap.no/documents/doc/the-impact-of-black-carbon-on-arctic-climate/746.

Black carbon deposition is most critical in the late winter and spring, because that’s when insolation (i.e., the Sun’s energy) is increasing in the Northern Hemisphere and also when sea ice is at its maximum extent. Preventing human-caused fires in the spring throughout the temperate zone and north (think anything 40°N and above in latitude across the globe) is a good way to prevent black carbon deposition and subsequent melt of sea ice. However, industrial and energy - including oil and natural extraction and flaring - are the leading sources and we must reduce those as well - particularly as they are directly related to human activity and control. The science behind this is very well established and I encourage you to read AMAP’s Impacts of Short-lived Climate Forcers on Arctic Climate, Air Quality, and Human Health: Summary for Policy-makers published in 2021. [Disclaimer: I am a contributor to this publication].

So what about the summer? Well, a couple things are happening. First, sea ice extent is decreasing rapidly in the summer, and so its extent is just not as much. Meaning that any smoke transport to the Arctic will deposit into the ocean and not on ice. Second, solar insolation is starting to wane after the summer solstice - pretty quickly for high northern latitudes. Any deposition on what sea ice is left is not being heated as much - though of course, this can still cause melt.

Now what?

Well, now we reduce warming through climate action. We also can reduce human sources of black carbon - like moving away from fossil fuels and replacing them with renewable energy, reducing emissions from industry via clean technology and diversification of products, and reducing human-caused burning in agricultural landscapes and wildlands during those important winter and spring months when transport is happening.

You don’t have to do it for me. Do it for the reindeer.

Photo by Nicolas Lafargue on Unsplash. Reindeer eating lichen through the snow, near Tromsø, Norway (Sami Arctic reindeer, sekundær fylkesvei 53, krokelvdalen, norvège).

Thumbnail image and social media image from: NASA GSFC MODIS Science Team (https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2021-08-07).