The Legacy of A68

We cheered on iceberg A68 as it broke free in 2016 and drifted North for two years.  (Swim!  Swim free, my brother!)

In the end, A68 melted into the Atlantic, adding some fresh water to the salty ocean.

So just how much water was added?  A lot—likely more than 150 Gigatons of water. 

This winter British researchers report an analysis of A68’s lifecycle, including an estimate of how much ice it contained [2].  The analysis shows that, as might be expected, the ice melted much faster as the berg drifted North into warmer sea and air.

Fig. 1. Trajectory of A68A (circles colored by date) and historic icebergs (yellow lines, Budge and Long, 2018) overlain on a bathymetric map (GEBCO Compilation Group, 2019; Hogg et al., 2016). Selected outlines (date colour coded), altimetry overpasses (grey lines with black marking the parts that sample the iceberg) and key dates are also shown. Panels b and c are zoom regions of interest. (From [2])

150 Gt is literally a drop in the ocean (which has something like a billion Gt of water), but is potentially significant in the immediate area of the melting berg.  This is why it matters where the ice melts—the fresh water impacted the Scotia Sea where the berg ended, not the Weddell Sea where it started. 

“Their freshwater inputs will alter local currents. And all the iron, other minerals, and even organic matter picked up through their lives and subsequently dropped into the ocean will seed biological production.”

(From [1])

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1. Jonathan Amos, A68: ‘Megaberg’ dumped huge volume of fresh water, in BBC News – Science & Environment, January 20, 2022. https://www.bbc.com/news/science-environment-60060299
2. A. Braakmann-Folgmann, A. Shepherd, L. Gerrish, J. Izzard, and A. Ridout, Observing the disintegration of the A68A iceberg from space. Remote Sensing of Environment, 270:112855, 2022/03/01/ 2022. https://www.sciencedirect.com/science/article/pii/S0034425721005757