The original version of this article has been updated in the following places:
• A sentence in the Abstract has been changed from “..566 Gt a-1 (90 m w.e.)…63 Gt a-1 (10m w.e.)…” to “..566 Gt (90 m w.e.)…63 Gt (10m w.e.)…”
• A sentence in Section 9 has been changed from “is reduced by 219.7 Gt…” to “is reduced by 224.8 Gt…”
• The y-axis labels on Figure 9 have been changed from “…balance (Gt a-1)” to “…balance (Gt)”