Wellington atmospheric ¹⁴CO₂

Overview

This is the earliest atmospheric Δ¹⁴CO₂ record and records the rise of the ¹⁴C “bomb spike”, the subsequent decline in Δ¹⁴CO₂ as bomb ¹⁴C moved throughout the carbon cycle and increasing fossil fuel CO₂ emissions further decreased atmospheric Δ¹⁴CO₂.

The seasonal cycle at Wellington is dominated by the seasonality of cross-tropopause transport, and differs slightly from that at Cape Grim, Australia, which is influenced by anthropogenic sources in winter. Δ¹⁴CO₂ at Cape Grim and Wellington show very similar trends, with significant differences only during periods of known measurement uncertainty.

The Southern Hemisphere sites show a consistent and marked elevation above the Northern Hemisphere sites since the early 2000s, which is most likely due to reduced upwelling of ¹⁴C-depleted and carbon-rich deep waters in the Southern Ocean. This developing Δ¹⁴CO₂ interhemispheric gradient is consistent with recent studies that indicate a reinvigorated Southern Ocean carbon sink since the mid-2000s, and suggests that upwelling of deep waters plays an important role in this change.