EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Does the Natural DIC Affect the Storage of Total Inorganic Carbon in the Central Labrador Sea?

Lorenza Raimondi1,2, Toste Tanhua3, Kumiko Azetsu-Scott4, and Doug Wallace1
Lorenza Raimondi et al.
  • 1Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada
  • 2Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland
  • 3GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany.
  • 4Department of Fisheries and Oceans, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada.

The Labrador Sea plays a central role in the oceanic storage of carbon. In particular, several studies have shown that this region has amongst the highest integrated column inventories of anthropogenic carbon (Cant) in the world’s ocean. The rate at which Cant is stored in this region appears to be connected to changes in ocean circulation and can therefore vary over time. Nevertheless, it is still unclear whether the temporal variability of the total Dissolved Inorganic Carbon (DIC) inventory is solely due to the changes in Cant concentrations or whether there is a contribution of the natural component of DIC to this signal.

The Bedford Institute of Oceanography has been maintaining the Atlantic Zone Off-Shore Monitoring Program (AZOMP) in the Labrador Sea since the early 1990s. The AZOMP involves annual occupations of the AR7W line that crosses the Labrador Sea and includes sampling of DIC, as well as multiple transient tracers such as CFC-12 and SF6.  

By using observations of DIC along the AR7W line, as well as previous estimates of Cant obtained with transient tracers (using a refined version of the Transit Time Distribution method; TTD) and new estimates of Cant based on the extended Multiple Linear Regression (eMLR) method, we provide a first insight on the role that the natural component of DIC plays in the temporal variability of inorganic carbon in the central Labrador Sea between 1993 and 2016.

We show that different methods to estimate Cant can lead to different conclusions on the role of the natural variability of DIC and that these discrepancies could be related to the assumptions implied in the Cant estimation methods. In particular an analysis of Cant estimates obtained with our refined version of the TTD method in different water masses, highlighted that further refinement of the tracers’ saturation assumption could be necessary in this region. This refinement could reconcile the Cant estimates from the two methods and therefore lead to an unambiguous role of the natural DIC in this region.

How to cite: Raimondi, L., Tanhua, T., Azetsu-Scott, K., and Wallace, D.: Does the Natural DIC Affect the Storage of Total Inorganic Carbon in the Central Labrador Sea?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11982,, 2022.