Ocean carbon inventory under warmer climate conditions – the case of the Last Interglacial
<p>During the Last Interglacial period (LIG), the transition from 125 to 115 ka provides a case study for assessing the response of the carbon system to different levels of high-latitude warmth. Elucidating the mechanisms responsible for interglacial changes in the ocean carbon inve...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-12-01
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| Series: | Climate of the Past |
| Online Access: | https://www.clim-past.net/14/1961/2018/cp-14-1961-2018.pdf |
| Summary: | <p>During the Last Interglacial period (LIG), the transition from 125 to 115 ka
provides a case study for assessing the response of the carbon system to
different levels of high-latitude warmth. Elucidating the mechanisms
responsible for interglacial changes in the ocean carbon inventory provides
constraints on natural carbon sources and sinks and their climate
sensitivity, which are essential for assessing potential future changes.
However, the mechanisms leading to modifications of the ocean's carbon budget
during this period remain poorly documented and not well understood. Using a
state-of-the-art Earth system model, we analyze the changes in oceanic carbon
dynamics by comparing two quasi-equilibrium states: the early, warm Eemian
(125 ka) versus the cooler, late Eemian (115 ka). We find considerably
reduced ocean dissolved inorganic carbon (DIC; <span class="inline-formula">−314.1</span> PgC) storage in the
warm climate state at 125 ka as compared to 115 ka, mainly attributed to
changes in the biological pump and ocean DIC disequilibrium components. The
biological pump is mainly driven by changes in interior ocean ventilation
timescales, but the processes controlling the changes in ocean DIC
disequilibrium remain difficult to assess and seem more regionally affected.
While the Atlantic bottom-water disequilibrium is affected by the
organization of sea-ice-induced southern-sourced water (SSW) and
northern-sourced water (NSW), the upper-layer changes remain unexplained. Due
to its large size, the Pacific accounts for the largest DIC loss,
approximately 57 % of the global decrease. This is largely associated
with better ventilation of the interior Pacific water mass. However, the
largest simulated DIC differences per unit volume are found in the SSWs of
the Atlantic. Our study shows that the deep-water geometry and ventilation in
the South Atlantic are altered between the two climate states where warmer
climatic conditions cause SSWs to retreat southward and NSWs to extent
further south. This process is mainly responsible for the simulated DIC
reduction by restricting the extent of DIC-rich SSW, thereby reducing the
storage of biological remineralized carbon at depth.</p> |
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| ISSN: | 1814-9324 1814-9332 |