Modeling variations of marine reservoir ages during the last 45 000 years

• Main Authors: J. Franke, A. Paul, M. Schulz
• Format: Article
• Language: English
• Published: Copernicus Publications 2008-06-01
• Series: Climate of the Past
• Online Access: http://www.clim-past.net/4/125/2008/cp-4-125-2008.pdf

When dating marine samples with <sup>14</sup>C, the reservoir-age effect is usually assumed to be constant, although atmospheric <sup>14</sup>C production rate and ocean circulation changes cause temporal and spatial reservoir-age variations. These lead to dating errors, which can limit the interpretation of cause and effect in paleoclimate data. We used a global ocean circulation model forced by transient atmospheric Δ<sup>14</sup>C variations to calculate reservoir ages for the last 45 000 years for a present day-like and a last glacial maximum-like ocean circulation. A ~30% reduced Atlantic meridonal overturning circulation leads to increased reservoir ages by up to ~500 years in high latitudes. Temporal variations are proportional to the absolute value of the reservoir age; regions with large reservoir age also show large variation. Temporal variations range between ~300 years in parts of the subtropics and ~1000 years in the Southern Ocean. For tropical regions, which are generally assumed to have nearly stable reservoir ages, the model suggests variations of several hundred years.