A cycle solar irradiance as trigger of abrupt Holocene climatic changes and negative sea level oscillations

EDUARDO GÓMEZ, DINA E. MARTÍNEZ, GABRIELA C. CUSMINSKY

Miramar-Córdoba, Argentina

Otro; Third Joint Meeting of ICSU Dark Nature and IGCP 490; 2005

ICSU-IGCP 490

Variations in Holocene solar irradiance, recognized by the ancient atmospheric 14C relative content, show the existence of oscillations occurred during periods of time usually smaller than 150 years. Periods of maximum fluctuation and minimum values appear within a 2,300 years cycle, coinciding in some cases with globally registered abrupt climatic changes as that occurred for the so called “Little Ice Age”. According to this cycle, present trend is at midway towards a new maximum that will be occurring around 650 years from now. The general consensus in Argentina sustained that after the Last Glacial  Maximum, the mean sea level rose from depths greater than 100 m surpassing by several meters its current position reaching maximum heights at calendar ages between approximately 6,800 and 6,300 years BP, and descended almost progressively to its present position since then. However, registers of ancient sea levels show a noticeable decrement at the de la Plata River and a 3 m depth level in the Bahía Blanca Estuary, suggesting a negative sea level oscillation around cal 4,900 years BP, approximately. Analyses recently carried out on submarine sediments cropping out up to 12 m depth in the Bahía Blanca Estuary, showed the occurrence of other two important negative mean sea level oscillations at cal 7,300 and between cal 2,700 and cal 2,330 years BP. Even though there is not data suggesting the simultaneous occurrence of a local mean sea level drop corresponding to the Little Ice Age period, these negative oscillations almost coincide exactly with the 2,300 years cycle in solar irradiance mentioned above.  The fact that the MSL can be modified by several meters in relatively short periods of time suggests the existence of underestimated or even unknown mechanisms by which relatively small global climatic perturbations may have more important consequences than heretofore believed.