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Precession‐ and obliquity‐induced changes in moisture sources for enhanced precipitation over the Mediterranean Sea

Precession‐ and obliquity‐induced changes in moisture sources for enhanced precipitation over the Mediterranean Sea
Precession‐ and obliquity‐induced changes in moisture sources for enhanced precipitation over the Mediterranean Sea
Enhanced winter precipitation over the Mediterranean Sea at times of minimum precession and maximum obliquity, that is, times of enhanced insolation seasonality, could provide freshwater required to form orbitally paced sedimentary cycles across the Mediterranean, offering a possible alternative to monsoonal runoff. We investigate the sources of the enhanced winter precipitation, by applying a moisture tracking model on the results of idealized orbital extreme experiments with a state‐of‐the‐art climate model. Precession and obliquity enhance precipitation in fall and winter. Our study shows that the source of enhanced precipitation over the Mediterranean Sea differs during the winter half‐year. In fall, the majority of the precession‐induced precipitation increase originates from the Mediterranean itself. However, in late winter, the increase can be attributed to enhanced moisture advection from the Atlantic. This agrees with changes in evaporation and air‐sea temperature differences over the Mediterranean. The obliquity‐induced precipitation increase shows much less differences, with an equal contribution of local and Atlantic sources. The mechanism behind the Atlantic source of moisture, particularly important in late winter for precession‐induced precipitation changes, is related to a weakened Azores High and slightly higher surface pressure over North Africa. The resulting anomalous circulation patterns generate enhanced Atlantic moisture transport toward the Mediterranean. These mechanisms coincide with weaker storm track activity over the North Atlantic, opposite to previous studies that often attribute enhanced Mediterranean winter precipitation to a southward shift and intensification of the Atlantic storm track. We thus provide an alternative mechanism for Atlantic sources of orbitally paced Mediterranean precipitation changes.
Mediterranean, moisture tracking, obliquity, precession, precipitation, sapropel
2572-4517
Bosmans, J.H.C.
20249d98-78a4-49c4-9bc0-880cecef0662
van der Ent, R.J.
aae21837-06ed-4cc9-a7ae-b6192978be48
Haarsma, R.J.
52de705c-7df6-48c6-a891-99c8a01f4b09
Drijfhout, S.S.
a5c76079-179b-490c-93fe-fc0391aacf13
Hilgen, F.J.
afa55c8c-67ff-47c9-b1c7-d1f50cc2e253
Bosmans, J.H.C.
20249d98-78a4-49c4-9bc0-880cecef0662
van der Ent, R.J.
aae21837-06ed-4cc9-a7ae-b6192978be48
Haarsma, R.J.
52de705c-7df6-48c6-a891-99c8a01f4b09
Drijfhout, S.S.
a5c76079-179b-490c-93fe-fc0391aacf13
Hilgen, F.J.
afa55c8c-67ff-47c9-b1c7-d1f50cc2e253

Bosmans, J.H.C., van der Ent, R.J., Haarsma, R.J., Drijfhout, S.S. and Hilgen, F.J. (2020) Precession‐ and obliquity‐induced changes in moisture sources for enhanced precipitation over the Mediterranean Sea. Paleoceanography and Paleoclimatology, 35 (1), [e2019PA003655]. (doi:10.1029/2019PA003655).

Record type: Article

Abstract

Enhanced winter precipitation over the Mediterranean Sea at times of minimum precession and maximum obliquity, that is, times of enhanced insolation seasonality, could provide freshwater required to form orbitally paced sedimentary cycles across the Mediterranean, offering a possible alternative to monsoonal runoff. We investigate the sources of the enhanced winter precipitation, by applying a moisture tracking model on the results of idealized orbital extreme experiments with a state‐of‐the‐art climate model. Precession and obliquity enhance precipitation in fall and winter. Our study shows that the source of enhanced precipitation over the Mediterranean Sea differs during the winter half‐year. In fall, the majority of the precession‐induced precipitation increase originates from the Mediterranean itself. However, in late winter, the increase can be attributed to enhanced moisture advection from the Atlantic. This agrees with changes in evaporation and air‐sea temperature differences over the Mediterranean. The obliquity‐induced precipitation increase shows much less differences, with an equal contribution of local and Atlantic sources. The mechanism behind the Atlantic source of moisture, particularly important in late winter for precession‐induced precipitation changes, is related to a weakened Azores High and slightly higher surface pressure over North Africa. The resulting anomalous circulation patterns generate enhanced Atlantic moisture transport toward the Mediterranean. These mechanisms coincide with weaker storm track activity over the North Atlantic, opposite to previous studies that often attribute enhanced Mediterranean winter precipitation to a southward shift and intensification of the Atlantic storm track. We thus provide an alternative mechanism for Atlantic sources of orbitally paced Mediterranean precipitation changes.

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More information

Accepted/In Press date: 9 January 2020
e-pub ahead of print date: 21 January 2020
Published date: January 2020
Additional Information: Funding Information: ). The climatological monthly mean output of the simulations is available through Zenodo: Bosmans ( ). Idealized orbital extreme GCM simulations with EC‐Earth‐2‐2 [Data set]. Zenodo ( ; van der Ent et al., ) is available for download at: van der Ent, R. J.: WAM2layersPython ( The authors thank two anonymous reviewers for their comments, which helped to improve the manuscript. The EC‐Earth simulations were performed as part of J. H. C. Bosmans' PhD project within Utrecht University's “Focus en Massa” call. Modeling support was provided by the Royal Netherlands Meteorological Institute (KNMI) and the European Centre for Medium‐Range Weather Forecast (ECMWF). The WAM2 layer simulations were performed at the Cartesius SurfSara supercomputing facilities. Details on the EC‐Earth setup and orbital forcing can be found in Bosmans ( http://doi.org/10.5281/zenodo.3268528 ). Higher temporal resolution output (12‐hourly or daily) can be obtained from the lead author. The WAM2 layer model code (van der Ent, https://github.com/ruudvdent/WAM2layersPython ), last access: 23 November 2016. Publisher Copyright: ©2020. American Geophysical Union. All Rights Reserved.
Keywords: Mediterranean, moisture tracking, obliquity, precession, precipitation, sapropel

Identifiers

Local EPrints ID: 439774
URI: http://eprints.soton.ac.uk/id/eprint/439774
ISSN: 2572-4517
PURE UUID: 8aab68b8-0ad2-4a55-b2ab-ec7ae75c515f

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Date deposited: 01 May 2020 16:40
Last modified: 08 Sep 2022 17:36

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Contributors

Author: J.H.C. Bosmans
Author: R.J. van der Ent
Author: R.J. Haarsma
Author: S.S. Drijfhout
Author: F.J. Hilgen

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