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| Titel |
Strong North Atlantic Subtropical Gyre circulation fueling moisture advection into the Mediterranean realm during the Mid-Pleistocene Transition |
| VerfasserIn |
André Bahr, Stefanie Kaboth, David Hodell |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250141363
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| Publikation (Nr.) |
 EGU/EGU2017-4867.pdf |
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| Zusammenfassung |
| The wind-driven North Atlantic Subtropical Gyre is an important mediator of heat and
moisture advection into central and southern Europe. Here we study the dynamics of the
Subtropical Gyre during the mid-Pleistocene (approx. 1400 – 500 ka; MIS 44 – 14). This
time interval is characterized by a profound increase in continental ice shield size and the
switch from a 41 kyr to a ∼100 kyr glacial/interglacial cyclicity (“Mid-Pleistocene
Transition”, MPT). Primary goal was to investigate the response of the Subtropical
Gyre to changes in the boundary conditions (e.g. ice volume) over the course of
the MPT. Our interpretation is based on paired δ18O and Mg/Ca analyses on the
thermocline-dwelling planktonic foraminifera Globorotalia inflata from Iberian Margin Site
U1385 reflecting subsurface temperature and salinity variability at the eastern branch of the
Subtropical Gyre. The results show generally cold/fresh glacials and warm/saline
interglacials on thermocline level. Hence, advection of warm/saline subtropical
waters is generally stronger during interglacials than during glacials. However,
glacials MIS 20 and 18 stand out as they are characterized by anomalously warm and
saline subsurface waters off Iberia. We infer that enhanced ice shield growth during
the MPT led to a southward shift of the source region of the thermocline waters
at the Iberian Margin. Combined with increased Ekman downwelling (causing a
deepened thermocline) this effectively counteracted glacial subsurface cooling at
Site U1385. The eccentricity minimum during MIS 20–18 further suppressed the
development of strong trade winds and, hence, the advection of cold northern-sourced
water masses. Relatively humid conditions in the eastern Mediterranean during
MIS 20 and 18 indicate that atmospheric moisture derived from the warm water
accumulated off Iberia might have been advected deep into continental Europe. It might be
perceived that this moisture further fueled European glacier growth during the MPT. |
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