 |
| Titel |
The impact of early Holocene Arctic shelf flooding on climate in an atmosphere–ocean–sea–ice model |
| VerfasserIn |
M. Blaschek, H. Renssen |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1814-9324
|
| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 9, no. 6 ; Nr. 9, no. 6 (2013-11-27), S.2651-2667 |
| Datensatznummer |
250085266
|
| Publikation (Nr.) |
 copernicus.org/cp-9-2651-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
| Glacial terminations are characterized by a strong rise in sea level related
to melting ice sheets. This rise in sea level is not uniform all over the
world, because regional effects (uplift and subsidence of coastal zones) are
superimposed on global trends. During the early Holocene the Siberian Shelf
became flooded before 7.5 ka BP and the coastline reached modern-day high
stands at 5 ka BP. This area is currently known as a sea-ice production area
and contributes significantly to the sea-ice exported from the Arctic through
the Fram Strait. This leads to the following hypothesis: during times of
rising sea levels, shelves become flooded, increasing sea-ice production on
these shelves, increasing sea-ice volume and export through the Fram Strait and
causing the sea-ice extent to advance in the Nordic Seas, yielding cooler and
fresher sea surface conditions. We have tested this hypothesis in an
atmosphere–ocean–sea–ice coupled model of intermediate complexity (LOVECLIM).
Our experiment on early Holocene Siberian Shelf flooding shows that in our
model sea-ice production in the Northern Hemisphere increases (15%) and
that sea-ice extent in the Northern Hemisphere increases (14%) but sea-ice
export decreases (−15%) contrary to our hypothesis. The reason of this
unexpected behaviour has its origin in a weakened polar vortex, induced by
the land–ocean changes due to the shelf flooding, and a resulting decrease of
zonality in the Nordic Seas pressure regime. Hence the winter Greenland high
and the Icelandic low strengthen, yielding stronger winds on both sides of
the Nordic Seas. Increased winds along the East Greenland Current support
local sea-ice production and transport towards the South, resulting in a
wider sea-ice cover and a southward shift of convection areas. The overall
strength of the Atlantic meridional overturning circulation is reduced by 4%
and the heat transport in the Atlantic basin by 7%, resulting in an annual
cooling pattern over the Nordic Seas by up to −4 °C. We find
that the flooding of the Siberian shelf resulting from an orbitally induced
warming and related glacioeustatic sea level rise causes a Nordic Seas
cooling feedback opposed to this warming. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|