 |
| Titel |
On the role of mesoscale eddies for the biological productivity and biogeochemistry in the eastern tropical Pacific Ocean off Peru |
| VerfasserIn |
L. Stramma, H. W. Bange, R. Czeschel, A. Lorenzo, M. Frank |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 11 ; Nr. 10, no. 11 (2013-11-14), S.7293-7306 |
| Datensatznummer |
250085415
|
| Publikation (Nr.) |
 copernicus.org/bg-10-7293-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
| Mesoscale eddies seem to play an important role for both the hydrography and
biogeochemistry of the eastern tropical Pacific Ocean (ETSP) off Peru.
However, detailed surveys of these eddies are not available, which has so
far hampered an in depth understanding of their implications for nutrient
distribution and biological productivity. In this study, three eddies along a
section at 16°45´ S have been surveyed intensively during R/V
Meteor cruise M90 in November 2012. A coastal mode water eddy, an open ocean
mode water eddy and an open ocean cyclonic eddy have been identified and
sampled in order to determine both their hydrographic properties and their
influence on the biogeochemical setting of the ETSP. In the thermocline the
temperature of the coastal anticyclonic eddy was up to 2 °C
warmer, 0.2 more saline and the swirl velocity was up to 35 cm s−1. The
observed temperature and salinity anomalies, as well as swirl velocities of
both types of eddies were about twice as large as had been described for the
mean eddies in the ETSP. The observed heat and salt anomalies (AHA, ASA) of
the anticyclonic eddy near the shelf-break of 17.7 × 1018 J and
36.6 × 1010 kg are more than twice as large as the mean AHA and ASA for
the ETSP. We found that the eddies contributed to the productivity by
maintaining pronounced subsurface maxima of chlorophyll of up to 6 μg
L−1. Based on a comparison of the coastal (young) mode water eddy and
the open ocean (old) mode water eddy we suggest that the ageing of eddies
when they detach from the shelf-break and move westward to the open ocean
influences the eddies' properties: chlorophyll maxima are reduced to about
half (2.5–3 μg L−1) and nutrients are subducted. However,
different settings at the time of formation may also contribute to the
observed differences between the young and old mode water eddies. The
coastal mode water eddy was found to be a site of nitrogen (N) loss in the
OMZ with a maximum ΔNO3− anomaly (i.e. N loss) of about
−25 μmol L−1 in 250 m water depth, whereas, the open ocean mode
water and cyclonic eddies were of minor and negligible importance for the N
loss, respectively. Our results show that the important role of eddies for
the distribution of nutrients, as well as biogeochemical processes in the
ETSP (and other OMZ/upwelling regions) can only be fully deciphered and
understood through dedicated high spatial and temporal resolution
oceanographic/biogeochemical surveys. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|