Climate change is transforming the Arctic Ocean in unprecedented ways which can be most directly observed in the systematic decline in seasonal ice coverage. From the collection and analysis of particulate and dissolved activities of210Po and210Pb from four deepwater superstations, as a part of the US Arctic GEOTRACES cruise during 2015, and in conjunction with previously published data, the temporal and spatial variations in their activities, inventories and residence times are evaluated. The results show that the partitioning of particulate and dissolved phases has changed significantly in the 8 years between 2007 and 2015, while the total210Po and210Pb activities have remained relatively unchanged. Observed total210Po/210Pb activity ratio was less than unity in all deepwater stations, implying disequilibria in the entire water column. From the distribution of total210Po and210Pb in the upper 500 m of all major Arctic Basins, the derived scavenging efficiencies decrease as per the following sequence: Makarov Basin > Gakkel Bridge > Canada Basin Nansen Basin ∼ Amundsen Basin > Alpha Ridge, which is the reverse order of the calculated residence times of210PoT. The scavenging intensities differ between the fully ice‐covered, partially ice‐covered, and no ice‐covered stations, as observed from the differences in the average activities of210Po and210Pb. The average settling velocity of particulate matter based on the210Pb activity is similar to the published values based on230Th, indicating removal mechanism(s) of Th and Pb is (are) similar.
A striking example is presented of a newly observed phenomenon in the ice‐covered Arctic Ocean that appears to be a consequence of changes in the physical forcing. In summer 2011, a massive phytoplankton bloom was observed north of the Bering Strait, between Russia and the United States, underneath pack ice that was a meter thick—in conditions previously thought to be inconducive for harboring such blooms. It is demonstrated that the changing ice cover, in concert with the resulting heat exchange between the atmosphere and ocean, likely led to this paradigm shift at the base of the food chain by altering the supply of nutrients and sunlight. Such early‐season under‐ice blooms have the potential to profoundly alter the Arctic food web.
more » « less- Award ID(s):
- 1733564
- NSF-PAR ID:
- 10463340
- Publisher / Repository:
- DOI PREFIX: 10.16995
- Date Published:
- Journal Name:
- Zygon®
- Volume:
- 53
- Issue:
- 2
- ISSN:
- 0591-2385
- Format(s):
- Medium: X Size: p. 496-506
- Size(s):
- ["p. 496-506"]
- Sponsoring Org:
- National Science Foundation
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