Henning Cara C.

No Thumbnail Available
Last Name
Henning
First Name
Cara C.
ORCID

Filters

2005 - 2006 2
2
2
Reset filters

Settings

Search Results

Now showing 1 - 2 of 2
  • Article
    Wintertime phytoplankton bloom in the subarctic Pacific supported by continental margin iron
    (American Geophysical Union, 2006-02-01) Lam, Phoebe J. ; Bishop, James K. B. ; Henning, Cara C. ; Marcus, Matthew A. ; Waychunas, Glenn A. ; Fung, Inez Y.
    Heightened biological activity was observed in February 1996 in the high-nutrient low-chlorophyll (HNLC) subarctic North Pacific Ocean, a region that is thought to be iron-limited. Here we provide evidence supporting the hypothesis that Ocean Station Papa (OSP) in the subarctic Pacific received a lateral supply of particulate iron from the continental margin off the Aleutian Islands in the winter, coincident with the observed biological bloom. Synchrotron X-ray analysis was used to describe the physical form, chemistry, and depth distributions of iron in size fractionated particulate matter samples. The analysis reveals that discrete micron-sized iron-rich hot spots are ubiquitous in the upper 200 m at OSP, more than 900 km from the closest coast. The specifics of the chemistry and depth profiles of the Fe hot spots trace them to the continental margins. We thus hypothesize that iron hot spots are a marker for the delivery of iron from the continental margin. We confirm the delivery of continental margin iron to the open ocean using an ocean general circulation model with an iron-like tracer source at the continental margin. We suggest that iron from the continental margin stimulated a wintertime phytoplankton bloom, partially relieving the HNLC condition.
  • Article
    Extending the record of photosynthetic activity in the eastern United States into the presatellite period using surface diurnal temperature range
    (American Geophysical Union, 2005-04-26) Bonfils, Celine ; Angert, Alon ; Henning, Cara C. ; Biraud, Sebastien ; Doney, Scott C. ; Fung, Inez Y.
    In this study, we demonstrate that mid-latitude surface measurements of diurnal temperature range (DTR) can be used to reconstruct decadal variability of regional-scale terrestrial photosynthetic activity 1) during and prior to the period with satellite retrievals of land greenness and 2) without the need for moisture data. While the two relative maxima present in the seasonal evolution of DTR can determine the beginning and the end of the growing season, the summertime average DTR can be used as a proxy of summertime terrestrial photosynthesis. In a case study in the eastern United States (1966–1997), the DTR reconstructions indicate significant natural decadal variability in photosynthetic activity, but no secular, long-term trend. The summertime photosynthesis was found to be controlled primarily by moisture availability. Also, contrary to existing model parameterizations, the timing of spring onset was found to depend on both temperature and moisture.