[MARMAM] New publication: Quantification and Analysis of Icebergs in a Tidewater Glacier Fjord Using an Object-Based Approach

Womble, Jamie jamie_womble at nps.gov
Mon Dec 5 14:57:31 PST 2016


Dear Colleagues,

We are pleased to announce the publication of the following paper in PLoS
ONE:

*Quantification and Analysis of Icebergs in a Tidewater Glacier Fjord Using
an Object-Based Approach*

The publication is available at the following link:

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0164444


*Citation: *McNabb RW, Womble JN, Prakash A, Gens R, Haselwimmer CE (2016)
Quantification and Analysis of Icebergs in a Tidewater Glacier Fjord Using
an Object-Based Approach. PLoS ONE 11(11): e0164444.
doi:10.1371/journal.pone.0164444

ABSTRACT:

Tidewater glaciers are glaciers that terminate in, and calve icebergs into,
the ocean. In addition to the influence that tidewater glaciers have on
physical and chemical oceanography, floating icebergs serve as habitat for
marine animals such as harbor seals (*Phoca vitulina richardii*). The
availability and spatial distribution of glacier ice in the fjords is
likely a key environmental variable that influences the abundance and
distribution of selected marine mammals; however, the amount of ice and the
fine-scale characteristics of ice in fjords have not been systematically
quantified. Given the predicted changes in glacier habitat, there is a need
for the development of methods that could be broadly applied to quantify
changes in available ice habitat in tidewater glacier fjords. We present a
case study to describe a novel method that uses object-based image analysis
(OBIA) to classify floating glacier ice in a tidewater glacier fjord from
high-resolution aerial digital imagery. Our objectives were to (i) develop
workflows and rule sets to classify high spatial resolution airborne
imagery of floating glacier ice; (ii) quantify the amount and fine-scale
characteristics of floating glacier ice; (iii) and develop processes for
automating the object-based analysis of floating glacier ice for large
number of images from a representative survey day during June 2007 in Johns
Hopkins Inlet (JHI), a tidewater glacier fjord in Glacier Bay National
Park, southeastern Alaska. On 18 June 2007, JHI was comprised of brash ice ( =
45.2%, SD = 41.5%), water ( = 52.7%, SD = 42.3%), and icebergs ( = 2.1%, SD
= 1.4%). Average iceberg size per scene was 5.7 m2 (SD = 2.6 m2). We
estimate the total area (± uncertainty) of iceberg habitat in the fjord to
be 455,400 ± 123,000 m2. The method works well for classifying icebergs
across scenes (classification accuracy of 75.6%); the largest
classification errors occur in areas with densely-packed ice, low contrast
between neighboring ice cover, or dark or sediment-covered ice, where
icebergs may be misclassified as brash ice about 20% of the time. OBIA is a
powerful image classification tool, and the method we present could be
adapted and applied to other ice habitats, such as sea ice, to assess
changes in ice characteristics and availability.


Feel free to contact me if you questions.


Thank you,



Jamie
*************************************
Jamie N. Womble, Ph.D.
Wildlife Biologist
National Park Service
Glacier  Bay Field Station
3100 National Park Road
Juneau, Alaska 99801 USA
907.364.1577 (phone)
907.364.2606 (fax)
http://www.nps.gov/glba/naturescience/seal.htm
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