Tuesday, February 3, 2009

weekly update

Hi all, more progress has been made in the past week, and since I'm
too lazy to report on all of it in my own words, here are some
excerpts from the weekly report. Ask questions on any part that's
unclear and I'll try to give a decent explanation:

In certain parts of North America, February 2nd is when a furry
creature is said to emerge from its burrow and, depending on shadows
seen, there could be several more weeks of winter. Here in the
Amundsen, a furry creature emerged from the sea early today to
inspect a ongoing ice buoy deployment, and the weather turned from
fair to foggy. Whether or not any shadows were cast, forward progress
has been slowed somewhat by the elements as we enter late summer and
the second half of NBP09-01.

Autosub prep work and forays under the PIG kept the ship within a
half day of the ice front for most of the week, resulting in fairly
comprehensive coverage of the inner Pine Island Bay (PIB), as another
1522 km of seafloor were swath-mapped. Twenty four CTD - LADCP -
rosette stations were occupied, bringing the total for that activity
to 111, and documenting upwelling near the center of a clockwise gyre
in the bay. Temporal and spatial water column variability is
relatively high in the upper 400 m, but with coherent extrema in
meltwater content, light scattering and other parameters. XBT casts
were made along the ice front, during which the height of the
'barrier' was calculated at regular intervals using radar range and a
ship's sextant, while its its draft was estimated from multibean side-

[The sea ice team] sampled fast ice southeast of the Thwaites Glacier
Tongue and near the northern end of its sea ice extension, and
deployed two GPS ice motion transmitters on mobile pack north of the
fast ice to monitor drift and deformation. To date they have occupied
8 sites, obtaining 46.5 meters of ice core, from which 331 sections
have been sampled for salinity and d18O, and 163 for chl-a. Mean ice
core thickness is 160 cm, but has ranged from 47 to 469 cm.
Structural analysis of 12 cores includes 137 thin sections revealing
large amounts of complex granular ice and a wide range of crystal
sizes. In addition, meteoric ice appears to comprise a substantial
fraction of the ice in some cores, mainly snow ice from seawater
flooding, with thin layers of superimposed ice from refrozen snow
melt perched above in most cores.

Eleven TMC [trace metal clean] casts were completed this past week to
sample for Fe, organic ligands and phytoplankton parameters and 2 for
large-volume surface water experiments. Six were taken while
transiting a persistent (6 week) area of high phytoplankton biomass
shown by satellite ocean color (chlorophyll) imagery. The responsible
agent is Phaeocystis antarctica, and the high productivity was
accompanied by extremely low surface values of pCO2.

[The photographers] have been busy documenting operations by still
camera and video, some from the zodiac during Asub retrievals, along
with sea ice coring, CTD/rosette work and upwelling near the PIG. Ice
crystals have been photographed under polarized light, the bottom of
the sea ice via a camera lowered through an ice hole, and icebergs
and ice fronts captured in all their revealing detail. They have also
interviewed science personnel, some more willing than others, and are
grateful for the access and cooperation provided.

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