Monday, February 9, 2009

Weekly Report Time!

Hi everyone,

Cranking out oxygens today and working hard on my talk (in four
minute intervals between samples), so it's fortunate that it;s weekly
report time -- means I have less writing to do (wouldn't want to
overwhelm my readership...).

One quick note though -- first sunrise/sunset in over a month last
night. Down around 3, up at 5 or so. We've been heading north as
the days have been getting shorter. Supposedly the night shift got
quite a visual treat. I saw some orange, but had to head to bed
after. I'll try to stay up for some of the excitement tonight but
cloudy skies may dull the glow.

The report follows, with only minor edits:

Fifteen years ago next to nothing was known about the bathymetry and
ocean circulation on the Amundsen Sea continental shelf, a nearly
inaccessible backwater presumed to have little relevance to such
weightier topics as Antarctic Bottom Water formation and biological
productivity, much less to ice shelf dynamics. However, unimagined
and highly relevant sea floor topography and oceanographic processes
have since been found lurking beneath its nearly perennial sea ice
cover. The deep troughs cut by larger ice streams during past glacial
epochs are now being filled by 'warm' deep water, speeding wastage of
the glaciers that carved them. Melt-driven upwelling of water
enriched in glacial flour drives persistent algal blooms, at odds
with conventional boom and bust cycles of macro/micro-nutrient
limited regions. Downwelling doesn't much matter here, but the
upwelling transports ocean heat to the floating and thinning parts of
the West Antarctic Ice Sheet.

Recent Amundsen expeditions, initially on the NB Palmer and
subsequently on Polarstern and JC Ross, have defined the late summer
water properties on the Amundsen continental shelf and provided
indications of their interannual variability. But longer and more
continuous records are needed to determine how this regional sea is
responding to seasonal and other atmospheric cycles, and causing the
increased melting of continental ice. That work began modestly 3
years ago with the setting of several simple near-bottom instrument
packages, some showing expected and others unexpected results when
recovered a year later. As this IPY draws to a close, we are setting
out more heavily instrumented moorings for longer periods and over a
broader area. The focus is on temperature, the primary gauge of
subsurface change, and on deep water inflow at depths >400 m,
lessening the risks posed by hundreds of large icebergs that infest
the eastern Amundsen. Nine bottom-anchored moorings have been
deployed to date on 0901, and another five should be added to the
array during the next week.

Those moorings must be recovered to retrieve the recorded data, but
we have also set out, on fast ice east of Bear Peninsula, an Ice
Tethered Profiler that knows how (if not when) to call home and
report its measurements. A joint effort with Woods Hole investigators
Toole & Timmermans, this is the first ITP deployment in the
Antarctic, following ~30 that have been placed on drifting pack ice
in the Arctic. The fast ice is thinner than we would have liked, with
seal holes nearby and a sporadic break-out record. But ice options
were slim this year, and with a bit of luck it will remain fast until
a daily 750 meter-depth record of temperature and salinity can be
generated over several seasons.

Shortly after leaving the idyllic conditions of Pine Island Bay,
progress was hampered by fog and ice, then high winds, confused seas
and cruise time contraints led to the cancellation of CTD profiling
transects near two ice shelf fronts. A 15-hour round trip back to the
fast edge turned into a wild goose chase, but a large raft of
penguins (>75) were observed there, all in Emperor's formal dress. A
non-functional sea ice buoy on one ice floe replaced a curious piece
of rubber flotsam from another. Fisherfolk were encountered occupying
a planned station site, and other fishing boats called to alert us
that they were (temporarily?) beset nearby. All are believed to be
longlining for toothfish (Chilean Sea Bass to your local
restauranteur), at depths below that of our bottom-moored instrument

Amid these and other distractions, a fair amount of useful work was
accomplished. Accounting during the past week included 21 CTDO/LADCP/
rosette stations, 8 TMC casts, 6 ice sampling stations, 4 moorings
set and 1584 km of ship track swath-mapped. Phaeocystis was found to
dominate the high biomass in the Amundsen Polynya, but DMS was lower
there than in PIB and dissolved iron was low except below 100 m near
the ice shelves. A CRREL Ice Mass Balance buoy was installed near the
ITP, and is now reporting local surface conditions, according to
Lamont weatherman Richard Cullather.

RPS and ECO support has been exemplary, along with that of our
mooring maestros..

1 comment:

  1. Too bad you can't fish for some Patagonia toothfish, even though it's on the Do Not Eat list. A dinner of fresh fish would be pretty rewarding!