We Blogged It!
December 30, 2010
On the way to Pine Island Bay to recover moorings
I don’t think the ASPIRE Team could have asked for a better ending to the old year. By all accounts the overwhelming feeling is of success rooted in synergy- strong teamwork between scientists, support teams and the crew.
After their meeting with the Oden, the team turned their attention to the prime objectives of ASPIRE: investigating the climate-sensitive processes driving the productivity and carbon sequestration of the Amundsen Sea polynya.
Sampling has included four "long" (18h) process stations where multiple CTD casts (TMC and conventional) were deployed, in situ pumps, numerous net tows (including a mid-day and a mid-night MOCNESS), and sediment grabs. These stations are meant for intensive experimental and process studies and they intend to complete 6 of them, 1 about every 3 days, over the course of their time in the polynya.
Although ice conditions cut a planned 72 hr deployment of the drifting sediment traps short, they were still able to collect large amounts of material from depths of 60m, 150m, and 300m. They plan to repeat this at another process station later this week.
Daily stations measure core biological and chemical inventories and rates mid-day in the context of the water column profile. In the evenings, they set out on transects designed to clarify the physical and geochemical context for process and daily stations.
Chief Tish reports: “We stop every 10-12 nm to collect a depth profile with the CTD sensors, sampling water for chemistry on about every other cast. These late-evening excursions have proven to be extremely valuable for mapping the quantity and extent of the bloom. The ship's underway sampling system is set up to measure temperature, salinity, fluorescence, pCO2, and O2 continuously, so (with the assistance of Povl Abrahamsen from the Jacobs team) we have been able to generate a beautiful map of the bloom's spatial extent.”(see image)
“We have thus completed 25 TMC-CTD profiles and 65 conventional CTD profiles at 50 stations. The pace of this work has been possible only with the much-appreciated assistance of the mooring team (Raul Guerrero and Povl Abrahamsen). We have also completed 4 sets of day-night MOCNESS tows and 11 in situ pump deployments. Strong and responsive RPS support has also made this level of effort possible.”
She adds: “Preliminary results reveal that the phytoplankton bloom in the Amundsen Sea polynya exceeds all expectations, being greater even than the reported "big bloom" of Feb 2009. “ This algal bloom is a mix of Phaeocystis with some diatoms.” Surface pCO2 concentrations reveal high levels of net community production and carbon flux. And despite 24 hours of sunlight, day-night differences have been observed in the zooplankton populations.
“Also, more zooplankton was found at the deep trough station (1000 m) than on the shallower (500 m) shelf. Fish and shrimp larvae were particularly abundant in the marginal ice zone, but no crab larvae have been observed so far. Material from the first trap station on the shelf suggests that the bloom is sinking out primarily as phytoplankton aggregates. Whether this changes as we move into deeper waters (where zooplankton were more abundant) remains to be determined at one of the remaining process stations.”
The glider (deployed on Dec 15) completed a profiling of 330km over 13 days. The data from its deployment confirms the high chlorophyll levels in the central polynya and gave the team information that they would have missed using only the ship’s underway system. They expect a short redeployment in the final days in the polynya.
The team is now trying to break into the ice in Pine Island Bay to recover the remaining moorings. However, ice conditions are causing them to re-assess their route and game plan. Once the moorings are recovered they will return to the polynya for two final long stations. They expect to leave the polynya region around Jan 8-9.
Tish concludes with: ”… we are well meeting and perhaps even exceeding our expectations. Equipment glitches have been fairly minor and science support from both the ship and RPS has been absolutely outstanding. I have been particularly impressed by the RPS and ship's ability to deploy and recover the drifting sediment trap and glider under very difficult conditions. I continue to be inspired by the hard-working and talented team of people on this expedition, including the scientists, the ship's captain and crew, and the RPS support. They work together well, and have risen to meet every challenge to generate a truly extraordinary data set from this poorly understood but important ecosystem."
Happy New Year! With warmest wishes, Tish”
And Lollie ☺
Question of the Day
- What are Polynyas and why are they important to study?
Polynyas, are recurring areas of seasonally open water surrounded by ice.
Energy and material transfer between the atmosphere, polar surface ocean, and the deep sea in polynas provide polar ecosystems with just the right ingredients needed for high productivity and intense biogeochemical recycling.
Polynyas may be the key to understanding the future of Polar Regions since their extent is expected to increase with anthropogenic warming.