Homeward Bound

We’ve been transiting north towards Punta Arenas, Chile for several days now. After exchanging some personnel and gear at Palmer Station on Anvers Island we passed through the Gerlache Strait and into the Drake Passage. We were extremely fortunate to have favorable seas on both our transit south toward Antarctica and again heading north. (The Drake Passage can have some of the roughest seas in the world!)

A 180° view of the Gerlache Strait

We’ve noticed much warmer air temperatures and more sea birds since reaching the tip of South America. Soon we’ll turn into the Straits of Magellan and we are hoping to spend our last day at sea observing dolphins, penguins, and whales before the hectic off-load and long flights home begin.

As we near the Argentinian coastline we’ve spotted quite a few fishing and re-supply vessels like the one above

This afternoon we held a “science symposium” where the leader of each research group shared some of their team’s more interesting findings from the previous month. The photos and vast quantity of data were remarkable, but what struck me the most was how all of our research – physics, microbiology, macrobiology, and chemistry – fits so well together to tell a “big picture” story about the changes that are occurring on the Western Antarctic Peninsula as our climate changes. The LTER (Long Term Ecological Research) Program is one of the more unique scientific endeavors that the US supports; normally research studies are only 1 – 3 years in the field. Having 20+ years of interdisciplinary field data is rare; having it in one of the most rapidly changing climate systems on Earth is priceless. Let’s hope funding for this type of vital research that helps us understand food webs, sea level changes, ocean circulation, and climate change continues for many years to come.


~ This is the final post for the Southern Ocean 2015 blog - thanks for reading along! ~

February 3, 2015

Most groups on board study things that are visible to the naked eye – whales, penguins, plankton, etc. These creatures are all part of the marine food web, and at the base is phytoplankton – the very small algae that photosynthesize. In addition to light, these plankton need carbon, nitrogen, phosphorus and a bunch of other elements in very small quantities to grow. Among these essential elements is iron (Fe). Iron is such a scarce nutrient that it can actually limit the growth of phytoplankton in some marine areas – including the Western Antarctic Peninsula. Because iron and many other elements (mercury, lead, zinc, etc.) occur in such small quantities we call them “trace” elements.

Trace elements are interesting because they can help us figure out why phytoplankton grown in certain areas but not others. Some of them can also help us figure out where they are coming from – dust blown over from South America and Australia, the weathering (“decay”) of the Antarctic continent, the melting of glaciers, or ocean currents which move south from lower latitudes.

In order to study these trace elements from a ship made of metal (inside and out!) many precautions are required to avoid contaminating seawater samples. These include using special metal-free collection bottles and a make-shift cleanroom made from wooden framing and plastic sheeting.

Rob Sherrell (Rutgers U., foreground) leads a deployment of the surface water sampler

Jess Fitzsimmons (Rutgers U.) sampling surface water, plumbed from the sampler off the side of the ship into the make-shift clean room

The “trace elements” team prepares the water collection bottles for a cast into the ocean

Ice

One of the more dangerous hazards to Antarctic explorers/oceanographers is ice. Its behavior is highly dependent on the wind which can either hold it together loosely or pack it in very tightly so that when the temperature drops, the ice freezes together and ships get stuck. This happened to Ernest Shackleton in the earlier 1900s and continues to happen to vessels as recently as last year. Our science questions only bring us about 2 km beyond the ice edge, and the Captain keeps a watchful eye on the wind and temperature in case we need to get out quickly. No need to worry, Mom!

As we approached the Wilkins Ice Shelf we found a surreal amount of ice.

Loosely packed sea ice as far as the eye can see

Lots of wildlife on the ice – including a Crabeater seal in the foreground and some penguins in the background; the horizon is almost impossible to see with the snowy-white sky

Ice is extremely strong and destructive, so it must be kept away from the equipment. Here our Antartctic Support Crew memebers Lindsey Loughry (L) and Hannah Gray (R) use boat hooks to keep ice away from the CTD and its wire.

Some of the ice floes are larger and can support the seals, some are enormous icebergs (very far distance), and a lot of it reminds me of Slurpee from 7-11.

2 curious Crabeater seals watch our ship pass by – I wonder what they think of our giant orange ship??? Most seals watch us bump through the ice instead of scooting away or hiding below the ice.

Plants of the Sea

Today we finished the 3rd of our “process stations” which are aimed at getting a more in-depth understanding of what influences the living creatures in the ocean at various locations. Some of the most abundant and most important sea creatures are phytoplankton. They are the tiny (microscopic!) photosynthetic plants that live in our seawater and form the base of the oceanic food web: phytoplankton are eaten by zooplankton such as krill, who are in turn eaten by fish, whales and penguins.

Oscar Schofield (Rutgers U.) and his team are on board to understand both the distribution of these phytoplankton and what controls their growth. There are many types of plankton, and light levels are one of the ways they differentiate their niches.  At each station his group sends optical sensors into the upper water column to collect data on light absorption and scattering, which is used to identify who is living where. By calibrating these measurements against satellites in space, we hope future satellite data can be used to predict phytoplankton community composition. We already use satellites to measure sea surface temperature and phytoplankton quantity – but being able to tell more about which types are there will help us make better predictions about the rest of the food web.

Oscar Schofield and his student Filipa Carvalho collecting seawater.

In addition to the optical sensors, more traditional methods of measuring phytoplankton are employed. This involves collecting seawater and passing it through very small (45 µm) filters. These filters are then analyzed back on land for both the quantity of phytoplankton and which species are present.

Left: Unused filter, Right: After 500 mL of seawater were filtered. Although the phytoplankton are too small to see in the seawater, here we can clearly see many diatoms are present (identified by their greenish-brown color).

Besides light, nutrient availability and grazers (zooplankton) also control phytoplankton growth. If there aren’t enough nutrients (i.e., food) like iron or nitrogen in the water not very many phytoplankton can grow. In contrast if zooplankton out number phytoplankton then they will be eaten as quickly as they can grow, keeping the population small. To understand which of these factors is most important in controlling phytoplankton blooms (large population spurts), graduate student Filipa Carvalho is doing incubation experiments that vary light, iron and grazer concentrations in clear bottles.

Recent doctoral graduate Mansha Seth-Pasricha and grad student Filipa begin an incubation experiment.

On this trip we only have time to stop at ~30 stations to collect data, so the Schofield group also has “gliders” which fill in the big gaps between these locations. The gliders are autonomous underwater vehicles (AUVs) which look like yellow torpedoes. They swim through the water, diving between the surface and several hundred meters depth. The gliders collect data on the current, salinity, temperature, oxygen levels, and biomass throughout the West Antarctic peninsula’s underwater shelf and then report it back electronically. Many oceanographers see AUVs as the future of oceanography because they can go out and collect large quantities of data for you to process from the comfort of your office. How convenient!

Under Pressure

Since leaving Rothera Station we scientists have been busy in our laboratories. Our ship is zig-zagging on and off shore to the west of the Antarctica Peninsula, stopping at pre-determined locations to collect water and plankton samples. Some of these stations are located above the continental shelf – a stretch of underwater land that is about 300 meters (~ 950 feet) deep. This shelf has numerous features where it gets deeper (troughs and canyons) which influence how the water moves, where plankton live, and bigger picture things like where whales go to eat. When we continue to move off-shore the shelf drops off and the seafloor is ~ 3,000 meters (~ 2 miles). That’s ten times deeper!

Imagine diving down to the bottom of the deep end in a swimming pool. One of the most noticeable feelings is that your ears begin to hurt. This is due to the pressure of ~ 5 meters of water above you. The scientific equipment we send down to collect data about the water (temperature, salinity, oxygen content, etc.) has to be specially built to withstand extremely high pressures – way more than what you could withstand. One way to visualize the pressure is to send down a piece of Styrofoam. Those of us on the ship who feel artistically inclined (… and some of us who don’t) have been decorating cups to attach to our equipment and send down 3,000 meters. Below are two photos of my cups: before and after. As you can see, the pressure compacts the Styrofoam quite a bit

Before

After

Rothera

Yesterday morning we arrived at Rothera Station on Adelaide Island. Most of the scientists on the Gould got off of the ship so that ~30 British scientists from the island could go aboard and do a half day of science around the island. While they were busy at sea, the rest of us were split into groups and taken on various activities by our British hosts. Some people went skiing and snowboarding, others did a strenuous hike followed by crevassing, and the rest took a nature walk around Rothera Point to see the bay and its wildlife. The weather was phenomenal: very sunny, blue skies and in the 30s °F. After our activities, the ship returned and we ate dinner together followed by music from 3 different bands that the British have formed for the summer season.

 Jack Conroy on the nature walk

 

Watching a plane land on the airstrip; planes are used to do aerial surveys (e.g., for whales) and also transport researchers to more remote field camps
  

An Adelie penguin jumps out of the water to look at us

 

A Weddell seal swimming around in the bay

 

A pile of sleeping elephant seals; they like to sun themselves on the rocky shore for warmth
 

A 180° view from the point. Directly across the water you can see the Antarctic Peninsula!

 

Jess Fitzsimmons and Filipa Carvalho (both Rutgers U.) inside a crevasse. The crevasse (a deep crack in a glacier) appears blue due to the light shining through the ice and snow from above (photo courtesy of Jess Fitzsimmons)

TGIF

Happy Friday! Because ship time is very expensive, we don’t (normally) get weekends here. In fact, operations are 24 hours a day, 7 days a week. However, most of us will get a day off tomorrow when we arrive at Rothera Station on Adelaide Island. This research station is the headquarters of British Antarctic research, and they will graciously host us for a few meals, outdoor activities, and traditional soccer match. After our 24 hour stop it will be back to work!

Today has been very crisp and clear. As we get closer to the Antarctic continent and islands we’re passing more and more icebergs. The scenery is phenomenal!

A small part of Adelaide Island

The very bright sun and some icebergs