We are moving steadily southwestward at about 10kt. The last 3 days have been clear, sunny and calm, although temps are around freezing. Today is a return to more typical Southern Ocean weather. Winds are out of the north at 25-30kt and the sea is up to about 5 feet. It is a "beam sea" with waves coming towards the side of the boat. If the waves get bigger, it will cause the boat to "roll" (move side-to-side) which can be an uncomfortable ride. For the moment, the waves are too small to move the boat very much. The sky is overcast and there are snow flurries (and we are in the "summer" hemisphere--have you seen snow yet?).
We are almost across the Antarctic Circumpolar Current (ACC). The dashed red line on the map is the southern boundary of the ACC. Once we are out of the ACC, we will be in the Ross Gyre, which is a large circular (clockwise) flow that fills the Ross Sea. Technically, we will be in the Ross Sea but it will be a few more days before we will start making measurements. A few of us are meeting today to consider the location of sea ice (which we can see from satellite images) and decide where we want to go first. It won't be too long before we will be crunching through some of the residual sea ice. As you might imagine, we can not move as fast in sea ice so we want to avoid it as much as possible.
The Ross Sea is "odd" because in the spring the sea ice (frozen sea water) opens up from south to north. This process forms the Ross seasonal polynya (a Russian word that means "an area of open water when the air is cold enough for the ocean to freeze"). In the spring when the ice starts to loosen a bit, strong winds from the south (off the Antarctic continent) blow the ice to the north opening the polynya. After a while there is a big arc of sea ice along the northern part of the Ross Sea. Eventually, most of this ice moves to the north (where it is a bit warmer) and melts. We need to get through the east side of this sea ice arc to get to our sampling area. It should be loose pack ice but it means that we will need to maneuver to avoid the larger or thicker floes. Sea ice is typically only a few feet thick in contrast to icebergs (which is made of compressed snow) which can be hundreds of feet thick.
Yesterday, while the sea conditions were mild, we used the VPR (video plankton recorder) to look at the plankton (small drifting plants and animals). This device is a flying body with a variety of sensors for temperature, salinity, chlorophyll and others. The body is programmed to move up and down in the water while the ship moves. It covers the top 100 m (330 ft) of the ocean. Its main purpose is to measure small floating organisms. It does so by illuminating a small volume (1 cubic centimeter--about 1/3 inch on a side) with a laser and capturing a digital picture. Software sorts through this 3-d image to pick out anything in focus. "Interesting" parts of the image are saved for someone to identify.
(The VPR sitting on the aft deck waiting to be deployed over the stern.)
This device photographs about 20 volumes a minute. It has been out for about a day. A little multiplication produces a large number of images to evaluate. Since these are high resolution images, saving them requires a lot of disk space.
One result from these measurements is that there is considerable variation in the plankton density indicating eddies (swirling water) in the ocean that hold concentrations of plankton in their center. One purpose of our cruise is to find and study such eddies. We are also measuring water flow so we can see the swirling flow along with the concentrated plankton.
There are several rituals in the maritime world that are observed on research vessels. One is "crossing lines" in which crossing certain latitudes or longitudes is thought worthy of a celebration. We crossed the Antarctic Circle (67 33.3 S) on January 2. As part of the celebration, "King Neptune" appears on the boat and charges those who are crossing for the first time (polywogs) with various crimes against King Neptune. These crimes cause the polywogs to be "cleaned" which involves splashing or spraying with water. The "royal court" is made of those who have been "cleaned" on previous trips. All first crossers are issued a fancy certificate signed by the ship's captain to testify to their crossing. This allows them to be "excused" from future crossing ceremonies.
(King Neptune and his court.)
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