Position: 35°43N / 24°21W
You can follow the rout on www.ipev.fr – position des naires Marion Dufresne
Dear fellow Teachers,
Tonight we are still travelling towards the Azores. We had a rainy morning with wind about 50km an hour (ca 27 Nts). But now the beautiful sun is shining again. We have a place we call the “beach” in front of the ship. There we find especially the Scandinavians soaked in sunoil and sunrays! In their defense, they come from the rainiest city in Norway and therefore need to store vitamin-D for the wintertime. Since there is no work today, most people are busy writing emails and reports, or just resting.
The sediment on the ocean floor represents layers of geological history. Therefore, if we can sample a vertical slice of this sediment, we will be able to obtain information about conditions during previous time periods. This information will allow us to make connections between past, present, and future climate and circulation patterns. This is extremely important to understand the current warming trend within the context of other interglacial, or warming periods.
Casq coring system
Casq coring system
It takes a lot of work and sophisticated equipment to take a “slice,” or a core, of sediment. We use the Calypso coring system to acquire longer cores (maximum of about 60 meters). These longer cores are important to study more distant time periods. We are taking two other types of cores: Casq (or calypso squared) cores, and multi-cores. The Casq core is not as long as the Calypso core, but it provides undisturbed sediments. How much time is represented in a core depends on sedimentation rate and the length of the core. The multi-core is even shorter than the Casq core, however, it provides even greater detail about the surface layers of sediment. Also, the multi-corecovers a larger lateral area, and so gives us information about lateral variation of the sediment. We will discuss the equipment involved in more detail in a subsequent entry.
Calypso coring system
Calypso coring system
There are many factors that must be taken into account when choosing coring sites. First, we use echosounding to determine the depth, the topography of the sea floor, and the characteristics of the layers of sediment. The ship has electric engines because they are quiet, and will not interfere with the echosounding technology. Also this type of engine allows the ship to remain stable during the coring operation.
Echosounding profile
Even though some sampling sites are pre-determined, it takes hours to find the site and position the ship. If the ship is moving coring is impossible. The topography at the sites must be flat and at the apex of a dome-shaped peak (so the sample is not contaminated by slipping sediment). The area must have enough parallel sediment layers to be sampled, and the sediments must be of a certain type (the area cannot be too rocky).
Our first core off the coast off Morocco was about 40 meters long. It was a bit bent due to the trigger not functioning properly. We were, however, able to process the sample, and the information will be very useful in reconstructing conditions during past interglacial periods. Now that we have one Casq core, one multi-core, and three Calypso cores from our first two sites, we are ready to process the samples!
Processing a core
In a later email we will detail some of the work that goes into processing and storing these samples. Since this is an interdisciplinary endeavor we will be able to detail many applications of chemistry, physics, geology, oceanography, climatology and biology, which we hope you will share with your students.
Your sailor team Teachers at Sea!
Sem comentários:
Enviar um comentário