miércoles, 31 de octubre de 2012

Thousands of Meters Below The Ice.

For those that don't know neither me nor the blog, I will take advantage that I wrote this post for the blog of the GEO journal and of the institute where I work (AWI blog), and I will present myself again. 

My name is Raquel Somavilla and I’m an oceanographer. I work at the Alfred Wegener Institute (AWI) since one year ago, and I live in Bremerhaven although I’m Spanish. I’m studying at AWI the deep water masses of the Arctic Ocean and the Greenland Sea. Maybe it doesn’t sound very exciting, but don’t trust in the appearances.

Why should we care about the deep water masses of the Arctic? Well, most of you probably know about the high vulnerability of the Arctic to climate change due to among other reasons the big changes in sea surface temperature or ice cover that are taking place here. However, the importance of the Arctic not only resides in the surface. Few things are known about the changes that could be taking place in the deep waters (until 5000 m. depth), because for a long time the deep Arctic Ocean has been considered imperturbable to the remaining changes observed in the surface.

Besides, in the Arctic Ocean and Greenland Sea, deep water formation takes place. This is a very important process for our climate, because these waters that sink to the bottom are substituted by warner waters coming from southern latitudes at the surface. Without these movements of warm waters at the surface from the Equator to the Polar Regions, and cold waters at the bottom from the Poles to the Equatorial regions, the low latitudes would become warmer and warmer, and the high latitudes colder and colder. This is one of the ways in which the deep Arctic Ocean and Greenland Sea contribute to the regulation of our climate, and for this reason the changes in their deep water masses are very important.  What are the causes of these changes? Well, the changes in the deep water masses of the Arctic and the Greenland Sea have the origin in processes thousands of meters above and thousands of kilometers away. It will take me a little while to explain how, but if you read until the end you will understand.

Fig. 1. Map of the Arctic Ocean and Greenland Sea and temperature and salinity measurements in these ocean basins (see text below for further explanation). (Source: Raquel Somavilla).

In Fig. 1, I show you a map of the Arctic Ocean and the Greenland Sea including temperature and salinity data measured in these ocean basins (To know how we measure temperature and salinity in the ocean you can read this previous post). In the map you also see a white arrow. It represents an important current entering the Greenland Sea from further south in the Atlantic; then, in the Arctic Ocean through Fram Strait; and flowing all around the Arctic until its exit again through Fram Strait towards the North Atlantic. The maximum representation of this current is the flow of Atlantic water that you can identify all along the Arctic through a subsurface temperature and salinity maximum (they are the shadow areas that I mark you in the temperature and salinity vertical profiles in Fig. 1 b and c).

What does this picture tell us about the Greenland Sea and the Arctic Ocean? The main feature of the Greenland Sea that we can infer from Fig. 1b and c is that temperature and salinity are quite homogenous from the surface to the bottom (4000 m.) in comparison with the Arctic Ocean. It is the result of a process known as open ocean convection which is a very effective mechanism of mixing due to the strong cooling during the winter months. Why is the water column in the Arctic Ocean different? Because in the Arctic the presence of the ice and fresh water in the surface enhances the stability of the upper layer and deep convection, as occurs in the Greenland Sea, cannot take place. What more things do you notice in Fig. 1? I suppose that the presence of warmer and saltier waters in the deep Arctic Ocean, further north than the Greenland Sea, could result an odd feature. What are the reasons for that? I explain below, but first I need to leave you another figure. Look at it while you read the next paragraph. 

Fig. 2 Processes of deep water formation in the Arctic Ocean. (Source: Raquel Somavilla, AWI).

During the winter, very, very low air temperatures occur in the Arctic. The sea surface temperature decreases until the freezing point and ice formation takes place. The ice cannot incorporate the salt present in the sea water, and so when the ice is formed the salt leaves the ice increasing the salinity and density of the surface waters. The ice formation mainly takes place on the Arctic shelves. From there, these denser waters created on the shelves (plumes) will deepen in the water column until its density equals that of the waters at the same depth. Similar to a snow ball, the volume of the plumes increases as they ‘fall’ down the slope, because they incorporate ambient water in their descent, as the scheme in Fig. 2 shows. To understand how this works, we can imagine a black snow ball falling down a white mountain. As it descends, its volume increases getting lighter, and lighter grey, because it takes white snow from the mountain, while the mountain also results darker. The water that our ‘snow ball’ takes from the mountain (slope) belongs to the flow of Atlantic water that we already know. We also have seen that the Atlantic flow transports warm and salty water. Thus, our ‘snow balls’ falling along the slope in the Arctic take part of the heat and salt in the Atlantic layer and transport it to deeper levels. It explains why as we move into the Arctic Ocean following the white arrow in Fig. 1 (dots pass from pink to dark red in the map and in Fig. 1b and c) the deeper waters become warmer and saltier while the Atlantic flow becomes colder and fresher.  

So, I hope now you understand why the origin of the deep waters in the Arctic and Greenland Sea is in surface processes; in water that comes from southern latitudes in the Atlantic; and that any change that they provoke in the deep waters of the Arctic and Greenland Sea will have the potential to affect our climate.  I find the understanding of the physical mechanisms linking all these processes at different compartments in the ocean climate really exciting, and I feel lucky that my research may contribute to it.  

However, we didn't take only measurements of the deep water masses of the Arctic during our cruise. We did a lot of things. In previous posts you have more information about that. Below, you have some nice pictures of our cruise in the Arctic. I know sometimes they are the best part of a post ;-). I hope you like it. 

(Source: Raquel Somavilla, AWI)
(Source: Raquel Somavilla, AWI)

domingo, 21 de octubre de 2012

Back to the office

Después de dos meses y medio de campana, viviendo en un barco donde cada día te levantas sin tener que pensar demasiado en que tienes que hacer, porque básicamente lo que tienes que hacer es hacer tus guardias, tomar tus medidas, etc., la vuelta al trabajo lleva al menos un par de días de adaptación. Además de los datos que hayamos podido recopilar, no nos vamos con todo el trabajo anterior terminado, y hay cosas que retomar y terminar. Así que, de repente te ves con un montón de cosas por hacer y no sabes por donde empezar. Se pierde la costumbre. Yo intento organizarme haciendo una lista con todas esas cosas, a poder ser por orden de prioridad. La lista ya está completa y hasta he conseguido tachar alguna de las tareas que he apuntado en ella.

After a cruise of two months and a half of duration, living on board a research ship where each morning you wake up without the necessity of thinking what you have to do this day, because basically you only have to do your job: e.g. your watch and take your measurements, the return to the office requires at least a pair of days of adaptation. Besides the data that we have collected during the cruise, we don’t start the cruise with all the previous work done, and so when you return there are a lot of things to pick up and finish. Thus, suddenly, you have a lot of things to do, and you don’t know where to start. Good habits can be quickly lost. I try to organize myself again doing a list of things to do, if possible ordered by priority. My list is complete now, and I have already crossed out some of the tasks that I annotated on it.

Mi cuaderno de notas en la terraza de la cafetería del AWI (esta semana está haciendo genial). Lo llevo conmigo a todos lados para no olvidarme de nada
My notebook in the terrace of the AWI Cafeteria (this week the weather is being great). I take it with me always to not forget anything. Source: Raquel Somavilla

Pensaréis que casi una semana es mucho tiempo para reincorporarse al ritmo de trabajo, pero es que además la vuelta al mundo real también implica vuelta al mundo en … INTERNET!!!!! Llegas y tienes un montón de correos, un montón de links con cosas interesantes que te apetece leer, y todo eso sólo hace que te sea difícil concentrarte en el resto de tareas en tu lista. En casa he podido entrar al blog y responder comentarios J; compartir las fotos de la campana en Facebook y tener noticias de mis amigos; hablar por skipe con  mi familia; y encontrar un montón de cosas interesantes que otra gente también comparte. Aquí abajo os dejo algunas de las cosas que he visitado estos días.

You can think that almost one week is too long to go back to the rhythm of daily work, but the return to the ‘real world’ also implies the return to the world in …INTERNET!!! As soon as you arrive, you have a lot of mails, a lot of links with intriguing stuffs that you would like to read, and that only hinder you to concentrate in the remaining tasks in your list. At home, I have been able to access to the blog and answer your comments J; share photographs from the cruise on Facebook and have news from my friends; talk by Skipe with my family; and to find a lot of other interesting things that people share in internet. Below, I leave some of those things that I have visited during these days.

Un par de blogs / A pair of blogs:

Este primero ya lo conocía pero hacía mucho que no podía visitarlo.
The first I already knew, but it’s been a long time since the last time I could visit it.

El segundo es nuevo. Me ha gustado mucho este post, así que os dejo el link.
The second is new. I liked a lot this post, and so here I share with you the link.

Más cosas. En la siguiente página web hay revisiones de artículos y claras explicaciones de lo que la ciencia dice sobre algunos mitos relacionados con el clima. Un ejemplo: ‘El clima ha sufrido variaciones naturales anteriormente’. Es cierto, pero tras esa frase muchas veces pretenden a veces respaldar la idea de que ello implica que nosotros no estamos contribuyendo al resto de cambios que hoy día observamos. En el link que os dejo explican de manera brillante que tal conclusión es simplemente errónea. Que haya habido variaciones naturales no implica que estas no puedan ser forzadas antropogénicamente. ¿Por qué? Pues porque la pregunta clave a responder no es si son naturales o antropogénicas sino cual es la causa de las variaciones de nuestro clima. Anteriormente no han ocurrido mágicamente, sino en momentos en los que nuestro clima ha sufrido un desajuste, es decir, en momentos en que hemos recibido más calor del que hemos devuelto a la atmósfera y la temperatura aumentó; o, al revés, hemos recibido menos calor del que hemos liberado y la temperatura del planeta disminuyó. Las causas naturales son diversas como variaciones en la energía recibida del Sol -no siempre es la misma-, o emisiones volcánicas que emiten partículas a la atmósfera que reflejan parte de la radiación solar y hacen que el planeta se enfríe. A día de hoy el aumento de la concentración de gases invernadero hace que acumulemos calor y que aumente la temperatura. En resumen: ‘El Clima reacciona a cualquier forzamiento que lo haga cambiar con el tiempo, y nosotros provocamos actualmente el mayor de ellos’. Con esto no quiero decir que lo que hoy observamos sea únicamente consecuencia de nuestras actividades, pero por supuesto contribuimos.

More things. In the following web site, there are very good reviews of scientific papers and clear explanations of what Science says about some 'climate myths', e.g. ‘Climate’s changed before’. I don’t translate the rest of the previous paragraph for English speakers, because that information is very well explained in the link, but if you have any question I will be glad to answer them.

Sobre herramientas de trabajo. Como otros utilizan Photoshop o AutoCad, los oceanógrafos utilizamos Matlab para trabajar. La pega de Matlab es que es muy caro. Yo no tengo que pagar la licencia que utilizo en el trabajo, pero utilizar un software libre para hacer tu trabajo es siempre una gran ventaja. Así que esta semana, cuando una amiga del AWI (Kathrin) me planteo que estaba pensando en aprender Python, le sugerí rápidamente que lo hiciésemos juntas. Ya hemos empezado. Aquí abajo os dejo un link de un libro sobre Python para aplicaciones en mi campo, pero se pueden hacer muchas otras cosas con él y hay más libros disponibles. De momento, sólo hemos llegado hasta el capítulo 3 pero promete. Os contaré más, si al final resulta tan bueno como parece.

About working tools. As others use Photoshop or AutoCad, oceanographers use Matlab. The drawback of Matlab is that it is very expensive. I don’t have to pay the license that I use for my work -AWI does that for me-, but using free software to do your job can be always a big advantage. So, the last week, when a friend, which works with me at AWI, told me that she was thinking to start learning Python, I quickly suggested her that we could do it together. We have already started. Below, I leave a link of a book about the use of Python in ocean and atmospheric sciences, but you can do much more things with Python, and there are more books available. For the moment, we haven’t passed from chapter 3, but it seems promising. I tell you more about it, if finally it is as good as it seems.

Una actualización de última hora: Como os decía el domingo cuando escribí el post se pueden hacer muchas más cosas con Python (pinchad aquí). Sobre sus aplicaciones en ciencia (oceanografía, meteorología, biología, etc) también tengo un nuevo enlace. Y es que nuestro 'grupo de estudio' ha aumentado a 5 personas, y claro 5 personas piensan y encuentran más cosas que 2 ;-).

A last minute update: As I told you on Sunday, when I wrote this post, you can do a lot of things with Python (click here). About its applications in Science (oceanography, meteorology, biology, ...), I also have a new link to show you (now here). Our 'study group' has increased in number of members, we are 5 now, and, of course, 5 persons think and find more things than 2 ;-).

Espero que alguno de ellos os guste o resulte útil. Todavía tengo un montón de fotos de la campaña para compartir con vosotros, así que tenéis una más.

I hope you like or you find useful some of them. I still have plenty photos from my cruise in the Arctic to share with you, so here you have another one.

Svalbard. Source: Raquel Somavilla