How do ice ages happen? Exploring paleosalinity and thermohaline circulation

Fill a glass of water from the sea and try to drink it. You gag and your lips pucker. After all, dissolved in that liter of the ocean are around 35 grams of salt. Now, imagine you tried to do this same thing 1 million years ago, 10 million years ago, 100 million years ago, even 500 million years ago. Would you ever be able to drink the water — or would it ever be as salty as the Dead Sea today? These are the questions that investigating paleosalinity helps us answer. We can use a variety of methods — from rough estimates based on our knowledge of the earth system to direct evidence from water droplets preserved in old rocks — to determine how salty the ocean was throughout Earth’s history.

Figuring out how ocean salinity has changed is important not simply because it helps us fill pages in our history book. Changing salinity affects ocean circulation, which in turn has a huge impact on climate. For instance, recent studies have suggested that changes in thermohaline circulation are part of how the Earth cycles between glacial and interglacial periods. In other words, ocean circulation may be the missing link between orbital variations that we know are linked to the cycle of ice ages and the huge swings in CO2 and temperature that are directly responsible for plunging us into glacial periods. In short, tracing paleosalinity helps us understand just how the Earth’s temperature can change so drastically.

This paper is therefore driven by the question: How can paleosalinity help us understand climatic variation, especially that caused by changes in thermohaline circulation? To begin to answer this question, I will present two methods of determining paleosalinity: first, by making an inventory of evaporites; and second, by looking at fluid inclusions. I then turn to the effects that these changes in salinity have on climate, especially by looking at models of how thermohaline circulation would differ and past cases where similar things occurred (for instance, in the Younger Dryas).

Continue reading How do ice ages happen? Exploring paleosalinity and thermohaline circulation

The Life of a Hat from Luzon

A version of this object biography was published in the Spring 2019 issue of Contexts: Annual Report of the Haffenreffer Museum of Anthropology.

This hat is a product of — produced by and traded through — colonialism. Its resting place today is the Haffenreffer Museum of Anthropology in Providence, Rhode Island in the United States of America. There it lies mostly undisturbed; whether dormant or dead is hard to tell. But it was once part of daily life. The hat shielded its owner from the sun and from hazards both natural and man-made. It was also a handy bowl when flipped upside down — quite literally a vessel for life, though even this framing underestimates the hat’s vitality. After all, it has a nose, eyes, and an ear, not to mention some impressive hair. It is more of a head than a hat, in fact. There is something particularly compelling to telling the life story of such an object — from its beginnings in the early twentieth century in Ifugao, a province of Luzon (an island in the Philippines); to its “collection” by an American official in 1912–14; to its acquisition by the Haffenreffer at an auction in 1988.

Say you were to reinvigorate the object. Pick it up (it’s so light!); turn it upside down; feel the contours on the bottom of the bowl; drag your thumb across the tightly woven rattan brim; note how the light glistens off what seems like its polished metal exterior. When you’re done with the physiognomy, try moving your head closer and breathing in. The smell of the wood can’t help but evoke memories, fantasies, even disturbing thoughts. After all, its military past is ingrained in the pores of the wood and the basketry of its brim. What has the hat seen? What has it heard, touched, smelled?

Continue reading The Life of a Hat from Luzon

How salty has the sea been over the past 541 million years?

Take a bottle of water from the sea and try to drink it. You gag and your lips pucker. After all, dissolved in that liter of the ocean are around 35 grams of salts (mostly sodium chloride). Now, imagine you tried to do this same thing 1 million years ago, 10 million years ago, 100 million years ago, even 500 million years ago (that is, throughout the Phanerozoic eon). Would you ever be able to drink the water? Alternatively, would the sea ever have been so salty that today’s ocean creatures would not have survived? A 2006 article by Hay et al. helps answer precisely these questions. The authors tracked variable chloride levels to demonstrate how salinity has changed throughout the Phanerozoic, noting a significant overall decline. These changes have had important effects on ocean circulation and on plankton levels — and possibly contributed to the explosion of complex life in the Cambrian, 541–520 million years ago. Continue reading How salty has the sea been over the past 541 million years?

My Independent Concentration

I recently found out that my proposal for an independent concentration in Critical Thought and Global Social Inquiry has been approved! Just what does this mean, and why am I so happy about it?

First of all, a few words on what an independent concentration is (at Brown). Apart from the standard concentrations (majors) we offer, every student has the opportunity to design their own course of study. This concentration proposal must be reviewed and approved by a subcommittee of the College Curriculum Council, the same body that approves regular concentrations. The process of proposing an IC is supervised by the Curricular Resource Center, which has multiple peer student staffers who meet regularly with students who want to create an IC. The actual proposal is long and rigorous. Furthermore, the committee almost as a rule rejects first-time applications; there is a heavy emphasis on the process of proposing an IC as a conversation between the committee and the student with the aim being to create a well-articulated, coherent, and rigorous course of study that aligns with Brown’s wider educational goals. I personally found this process extremely rewarding: it helped me process my interests and a few thoughts that had been rolling around in my head (many because of courses I had taken). I am now much more articulate about these interests and I have a much better idea of how they align with my broader life goals. Although the process of creating an IC is arduous, for me it was well worth it.

To explain what my Independent Concentration is about, here’s an excerpt from my proposal (which you can find in full here):

What is Critical Thought and Global Social Inquiry? It is the study of global social phenomena such as postcolonialism, nationalism, and global justice through the philosophical lens of critical theory. I think dialectically about both the institutions derived from the Enlightenment and the practices, communities, and identities developed and deployed in resistance to these institutions. I am thus equally invested in studying the universal and metropolitan on the one hand and the particular and peripheral on the other. As a field of study, I imagine my Independent Concentration as a conversation with a number of figures invested in this dialectic – chief among them Edward Said, Hannah Arendt, and Cornel West. In many ways, this field of study is constituted by its intellectual genealogy: while investigating questions about how societies cohere, how politics functions, and how the past shapes our present (and drawing on sources from many times and places), what distinguishes Critical Thought and Global Social Inquiry is its distinctive perspective. This reflexive, provisional approach is gathered from the theoretical consciousness developed through the philosophical tradition of critique. Given my commitment to provisionality and reflexivity, I do not intend through this concentration to provide conclusive answers to the questions I described above. The fundamental aim of Critical Thought and Global Social Inquiry is instead to develop concrete questions, modes of interpretation, and resources for action that resonate across different commitments and backgrounds. Through my concentration, I develop a map – a way to navigate the incredible diversity of thought and experience our world has to offer.

Working with Women’s Refugee Care

In Fall 2017, I was fortunate enough to take an engaged course in the French department called L’expérience des réfugiés et immigrés (The Experience of Refugees and Immigrants). This course was developed last summer and offered for the first time this year (see article for more). It combined a survey of Francophone texts by and about migration with an engaged component: working with Women’s Refugee Care (WRC). My French improved because I got the chance to use it in a setting with no safety net: in the community engagement portion of the course, French really was the best means of communication. More importantly, this course was a great opportunity to get involved with a local nonprofit and explore the idea of engaged scholarship (which I’m continuing to do through the Engaged Scholars Program in Archaeology).

My work with Women’s Refugee Care centered on three interviews I did with members of the Congolese refugee community here in Providence. Along with Jeanelle Wheeler, my wonderful colleague, we got to know the community, attending a few gatherings and meeting lots of interesting people. We then arranged interviews with a few of those we met at their homes. After recording the interviews, we translated them into English and then posted them on the WRC blog.

I’m particularly happy with the final result: interviews with Katerina, Aline, and Sylvie. I encourage you to read what they have to say — not just to admire their successes and appreciate the challenges they faced, but to acknowledge them as multifaceted human beings. I also wrote an introduction to the interviews (in French), where I reflect on the entire experience, including obstacles, challenges, and the path we took in presenting them as we did. If you find this interesting or stimulating, I would love to know — just add a comment here or send me an email.1