Friday, 23 March 2018

Tropical palaeoclimate progress meeting in a Siberian blast…by guest blogger Heather Moorhouse

The DeepCHALLA UK group plus Principal Lead Investigator Dirk
Verschuren (University of Ghent) in cool Cambridge.
Scientists braved the “beast from the east” to attend the DeepCHALLA progress meeting of the UK NERC-funded collaborators at the University of Cambridge, UK. DeepCHALLA is an International Continental scientific Drilling Program project, involving researchers from across the globe who are investigating ~250,000 years of climate and environmental change in equatorial east Africa. This work is centered on investigating different biological, chemical and physical properties of sediments retrieved from the depths of Lake Challa, located on the Kenyan/Tanzanian border, on the lower eastern flanks of the iconic Mount Kilamanjaro.

Lucky to have avoided many of the travel disruptions, we huddled in the warmth of the University of Cambridge School of Geography to discuss our preliminary findings on the sediment samples taken last July as part of the subsampling party at the University of Ghent (see previous blog). Excellent progress is being made in using tephra (volcanic ash), palaeomagnetic signals and carbon-dating which will help produce a well-resolved chronology of the sediment record. This is often one of the main constraints when interpreting environmental history over long timescales, so it is great to have confidence in when key changes in the record occurred. There was also exciting findings on historical volcanic activity, influences of climate on biological communities in the lake and the role of humans vs. climate on fire regimes, which can be an important driver of terrestrial biodiversity change.


SEM image of diatoms from the sediments of Lake Challa.
These are diatoms of the species Nitzschia.
At Lancaster University, we have been working alongside colleagues at BGS to investigate the sources and nature of carbon in the organic matter of the sediments, as well as the oxygen and carbon isotopes used and stored in the silica cell walls of diatoms, a dominant group of algae in Lake Challa (see previous blog). We are particularly interested in how carbon cycling and lake primary productivity was modified by the severe aridity of the megadroughts, which occurred around 130 to 90 thousand years ago.   This work is still very much a work in progress, but we have exciting preliminary findings in reference to the megadrought period. As we collect more data, we look forward to working with others on the project in order to develop unique insights into the environmental history of equatorial east Africa.

The next stages for me involve more laboratory preparation of diatom samples, a return to Ghent to collect more sediment to analyse and organizing outreach activities in Kenya and Tanzania. But more pressing is keeping warm, and thinking of tropical climes amidst the icy blast which continues to wreak havoc on much of the UK.

Heather is a post doctoral research assistant on the NERC funded grant (between Lancaster, BGS, Cambridge, Belfast, SUERC) based at Lancaster University.

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