Faculty candidate seminar - Xingchen (Tony) Wang

04/05/2018 - 1:00pm
Eckart Lecture Hall room 227
Event Description: 


DATE:          April 5th, Thursday, 1 p.m.  

LOCATION:     Eckart Lecture Hall
SPEAKER:      Xingchen (Tony) Wang, Ph.D.
            California Institute of Technology

TITLE:  Coral as a new archive of the marine N cycle: From the ice age to the Anthropocene


Nitrogen (N) is a key element of life and limits primary productivity in much of the ocean. The status of biologically available (or fixed) N in the ocean has implications for such properties as the amounts of CO2 and O2 in the atmosphere. Natural variation in the ratio of the two stable N isotopes (15N and 14N) is a power tracer of the marine N cycle, both today and in the past. In this talk, I will introduce a novel tool for studying the ocean’s N cycle: N isotopes of organic matter bound within the annually banded carbonate skeletons of corals. This measurement has been applied to address two questions in marine biogeochemistry. In the first application, the N isotopes of Southern Ocean deep-sea fossil corals indicate the entire Southern Ocean, both Antarctic and Subantarctic Zones, was nutrient-depleted during the last ice age relative to modern conditions, supporting the hypothesis that Southern Ocean changes contributed to the lower atmospheric CO2 concentration of the ice ages. In the second application, N isotope records from offshore Bermuda and South China Sea were used to assess the impact of anthropogenic N deposition on the open Ocean in the Anthropocene. While the measurements showed that the west Pacific has already been clearly affected by anthropogenic N deposition, the North Atlantic shows no signs of anthropogenic influence as yet, instead apparently recording the decadal signal of the North Atlantic Oscillation. These data indicate a weaker influence of anthropogenic N on the open ocean than had been suggested by models. 

Faculty Host:  Andreas Andersson  (aandersson@ucsd.edu)
For more information on this event, contact: 
Event Calendar: