Final Report Summary - ICEPROXY (Novel Lipid Biomarkers from Polar Ice: Climatic and Ecological Applications.)
Over the past few years, considerable attention has been given to the acute changes in ice cover of the Earth’s Polar Regions. This decline is of particular concern since sea ice is a critical component of the climate system by its major contribution to Polar oceanic or atmospheric processes. In addition, with the acute changes in sea ice cover observed for both Polar Regions in recent years, there is a critical need to investigate how such rapid changes will impact on polar ecosystems. We have recently developed a new sea ice proxy allowing for a rapid acquisition of high-resolution sea ice data. The basis of the proxy is a group of lipid biomarkers which, as well as being unique to sea ice diatoms, are resistant to degradation and sufficiently abundant in the environment to be measured with a high degree of geological resolution.
The ICEPROXY project involved a combination of rigorous quantifications and calibrations of these new markers in sediments collected across the Arctic and the Antarctic in order to provide high-resolution sea ice datasets for at least the last 10,000 years. During the five years of the project, ICEPROXY team members were involved in several fieldtrips to Polar Regions and obtained a comprehensive set of samples, including sea ice, phytoplankton, sediments and a large set of polar organisms.
While, analysis of Arctic and Antarctic samples further confirmed the specific origin of these biomarkers and their resistance to degradation in the sediments, the comparison of biomarker concentrations with historical or other proxy data provided regional calibrations and new information about historical sea ice variations from key regions of the Arctic and the Antarctic. For example, we have generated a 30,000 years record of sea ice conditions in the Fram Strait, a major gateway to the Arctic Ocean. This reconstruction showed that, although perennial sea ice prevailed during most of the last glacial maximum, this region experienced an abrupt warming some 14,000 year ago with ice-free conditions during the summer. Shortly after, the region experienced a dramatic cooling with the return to a permanent sea-ice cover affecting not only primary production but also higher trophic levels and resulting in a widespread ecological decline. Similarly, high-resolution analyses of a sediment archive from the North Icelandic shelf revealed that abrupt changes in surface oceanic conditions occurred over the last millennium and that these changes resulted from large tropical volcanic eruptions. Our observations, combined with model results, showed that a sequence of eruptions resulted in a large ocean cooling followed by warmer and nearly ice-free conditions due to a subsurface heat build-up.
In Antarctica, we collected a large set of sediment cores on the Adélie Land Shelf, a region where large amounts of sea ice are formed during the winter and, according to the recent literature, contributes to nearly 30% of the Antarctic Bottom Waters. In 2010, a giant iceberg was calved by the Mertz glacier inducing profound changes to the surface oceanic conditions. In the absence of this natural barrier, large amounts of sea ice are advected in the area. While deeply reducing local sea ice production and the contribution of the area to global oceanic circulation, heavy ice conditions in the area also have a profound impact on local ecosystems. A multi-proxy analysis of the sediments collected by the ICEPROXY project team revealed that these massive calving events were recurrent during the last centuries (following an 80 to 90 years cyclicity) and that these events were always accompanied by an increase in sea ice concentration/duration and a strong decrease of the dense water formation. We also show that the recent intensification of the Southern Annular Mode (attributed to anthropogenic ozone depletion) further contributes to establishing icier conditions in the area. At the same time, the analysis of several biological samples collected in the area revealed that all of the species investigated (including top predators such as birds and seals) were relying on sea ice primary productivity for their development. In particular, the analysis of the tissues and eggs of Antarctic birds (Adélie penguin, Snow petrel) revealed a close relationship between sea ice, concentration of lipid biomarkers and their breeding success.
The ICEPROXY project involved a combination of rigorous quantifications and calibrations of these new markers in sediments collected across the Arctic and the Antarctic in order to provide high-resolution sea ice datasets for at least the last 10,000 years. During the five years of the project, ICEPROXY team members were involved in several fieldtrips to Polar Regions and obtained a comprehensive set of samples, including sea ice, phytoplankton, sediments and a large set of polar organisms.
While, analysis of Arctic and Antarctic samples further confirmed the specific origin of these biomarkers and their resistance to degradation in the sediments, the comparison of biomarker concentrations with historical or other proxy data provided regional calibrations and new information about historical sea ice variations from key regions of the Arctic and the Antarctic. For example, we have generated a 30,000 years record of sea ice conditions in the Fram Strait, a major gateway to the Arctic Ocean. This reconstruction showed that, although perennial sea ice prevailed during most of the last glacial maximum, this region experienced an abrupt warming some 14,000 year ago with ice-free conditions during the summer. Shortly after, the region experienced a dramatic cooling with the return to a permanent sea-ice cover affecting not only primary production but also higher trophic levels and resulting in a widespread ecological decline. Similarly, high-resolution analyses of a sediment archive from the North Icelandic shelf revealed that abrupt changes in surface oceanic conditions occurred over the last millennium and that these changes resulted from large tropical volcanic eruptions. Our observations, combined with model results, showed that a sequence of eruptions resulted in a large ocean cooling followed by warmer and nearly ice-free conditions due to a subsurface heat build-up.
In Antarctica, we collected a large set of sediment cores on the Adélie Land Shelf, a region where large amounts of sea ice are formed during the winter and, according to the recent literature, contributes to nearly 30% of the Antarctic Bottom Waters. In 2010, a giant iceberg was calved by the Mertz glacier inducing profound changes to the surface oceanic conditions. In the absence of this natural barrier, large amounts of sea ice are advected in the area. While deeply reducing local sea ice production and the contribution of the area to global oceanic circulation, heavy ice conditions in the area also have a profound impact on local ecosystems. A multi-proxy analysis of the sediments collected by the ICEPROXY project team revealed that these massive calving events were recurrent during the last centuries (following an 80 to 90 years cyclicity) and that these events were always accompanied by an increase in sea ice concentration/duration and a strong decrease of the dense water formation. We also show that the recent intensification of the Southern Annular Mode (attributed to anthropogenic ozone depletion) further contributes to establishing icier conditions in the area. At the same time, the analysis of several biological samples collected in the area revealed that all of the species investigated (including top predators such as birds and seals) were relying on sea ice primary productivity for their development. In particular, the analysis of the tissues and eggs of Antarctic birds (Adélie penguin, Snow petrel) revealed a close relationship between sea ice, concentration of lipid biomarkers and their breeding success.