Project: NSFGEO-NERC: Collaborative Research: Accelerating Thwaites Ecosystem Impacts for the Southern Ocean (ARTEMIS)

NSF abstract:

Part I: Non-technical summary:
The Amundsen Sea is adjacent to the West Antarctic Ice Sheet (WAIS) and hosts the most productive coastal ecosystem in all of Antarctica, with vibrant green waters visible from space and an atmospheric carbon dioxide uptake rate ten times higher than the Southern Ocean average. The region is also an area highly impacted by climate change and glacier ice loss. Upwelling of warm deep water is causing melt under the ice sheet, which is contributing to sea level rise and added nutrient inputs to the region.

This is a project that is jointly funded by the National Science Foundation’s Directorate of Geosciences (NSF/GEO) and the National Environment Research Council (NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own country.

In this collaboration, the US team will undertake biogeochemical sampling alongside a UK-funded physical oceanographic program to evaluate the contribution of micronutrients such as iron from glacial meltwater to ecosystem productivity and carbon cycling. Measurements will be incorporated into computer simulations to examine ecosystem responses to further glacial melting. Results will help predict future impacts on the region and determine whether the climate sensitivity of the Amundsen Sea ecosystem represents the front line of processes generalizable to the greater Antarctic. This study is aligned with the large International Thwaites Glacier Collaboration (ITGC) and will make data available to the full scientific community. The program will provide training for undergraduate, graduate, post-doctoral, and early-career scientists in both science and communication. The team will also develop out-of-school science experiences for middle and high schoolers related to climate change and Antarctica.

Part II: Technical summary:
The Amundsen Sea hosts the most productive polynya in all of Antarctica, with atmospheric carbon dioxide uptake rates ten times higher than the Southern Ocean average. The region is vulnerable to climate change, experiencing rapid losses in sea ice, a changing icescape and some of the fastest melting glaciers flowing from the West Antarctic Ice Sheet, a process being studied by the International Thwaites Glacier Collaboration. The biogeochemical composition of the outflow from the glaciers surrounding the Amundsen Sea is largely unstudied. In collaboration with a UK-funded physical oceanographic program, ARTEMIS is using shipboard sampling for trace metals, carbonate system, nutrients, organic matter, and microorganisms, with biogeochemical sensors on autonomous vehicles to gather data needed to understand the impact of the melting ice sheet on both the coastal ecosystem and the regional carbon cycle. These measurements, along with access to the advanced physical oceanographic measurements will allow this team to 1) bridge the gap between biogeochemistry and physics by adding estimates of fluxes and transport of limiting micronutrients; 2) provide biogeochemical context to broaden understanding of the global significance of ocean-ice shelf interactions; 3) determine processes and scales of variability in micronutrient supply that drive the ten-fold increase in carbon dioxide uptake, and 4) identify small-scale processes key to iron and carbon cycling using optimized field sampling. Observations will be integrated into an ocean model to enhance predictive capabilities of regional ocean function.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Project metadata and links to related datasets in project ARTEMIS are available from USDAP-DC site:  https://www.usap-dc.org/view/project/p0010249

NERC Award Abstract: 
The Amundsen Sea hosts the most productive polynya in coastal Antarctica, with its vibrant green waters visible from space, and an atmospheric CO2 uptake flux density 10x higher than average for the Southern Ocean. The region is vulnerable to climate change, with rapid losses in sea ice, episodic shifts in the coastal icescape, and the fastest melting glaciers in the adjacent West Antarctic Ice Sheet (WAIS). In an ecosystem experiencing such dramatic change, it is critical to resolve the climate-sensitive drivers and feedbacks of the meltwater-associated iron (Fe) delivery, which underpins productivity in this otherwise high-nutrient, low chlorophyll region. Our previous field research (ASPIRE) identified a clear link between the melting WAIS and the delivery of micronutrient Fe to the polynya ecosystem, and its role in rapid CO2 drawdown. Our recent numerical modeling effort (INSPIRE) suggests several pathways for Fe delivery, ways to optimize fieldwork, and guidance for improving mechanistic understanding of Fe supply and cycling. An ongoing physical oceanographic field program (TARSAN, part of the International Thwaites Glacier Collaboration, ITGC) offers an ideal physical framework for our next research effort. We propose here to collaborate with TARSAN-supported UK scientists, providing significant value added to both teams. TARSAN explored the eastern Amundsen Sea by ship in Feb-Mar 2019 and expects to operate in the Thwaites region again in Feb-Mar 2021. They will use a full suite of physical oceanographic techniques, including 2 under-ice-shelf AUVs, gliders, surface vehicles, a microstructure profiler, shipboard CTD, seal tags, noble gases, and underway sensors to characterize the ice-ocean interactions responsible for rapid glacial melting. During 2019, TARSAN and THOR (also ITGC) collected detailed bathymetric, sedimentary, and ice-shelf cavity information (available Sept 2019) that will immediately improve and update the INSPIRE model to present-day boundary conditions. Our combined NSFGEO-NERC project (ARTEMIS) will facilitate collaboration between ASPIRE/INSPIRE team members and TARSAN/ITGC, add biogeochemical measurements to the funded 2021 expedition, and build on existing glider infrastructure and seal tag expertise (adding biogeochemical sensors to autonomous vehicles) at modest additional logistical cost. Numerical runs with ARTEMIS's updated model will inform TARZAN's 2021 field effort. Observations made will improve our understanding and our model, allowing a more sophisticated assessment of the role of Fe in present and future scenarios. Our team (ARTEMIS) would add shipboard biogeochemical observations (trace metals, carbonate system, nutrients, organic matter, microorganisms) and autonomous vehicle biogeochemical observations (nitrate, Chl a, optical backscatter) to gather knowledge critical to understanding the impact of WAIS melting on both the polynya ecosystem and the regional carbon (C) cycle. ARTEMIS combines the expertise of a US component comprising a carbonate system and microbial ecologist (Yager), a trace metal biogeochemist (Sherrell), a trace metal isotope geochemist (Fitzsimmons), an organic geochemist (Medeiros), an ice-ocean-atmosphere interactions expert (Stammerjohn), and a numerical ocean modeler (St-Laurent), with a UK component comprising 3 physical oceanographers: TARSAN lead PI (Heywood), a biogeochemically savvy autonomous vehicle expert (Queste), and an oceanographer whose vehicles are marine mammals (Boehme). This international team will work together at sea and with shore-based analyses to address a set of interconnected questions arising from the findings of ASPIRE/ INSPIRE.