13 research outputs found
Impact of sea ice on air-sea CO2 exchange – A critical review of polar eddy covariance studies
Sparse in situ measurements and poor understanding of the impact of sea ice on air-sea gas exchange introduce
large uncertainties to models of polar oceanic carbon uptake. The eddy covariance technique can be used to
produce insightful air-sea gas exchange datasets in the presence of sea ice, but results differ between studies. We
present a critical review of historical polar eddy covariance studies and can identify only five that present
comparable flux datasets. Assessment of ancillary datasets, including sea-ice coverage and type and air-sea
concentration gradient of carbon dioxide, used to interpret flux datasets (with a specific focus on their role in
estimating and interpreting sea ice zone gas transfer velocities) identifies that standardised methodologies to
characterise the flux footprint would be beneficial. In heterogeneous ice environments both ancillary data un�certainties and controls on gas exchange are notably complex. To address the poor understanding, we highlight
how future efforts should focus on the collection of robust gas flux datasets within heterogeneous sea ice regions
during key seasonal processes alongside consistent ancillary data with a full characterisation of their associated
uncertainties
Methods for biogeochemical studies of sea ice: The state of the art, caveats, and recommendations
AbstractOver the past two decades, with recognition that the ocean’s sea-ice cover is neither insensitive to climate change nor a barrier to light and matter, research in sea-ice biogeochemistry has accelerated significantly, bringing together a multi-disciplinary community from a variety of fields. This disciplinary diversity has contributed a wide range of methodological techniques and approaches to sea-ice studies, complicating comparisons of the results and the development of conceptual and numerical models to describe the important biogeochemical processes occurring in sea ice. Almost all chemical elements, compounds, and biogeochemical processes relevant to Earth system science are measured in sea ice, with published methods available for determining biomass, pigments, net community production, primary production, bacterial activity, macronutrients, numerous natural and anthropogenic organic compounds, trace elements, reactive and inert gases, sulfur species, the carbon dioxide system parameters, stable isotopes, and water-ice-atmosphere fluxes of gases, liquids, and solids. For most of these measurements, multiple sampling and processing techniques are available, but to date there has been little intercomparison or intercalibration between methods. In addition, researchers collect different types of ancillary data and document their samples differently, further confounding comparisons between studies. These problems are compounded by the heterogeneity of sea ice, in which even adjacent cores can have dramatically different biogeochemical compositions. We recommend that, in future investigations, researchers design their programs based on nested sampling patterns, collect a core suite of ancillary measurements, and employ a standard approach for sample identification and documentation. In addition, intercalibration exercises are most critically needed for measurements of biomass, primary production, nutrients, dissolved and particulate organic matter (including exopolymers), the CO2 system, air-ice gas fluxes, and aerosol production. We also encourage the development of in situ probes robust enough for long-term deployment in sea ice, particularly for biological parameters, the CO2 system, and other gases.This manuscript is a product of SCOR working group 140 on Biogeochemical Exchange Processes at Sea-Ice Interfaces
(BEPSII); we thank BEPSII chairs Jacqueline Stefels and Nadja Steiner and SCOR executive director Ed Urban for their
practical and moral support of this endeavour. This manuscript was first conceived at an EU COST Action 735 workshop
held in Amsterdam in April 2011; in addition to COST 735, we thank the other participants of the “methods” break-out
group at that meeting, namely Gerhard Dieckmann, Christoph Garbe, and Claire Hughes. Our editors, Steve Ackley and
Jody Deming, and our reviewers, Mats Granskog and two anonymous reviewers, provided invaluable advice that not only
identified and helped fill in some gaps, but also suggested additional ways to make what is by nature a rather dry subject
(methods) at least a bit more interesting and accessible. We also thank the librarians at the Institute of Ocean Sciences for
their unflagging efforts to track down the more obscure references we required. Finally, and most importantly, we thank
everyone who has braved the unknown and made the new measurements that have helped build sea-ice biogeochemistry
into the robust and exciting field it has become.This is the final published article, originally published in Elementa: Science of the Anthropocene, 3: 000038, doi: 10.12952/journal.elementa.00003
Recommended from our members
Methods for biogeochemical studies of sea ice: The state of the art, caveats, and recommendations
Over the past two decades, with recognition that the ocean's sea-ice cover is neither insensitive to climate change nor a barrier to light and matter, research in sea-ice biogeochemistry has accelerated significantly, bringing together a multi-disciplinary community from a variety of fields. This disciplinary diversity has contributed a wide range of methodological techniques and approaches to sea-ice studies, complicating comparisons of the results and the development of conceptual and numerical models to describe the important biogeochemical processes occurring in sea ice. Almost all chemical elements, compounds, and biogeochemical processes relevant to Earth system science are measured in sea ice, with published methods available for determiningbiomass, pigments, net community production, primary production, bacterial activity, macronutrients, numerous natural and anthropogenic organic compounds, trace elements, reactive and inert gases, sulfur species, the carbon dioxide system parameters, stable isotopes, and water-ice-Atmosphere fluxes of gases, liquids, and solids. For most of these measurements, multiple sampling and processing techniques are available, but to date there has been little intercomparison or intercalibration between methods. In addition, researchers collect different types of ancillary data and document their samples differently, further confounding comparisons between studies. These problems are compounded by the heterogeneity of sea ice, in which even adjacent cores can have dramatically different biogeochemical compositions. We recommend that, in future investigations, researchers design their programs based on nested sampling patterns, collect a core suite of ancillary measurements, and employ a standard approach for sample identification and documentation. In addition, intercalibration exercises are most critically needed for measurements of biomass, primary production, nutrients, dissolved and particulate organic matter (including exopolymers), the CO2 system, air-ice gas fluxes, and aerosol production. We also encourage the development of in situ probes robust enough for long-Term deployment in sea ice, particularly for biological parameters, the CO2 system, and other gases
The impact of lower sea-ice extent on Arctic greenhouse-gas exchange
In September 2012, Arctic sea-ice extent plummeted to a new record low: two times lower than the 1979-2000 average. Often, record lows in sea-ice cover are hailed as an example of climate change impacts in the Arctic. Less apparent, however, are the implications of reduced sea-ice cover in the Arctic Ocean for marine-atmosphere CO2 exchange. Sea-ice decline has been connected to increasing air temperatures at high latitudes. Temperature is a key controlling factor in the terrestrial exchange of CO2 and methane, and therefore the greenhouse-gas balance of the Arctic. Despite the large potential for feedbacks, many studies do not connect the diminishing sea-ice extent with changes in the interaction of the marine and terrestrial Arctic with the atmosphere. In this Review, we assess how current understanding of the Arctic Ocean and high-latitude ecosystems can be used to predict the impact of a lower sea-ice cover on Arctic greenhouse-gas exchange