ECV-Ice: Measuring Essential Climate Variables in Sea Ice-SCOR Working Group 152

Observations over recent decades suggest that sea ice plays a significant role in global biogeochemical cycles, providing an active biogeochemical interface at the ocean-atmosphere boundary. However, a pressing need exists to perform methodological intercalibration experiments in order to obtain reliable measurements of basic biogeochemical properties, including many of the Essential Climate Variables of the Global ClimateObserving System. With newly emerging techniques, and pressed by the rapid changes in sea ice, the time has come to evaluate and improve our approach to study sea-ice systems. In 2016, the Scientific Committee on Oceanic Research (SCOR) launched Working Group 152 on Measuring Essential Climate Variables in Sea Ice (ECV-Ice). This working group will synthesize past intercalibration exercises and design and coordinate new experiments. Our ultimate goal is to provide the international community with standardized protocols forprocessing sea-ice samples and collecting data for key variables, including CO2 partial pressure, nutrients, algal biomass and production, and gas exchange. We will also establish the effectiveness of new techniques to address sea-ice heterogeneity (often referred to as “patchiness”). These tasks will directly benefit the longterm community goal of understanding the response of polar marine environments to ongoing climate change.0info:eu-repo/semantics/publishe

Further observations of a decreasing atmospheric CO2 uptake capacity in the Canada Basin (Arctic Ocean) due to sea ice loss

Using data collected in 2009, we evaluated the potential for the southeastern Canada Basin (Arctic Ocean) to act as an atmospheric CO₂ sink under the summertime ice-free conditions expected in the near future. Beneath a heavily decayed ice cover, we found surprisingly high pCO₂sw (~290–320 µatm), considering that surface water temperatures were low and the influence of ice melt was strong. A simple model simulating melt of the remaining ice and exposure of the surface water for 100 days revealed a weak capacity for atmospheric CO₂ uptake (mean flux: −2.4 mmol m⁻² d⁻¹), due largely to warming of the shallow mixed layer. Our results confirm a previous finding that the Canada Basin is not a significant sink of atmospheric CO₂ under summertime ice-free conditions and that increased ventilation of the surface mixed layer due to sea ice loss is weakening the sink even further

BEPSII Arctic Policy Brief

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ECV-ice: Measuring Essential Climate Variables in Sea Ice – SCOR Working Group 152

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The role of sea ice in the carbon cycle of polar oceans

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Hydroclimatic controls on the isotopic (δ¹⁸ O, δ² H, d-excess) traits of pan-Arctic summer rainfall events

Abstract Arctic sea-ice loss is emblematic of an amplified Arctic water cycle and has critical feedback implications for global climate. Stable isotopes (δ¹⁸O, δ²H, d-excess) are valuable tracers for constraining water cycle and climate processes through space and time. Yet, the paucity of well-resolved Arctic isotope data preclude an empirically derived understanding of the hydrologic changes occurring today, in the deep (geologic) past, and in the future. To address this knowledge gap, the Pan-Arctic Precipitation Isotope Network (PAPIN) was established in 2018 to coordinate precipitation sampling at 19 stations across key tundra, subarctic, maritime, and continental climate zones. Here, we present a first assessment of rainfall samples collected in summer 2018 (n = 281) and combine new isotope and meteorological data with sea ice observations, reanalysis data, and model simulations. Data collectively establish a summer Arctic Meteoric Water Line where δ²H = 7.6⋅δ¹⁸O–1.8 (r² = 0.96, p < 0.01). Mean amount-weighted δ¹⁸O, δ²H, and d-excess values were −12.3, −93.5, and 4.9‰, respectively, with the lowest summer mean δ¹⁸O value observed in northwest Greenland (−19.9‰) and the highest in Iceland (−7.3‰). Southern Alaska recorded the lowest mean d-excess (−8.2%) and northern Russia the highest (9.9‰). We identify a range of δ¹⁸O-temperature coefficients from 0.31‰/°C (Alaska) to 0.93‰/°C (Russia). The steepest regression slopes (>0.75‰/°C) were observed at continental sites, while statistically significant temperature relations were generally absent at coastal stations. Model outputs indicate that 68% of the summer precipitating air masses were transported into the Arctic from mid-latitudes and were characterized by relatively high δ¹⁸O values. Yet 32% of precipitation events, characterized by lower δ¹⁸O and high d-excess values, derived from northerly air masses transported from the Arctic Ocean and/or its marginal seas, highlighting key emergent oceanic moisture sources as sea ice cover declines. Resolving these processes across broader spatial-temporal scales is an ongoing research priority, and will be key to quantifying the past, present, and future feedbacks of an amplified Arctic water cycle on the global climate system