scholarly journals Widespread surface water pCO2 undersaturation during ice-melt season in an Arctic continental shelf sea (Hudson Bay, Canada)

Elem Sci Anth ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Mohamed M. M. Ahmed ◽  
Brent G. T. Else ◽  
Brian Butterworth ◽  
David W. Capelle ◽  
Céline Guéguen ◽  
...  
Keyword(s):  
Sea Ice ◽  
Co2 Flux ◽  
Early Summer ◽  
The Arctic ◽  
Spatial And Temporal Variability ◽  
Hudson Bay ◽  
Co2 Fluxes ◽  
Arctic Seas ◽  
Co2 Partial Pressure ◽  
Ice Melt

Estimating sea–air CO2 fluxes in coastal seas remains a source of uncertainty in global carbon budgets because processes like primary production, upwelling, water mixing, and freshwater inputs produce high spatial and temporal variability of CO2 partial pressure (pCO2). As a result, improving our pCO2 baseline observations in these regions is important, especially in sub-Arctic and Arctic seas that are experiencing strong impacts of climate change. Here, we show the patterns and main processes controlling seawater pCO2 and sea–air CO2 fluxes in Hudson Bay during the 2018 spring and early summer seasons. We observed spatially limited pCO2 supersaturation (relative to the atmosphere) near river mouths and beneath sea ice and widespread undersaturated pCO2 in offshore and ice-melt-influenced waters. pCO2 was highly correlated with salinity and temperature, with a limited but statistically significant relationship with chlorophyll a and fluorescent dissolved organic matter. Hudson Bay on average was undersaturated with respect to atmospheric CO2, which we attribute mainly to the dominance of sea-ice meltwater. We calculated an average net CO2 flux of about –5mmol CO2 m–2 day–1 (–3.3 Tg C) during the spring and early summer seasons (92 days). Combining this result with extrapolated estimates for late summer and fall seasons, we estimate the annual CO2 flux of Hudson Bay during the open water season (184 days) to be –7.2 Tg C. Our findings indicate that the bay on average is a weaker CO2 sink than most other Arctic seas, emphasizing the importance of properly accounting for seasonal variability in the Arctic coastal shelves to obtain reliable sea–air CO2 exchange budgets.

scholarly journals Underestimation of surface pCO2 and air-sea CO2 fluxes due to freshwater stratification in an Arctic shelf sea, Hudson Bay

Elem Sci Anth ◽  
2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Mohamed M. M. Ahmed ◽  
Brent G. T. Else ◽  
David Capelle ◽  
Lisa A. Miller ◽  
Tim Papakyriakou
Keyword(s):  
Sea Ice ◽  
River Runoff ◽  
Dissolved Inorganic Carbon ◽  
Stable Isotope Ratio ◽  
Total Alkalinity ◽  
Hudson Bay ◽  
Co2 Fluxes ◽  
Ancillary Data ◽  
Ice Melt ◽  
The Impact

The objective of this study is to quantify the impact of freshwater stratification on the vertical gradients of partial pressure of CO2 (pCO2) and estimates of air-sea CO2 exchange in Hudson Bay during peak sea-ice melt and river runoff. During the spring of 2018, we sampled water in Hudson Bay and Hudson Strait for dissolved inorganic carbon, total alkalinity, salinity, the oxygen stable isotope ratio in the water (δ18O), and other ancillary data. The coastal domain and regions close to the ice edge had significant vertical concentration gradients of pCO2 across the top meters of the ocean due to the presence of a stratified fresh layer at the surface. The pCO2 and salinity in the central (where sea-ice melt was significant) and the southeast (where river runoff and sea-ice melt were significant) side of the bay generally increased with depth, with average gradients of 4.5 μatm m–1 and 0.5 m–1, respectively. Ignoring these gradients causes a significant error in calculating air-sea CO2 fluxes, especially when using shipboard underway systems that measure pCO2 at several meters below the sea surface. We found that the oceanic CO2 sink in Hudson Bay is underestimated by approximately 50% if underway pCO2 system measurements are used without correction. However, we observed that these gradients do not persist for more than 5 weeks following ice melt. We have derived a linear correction for underway pCO2 measurements to account for freshwater stratification during periods of 1–5 weeks after ice breakup. Given the lack of measurements in stratified Arctic waters, our results provide a road map to better estimates of the important role of these regions in global carbon cycles.

scholarly journals The thermodynamic state of the Arctic atmosphere observed by AIRS: comparisons during the record minimum sea-ice extents of 2007 and 2012

2013 ◽  
Vol 13 (1) ◽  
pp. 177-199 ◽  
Author(s):  
A. Devasthale ◽  
T. Koenigk ◽  
J. Sedlar ◽  
E. J. Fetzer
Keyword(s):  
Sea Ice ◽  
Circulation Pattern ◽  
Early Spring ◽  
Early Summer ◽  
The Arctic ◽  
Sea Ice Extent ◽  
Atlantic Sector ◽  
Thermodynamic State ◽  
Ice Melt ◽  
Arctic Atmosphere

Abstract. The record sea-ice minimum (SIM) extents observed during the summers of 2007 and 2012 in the Arctic are stark evidence of accelerated sea ice loss during the last decade. Improving our understanding of the Arctic atmosphere and accurate quantification of its characteristics becomes ever more crucial, not least to improve predictions of such extreme events in the future. In this context, the Atmospheric Infrared Sounder (AIRS) instrument onboard NASA's Aqua satellite provides crucial insights due to its ability to provide 3-D information on atmospheric thermodynamics. Here, we facilitate comparisons in the evolution of the thermodynamic state of the Arctic atmosphere during these two SIM events using a decade long AIRS observational record (2003–2012). It is shown that the meteorological conditions during 2012 were not extreme but three factors in preconditioning from winter through early summer probably played an important role in accelerating sea-ice melt. First, the marginal sea-ice zones along the central Eurasian and North Atlantic sectors remained warm throughout winter and early spring in 2012 preventing thicker ice build-up. Second, the circulation pattern favoured efficient sea-ice transport out of the Arctic in the Atlantic sector during late spring and early summer in 2012 compared to 2007. Third, additional warming over the Canadian Archipelago and southeast Beaufort Sea from May onward further contributed to accelerated sea-ice melt. All these factors may have lead already thin and declining sea-ice cover to pass below the previous sea-ice extent minimum of 2007. In sharp contrast to 2007, negative surface temperature anomalies and increased cloudiness were observed over the East Siberian and Chukchi Seas in the summer of 2012. The results suggest that satellite-based monitoring of atmospheric preconditioning could be a critical source of information in predicting extreme sea-ice melting events in the Arctic.

scholarly journals The Effect of Downwelling Longwave and Shortwave Radiation on Arctic Summer Sea Ice

2016 ◽  
Vol 29 (3) ◽  
pp. 1143-1159 ◽  
Author(s):  
Marie-Luise Kapsch ◽  
Rune Grand Graversen ◽  
Michael Tjernström ◽  
Richard Bintanja
Keyword(s):  
Sea Ice ◽  
Early Summer ◽  
Shortwave Radiation ◽  
The Arctic ◽  
Atmospheric Conditions ◽  
Sea Ice Extent ◽  
Climate Fluctuations ◽  
Ice Melt ◽  
Different Seasons ◽  
Arctic Summer

Abstract The Arctic summer sea ice has diminished fast in recent decades. A strong year-to-year variability on top of this trend indicates that sea ice is sensitive to short-term climate fluctuations. Previous studies show that anomalous atmospheric conditions over the Arctic during spring and summer affect ice melt and the September sea ice extent (SIE). These conditions are characterized by clouds, humidity, and heat anomalies that all affect downwelling shortwave (SWD) and longwave (LWD) radiation to the surface. In general, positive LWD anomalies are associated with cloudy and humid conditions, whereas positive anomalies of SWD appear under clear-sky conditions. Here the effect of realistic anomalies of LWD and SWD on summer sea ice is investigated by performing experiments with the Community Earth System Model. The SWD and LWD anomalies are studied separately and in combination for different seasons. It is found that positive LWD anomalies in spring and early summer have significant impact on the September SIE, whereas winter anomalies show only little effect. Positive anomalies in spring and early summer initiate an earlier melt onset, hereby triggering several feedback mechanisms that amplify melt during the succeeding months. Realistic positive SWD anomalies appear only important if they occur after the melt has started and the albedo is significantly reduced relative to winter conditions. Simulations where both positive LWD and negative SWD anomalies are implemented simultaneously, mimicking cloudy conditions, reveal that clouds during spring have a significant impact on summer sea ice while summer clouds have almost no effect.

scholarly journals The Potential of Space-Based Sea Surface Salinity on Monitoring the Hudson Bay Freshwater Cycle

2020 ◽  
Vol 12 (5) ◽  
pp. 873 ◽  
Author(s):  
Wenqing Tang ◽  
Simon H. Yueh ◽  
Daqing Yang ◽  
Ellie Mcleod ◽  
Alexander Fore ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Sea Ice ◽  
River Discharge ◽  
Open Water ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
The Arctic ◽  
Hudson Bay ◽  
Surface Salinity ◽  
Ice Melt

Hudson Bay (HB) is the largest semi-inland sea in the Northern Hemisphere, connecting with the Arctic Ocean through the Foxe Basin and the northern Atlantic Ocean through the Hudson Strait. HB is covered by ice and snow in winter, which completely melts in summer. For about six months each year, satellite remote sensing of sea surface salinity (SSS) is possible over open water. SSS links freshwater contributions from river discharge, sea ice melt/freeze, and surface precipitation/evaporation. Given the strategic importance of HB, SSS has great potential in monitoring the HB freshwater cycle and studying its relationship with climate change. However, SSS retrieved in polar regions (poleward of 50°) from currently operational space-based L-band microwave instruments has large uncertainty (~ 1 psu) mainly due to sensitivity degradation in cold water (<5°C) and sea ice contamination. This study analyzes SSS from NASA Soil Moisture Active and Passive (SMAP) and European Space Agency (ESA) Soil Moisture and Ocean Salinity(SMOS) missions in the context of HB freshwater contents. We found that the main source of the year-to-year SSS variability is sea ice melting, in particular, the onset time and places of ice melt in the first couple of months of open water season. The freshwater contribution from surface forcing P-E is smaller in magnitude comparing with sea ice contribution but lasts on longer time scale through the whole open water season. River discharge is comparable with P-E in magnitude but peaks before ice melt. The spatial and temporal variations of freshwater contents largely exceed the remote sensed SSS uncertainty. This fact justifies the use of remote sensed SSS for monitoring the HB freshwater cycle.

scholarly journals Energy- and mass-balance observations of the land–ice–ocean–atmosphere system near Barrow, Alaska, USA, November 1999–July 2002

2006 ◽  
Vol 44 ◽  
pp. 193-199 ◽  
Author(s):  
Thomas C. Grenfell ◽  
Donald K. Perovich ◽  
Hajo Eicken ◽  
Bonnie Light ◽  
Jeremy Harbeck ◽  
...  
Keyword(s):  
Sea Ice ◽  
Mass Balance ◽  
Early Summer ◽  
Shortwave Radiation ◽  
The Arctic ◽  
Lake Ice ◽  
Ice Melt ◽  
Detailed Surface ◽  
Coastal Sea ◽  
Land Surfaces

AbstractWe present results from a comprehensive field study carried out near Barrow, Alaska, USA, designed to characterize local- to intermediate-scale sea-ice processes in the Arctic coastal zone of central importance to the annual cycle and evolution of the coastal sea ice. Included in this are the behavior of the snow cover of the ice and adjacent tundra and lake system; concurrent studies of mass balance of the sea ice and lake ice; interaction of shortwave radiation with the shore-fast ice and the adjacent land surfaces; evolution of the area coverage and distribution of the various surface types; and the resulting regional albedo values. Maximum snow depths decreased during 2000–02 from 0.38 m to 0.26 m. Ice-melt rates in 2001 were 0.05 and 0.028md–1 at the top and bottom of the sea ice respectively, two to three times larger than observations from the central Arctic. Detailed surface results combined with aircraft photography were used to calculate regional albedos for the late spring and early summer of 2001. Values ranged from 0.8 for all cold snow-covered surfaces to approximately 0.4 for melting sea ice and lake ice vs 0.18 for bare tundra. Regional and surface-based values of cumulative shortwave radiation entering the ice were consistent, indicating that albedo sampling on a scale of 200m can provide a useful representation for regional sea-ice albedo.

scholarly journals The thermodynamic state of the Arctic atmosphere observed by AIRS: comparisons during the record minimum sea ice extents of 2007 and 2012

2013 ◽  
Vol 13 (15) ◽  
pp. 7441-7450 ◽  
Author(s):  
A. Devasthale ◽  
J. Sedlar ◽  
T. Koenigk ◽  
E. J. Fetzer
Keyword(s):  
Sea Ice ◽  
Circulation Pattern ◽  
Early Spring ◽  
Early Summer ◽  
The Arctic ◽  
Sea Ice Extent ◽  
Atlantic Sector ◽  
Thermodynamic State ◽  
Ice Melt ◽  
Arctic Atmosphere

Abstract. The record sea ice minimum (SIM) extents observed during the summers of 2007 and 2012 in the Arctic are stark evidence of accelerated sea ice loss during the last decade. Improving our understanding of the Arctic atmosphere and accurate quantification of its characteristics becomes ever more crucial, not least to improve predictions of such extreme events in the future. In this context, the Atmospheric Infrared Sounder (AIRS) instrument onboard NASA's Aqua satellite provides crucial insights due to its ability to provide 3-D information on atmospheric thermodynamics. Here, we facilitate comparisons in the evolution of the thermodynamic state of the Arctic atmosphere during these two SIM events using a decade-long AIRS observational record (2003–2012). It is shown that the meteorological conditions during 2012 were not extreme, but three factors of preconditioning from winter through early summer played an important role in accelerating sea ice melt. First, the marginal sea ice zones along the central Eurasian and North Atlantic sectors remained warm throughout winter and early spring in 2012 preventing thicker ice build-up. Second, the circulation pattern favoured efficient sea ice transport out of the Arctic in the Atlantic sector during late spring and early summer in 2012 compared to 2007. Third, additional warming over the Canadian archipelago and southeast Beaufort Sea from May onward further contributed to accelerated sea ice melt. All these factors may have lead the already thin and declining sea ice cover to pass below the previous sea ice extent minimum of 2007. In sharp contrast to 2007, negative surface temperature anomalies and increased cloudiness were observed over the East Siberian and Chukchi seas in the summer of 2012. The results suggest that satellite-based monitoring of atmospheric preconditioning could be a critical source of information in predicting extreme sea ice melting events in the Arctic.

scholarly journals Inorganic carbon dynamics of melt-pond-covered first-year sea ice in the Canadian Arctic

2015 ◽  
Vol 12 (6) ◽  
pp. 2047-2061 ◽  
Author(s):  
N.-X. Geilfus ◽  
R. J. Galley ◽  
O. Crabeck ◽  
T. Papakyriakou ◽  
J. Landy ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
First Year ◽  
Co2 Fluxes ◽  
Ice Melt ◽  
Melt Pond ◽  
Melt Ponds ◽  
Arctic Sea

Abstract. Melt pond formation is a common feature of spring and summer Arctic sea ice, but the role and impact of sea ice melt and pond formation on both the direction and size of CO2 fluxes between air and sea is still unknown. Here we report on the CO2–carbonate chemistry of melting sea ice, melt ponds and the underlying seawater as well as CO2 fluxes at the surface of first-year landfast sea ice in the Resolute Passage, Nunavut, in June 2012. Early in the melt season, the increase in ice temperature and the subsequent decrease in bulk ice salinity promote a strong decrease of the total alkalinity (TA), total dissolved inorganic carbon (TCO2) and partial pressure of CO2 (pCO2) within the bulk sea ice and the brine. As sea ice melt progresses, melt ponds form, mainly from melted snow, leading to a low in situ melt pond pCO2 (36 μatm). The percolation of this low salinity and low pCO2 meltwater into the sea ice matrix decreased the brine salinity, TA and TCO2, and lowered the in situ brine pCO2 (to 20 μatm). This initial low in situ pCO2 observed in brine and melt ponds results in air–ice CO2 fluxes ranging between −0.04 and −5.4 mmol m−2 day−1 (negative sign for fluxes from the atmosphere into the ocean). As melt ponds strive to reach pCO2 equilibrium with the atmosphere, their in situ pCO2 increases (up to 380 μatm) with time and the percolation of this relatively high concentration pCO2 meltwater increases the in situ brine pCO2 within the sea ice matrix as the melt season progresses. As the melt pond pCO2 increases, the uptake of atmospheric CO2 becomes less significant. However, since melt ponds are continuously supplied by meltwater, their in situ pCO2 remains undersaturated with respect to the atmosphere, promoting a continuous but moderate uptake of CO2 (~ −1 mmol m−2 day−1) into the ocean. Considering the Arctic seasonal sea ice extent during the melt period (90 days), we estimate an uptake of atmospheric CO2 of −10.4 Tg of C yr−1. This represents an additional uptake of CO2 associated with Arctic sea ice that needs to be further explored and considered in the estimation of the Arctic Ocean's overall CO2 budget.

Freshwater under the MOSAiC floe: implications of under-ice melt ponds for mass balance

2021 ◽  
Author(s):  
Madison Smith ◽  
Luisa von Albedyll ◽  
Ian Raphael ◽  
Ilkka Matero ◽  
Benjamin A. Lange
Keyword(s):  
Sea Ice ◽  
Mass Balance ◽  
Early Summer ◽  
The Arctic ◽  
Ice Melt ◽  
Freshwater Ponds ◽  
Ice Floes ◽  
Freshwater Inputs ◽  
June July ◽  
The Impact

&lt;p&gt;During the melt season in the Arctic, freshwater ponds can accumulate under ice floes as a result of local snow and sea ice melt, far from terrestrial freshwater inputs. Under-ice freshwater ponds have been suggested to play a role in the summer sea ice mass balance both by isolating the sea ice from salty, warmer water below, and by driving formation of ice &amp;#8216;false bottoms&amp;#8217; at the interface of the under-ice pond and the underlying ocean.&amp;#160;&lt;/p&gt;&lt;p&gt;The MOSAiC drift expedition in the Central Arctic observed the presence of under-ice ponds and false bottoms beginning early in the melt season (June - July) at primarily first-year ice locations on the floe. We examine the prevalence and drivers of these ponds and resulting false bottoms during this period. Additionally, we explore the impact for mass balance using observations from ablation stakes and a 1D model, where freshwater ponds can not only delay summer melt but also result in growth. We speculate that the unique history of the MOSAiC floe likely led to a relatively high occurrence of these features, but the results also suggest that freshwater under-ice ponds and false bottoms may be more common and more persistent in early summer in the Arctic than previously thought. Both have implications for the broader ice-ocean system, for example by reducing fluxes between the ice and the ocean, isolating the primary producers in ice from pelagic nutrient sources, and altering the optical properties.&lt;/p&gt;

Eddy covariance flux measurements of momentum, heat and carbon dioxide in Hudson Bay at the onset of sea ice melt 

2021 ◽  
Author(s):  
Richard Sims ◽  
Brian Butterworth ◽  
Tim Papakyriakou ◽  
Mohamed Ahmed ◽  
Brent Else
Keyword(s):  
Carbon Dioxide ◽  
Gas Exchange ◽  
Sea Ice ◽  
Eddy Covariance ◽  
Open Water ◽  
The Arctic ◽  
Gas Transfer ◽  
Hudson Bay ◽  
Flux Measurements ◽  
Ice Fraction

&lt;p&gt;Remoteness and tough conditions have made the Arctic Ocean historically difficult to access; until recently this has resulted in an undersampling of trace gas and gas exchange measurements. The seasonal cycle of sea ice completely transforms the air sea interface and the dynamics of gas exchange. To make estimates of gas exchange in the presence of sea ice, sea ice fraction is frequently used to scale open water gas transfer parametrisations. It remains unclear whether this scaling is appropriate for all sea ice regions. Ship based eddy covariance measurements were made in Hudson Bay during the summer of 2018 from the icebreaker CCGS Amundsen. We will present fluxes of carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;), heat and momentum and will show how they change around the Hudson Bay polynya under varying sea ice conditions. We will explore how these fluxes change with wind speed and sea ice fraction. As freshwater stratification was encountered during the cruise, we will compare our measurements with other recent eddy covariance flux measurements made from icebreakers and also will compare our turbulent CO&lt;sub&gt;2&amp;#160;&lt;/sub&gt;fluxes with bulk fluxes calculated using underway and surface bottle pCO&lt;sub&gt;2&lt;/sub&gt;&amp;#160;data.&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals Extreme Warming in the Kara Sea and Barents Sea during the Winter Period 2000–16

2017 ◽  
Vol 30 (22) ◽  
pp. 8913-8927 ◽  
Author(s):  
Svenja H. E. Kohnemann ◽  
Günther Heinemann ◽  
David H. Bromwich ◽  
Oliver Gutjahr
Keyword(s):  
Sea Ice ◽  
Air Temperature ◽  
Barents Sea ◽  
Kara Sea ◽  
The Arctic ◽  
Winter Period ◽  
Limited Area ◽  
Spatial And Temporal Variability ◽  
Large Variability ◽  
Air Temperatures

The regional climate model COSMO in Climate Limited-Area Mode (COSMO-CLM or CCLM) is used with a high resolution of 15 km for the entire Arctic for all winters 2002/03–2014/15. The simulations show a high spatial and temporal variability of the recent 2-m air temperature increase in the Arctic. The maximum warming occurs north of Novaya Zemlya in the Kara Sea and Barents Sea between March 2003 and 2012 and is responsible for up to a 20°C increase. Land-based observations confirm the increase but do not cover the maximum regions that are located over the ocean and sea ice. Also, the 30-km version of the Arctic System Reanalysis (ASR) is used to verify the CCLM for the overlapping time period 2002/03–2011/12. The differences between CCLM and ASR 2-m air temperatures vary slightly within 1°C for the ocean and sea ice area. Thus, ASR captures the extreme warming as well. The monthly 2-m air temperatures of observations and ERA-Interim data show a large variability for the winters 1979–2016. Nevertheless, the air temperature rise since the beginning of the twenty-first century is up to 8 times higher than in the decades before. The sea ice decrease is identified as the likely reason for the warming. The vertical temperature profiles show that the warming has a maximum near the surface, but a 0.5°C yr−1 increase is found up to 2 km. CCLM, ASR, and also the coarser resolved ERA-Interim data show that February and March are the months with the highest 2-m air temperature increases, averaged over the ocean and sea ice area north of 70°N; for CCLM the warming amounts to an average of almost 5°C for 2002/03–2011/12.

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