Using ship-borne observations of methane isotopic ratio in the Arctic Ocean to understand methane sources in the Arctic

Abstract. Due to the large variety and heterogeneity of sources in remote areas hard to document, the Arctic regional methane budget remain very uncertain. In situ campaigns provide valuable data sets to reduce these uncertainties. Here we analyse data from the SWERUS-C3 campaign, on-board the icebreaker Oden, that took place during summer 2014 in the Arctic Ocean along the Northern Siberian and Alaskan shores. Total concentrations of methane, as well as isotopic ratios were measured continuously during this campaign for 35 days in July and August 2014. Using a chemistry-transport model, we link observed concentrations and isotopic ratios to regional emissions and hemispheric transport structures. A simple inversion system helped constraining source signatures from wetlands in Siberia and Alaska and oceanic sources, as well as the isotopic composition of lower stratosphere air masses. The variation in the signature of low stratosphere air masses, due to strongly fractionating chemical reactions in the stratosphere, was suggested to explain a large share of the observed variability in isotopic ratios. These points at required efforts to better simulate large scale transport and chemistry patterns to use isotopic data in remote areas. It is found that constant and homogeneous source signatures for each type of emission in the region (mostly wetlands and oil and gas industry) is not compatible with the strong synoptic isotopic signal observed in the Arctic. A regional gradient in source signatures is highlighted between Siberian and Alaskan wetlands, the later ones having a lighter signatures than the first ones. Arctic continental shelf sources are suggested to be a mixture of methane from a dominant thermogenic origin and a secondary biogenic one, consistent with previous in-situ isotopic analysis of seepage along the Siberian shores.

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Using ship-borne observations of methane isotopic ratio in the Arctic Ocean to understand methane sources in the Arctic

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-3987-2020 ◽

2020 ◽

Vol 20 (6) ◽

pp. 3987-3998 ◽

Cited By ~ 3

Author(s):

Antoine Berchet ◽

Isabelle Pison ◽

Patrick M. Crill ◽

Brett Thornton ◽

Philippe Bousquet ◽

...

Keyword(s):

Arctic Ocean ◽

Large Scale ◽

Oil And Gas ◽

Lower Stratosphere ◽

Transport Model ◽

Isotopic Ratio ◽

Oil And Gas Industry ◽

The Arctic ◽

Isotopic Ratios ◽

Air Masses

Abstract. Characterizing methane sources in the Arctic remains challenging due to the remoteness, heterogeneity and variety of such emissions. In situ campaigns provide valuable datasets to reduce these uncertainties. Here we analyse data from the summer 2014 SWERUS-C3 campaign in the eastern Arctic Ocean, off the shore of Siberia and Alaska. Total concentrations of methane, as well as relative concentrations of 12CH4 and 13CH4, were measured continuously during this campaign for 35 d in July and August. Using a chemistry-transport model, we link observed concentrations and isotopic ratios to regional emissions and hemispheric transport structures. A simple inversion system helped constrain source signatures from wetlands in Siberia and Alaska, and oceanic sources, as well as the isotopic composition of lower-stratosphere air masses. The variation in the signature of lower-stratosphere air masses, due to strongly fractionating chemical reactions in the stratosphere, was suggested to explain a large share of the observed variability in isotopic ratios. These results point towards necessary efforts to better simulate large-scale transport and chemistry patterns to make relevant use of isotopic data in remote areas. It is also found that constant and homogeneous source signatures for each type of emission in a given region (mostly wetlands and oil and gas industry in our case at high latitudes) are not compatible with the strong synoptic isotopic signal observed in the Arctic. A regional gradient in source signatures is highlighted between Siberian and Alaskan wetlands, the latter having lighter signatures (more depleted in 13C). Finally, our results suggest that marine emissions of methane from Arctic continental-shelf sources are dominated by thermogenic-origin methane, with a secondary biogenic source as well.

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A satellite-based estimate of combustion aerosol cloud microphysical effects over the Arctic Ocean

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-14949-2018 ◽

2018 ◽

Vol 18 (20) ◽

pp. 14949-14964 ◽

Cited By ~ 6

Author(s):

Lauren M. Zamora ◽

Ralph A. Kahn ◽

Klaus B. Huebert ◽

Andreas Stohl ◽

Sabine Eckhardt

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Large Scale ◽

Transport Model ◽

The Arctic ◽

Energy Budgets ◽

Precipitation Frequency ◽

Aerosol Cloud ◽

The Arctic Ocean ◽

Combustion Aerosols

Abstract. Climate predictions for the rapidly changing Arctic are highly uncertain, largely due to a poor understanding of the processes driving cloud properties. In particular, cloud fraction (CF) and cloud phase (CP) have major impacts on energy budgets, but are poorly represented in most models, often because of uncertainties in aerosol–cloud interactions. Here, we use over 10 million satellite observations coupled with aerosol transport model simulations to quantify large-scale microphysical effects of aerosols on CF and CP over the Arctic Ocean during polar night, when direct and semi-direct aerosol effects are minimal. Combustion aerosols over sea ice are associated with very large (∼10 W m−2) differences in longwave cloud radiative effects at the sea ice surface. However, co-varying meteorological changes on factors such as CF likely explain the majority of this signal. For example, combustion aerosols explain at most 40 % of the CF differences between the full dataset and the clean-condition subset, compared to between 57 % and 91 % of the differences that can be predicted by co-varying meteorology. After normalizing for meteorological regime, aerosol microphysical effects have small but significant impacts on CF, CP, and precipitation frequency on an Arctic-wide scale. These effects indicate that dominant aerosol–cloud microphysical mechanisms are related to the relative fraction of liquid-containing clouds, with implications for a warming Arctic.

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Effects of Climatic Drivers and Teleconnections on Late 20th Century Trends in Spring Freshet of Four Major Arctic-Draining Rivers

Water ◽

10.3390/w13020179 ◽

2021 ◽

Vol 13 (2) ◽

pp. 179

Author(s):

Roxanne Ahmed ◽

Terry Prowse ◽

Yonas Dibike ◽

Barrie Bonsal

Keyword(s):

Arctic Ocean ◽

Large Scale ◽

Southern Oscillation ◽

Rate Of Change ◽

The Arctic ◽

Late 20Th Century ◽

Basin Scale ◽

The Arctic Ocean ◽

Spring Freshet ◽

Climatic Drivers

Spring freshet is the dominant annual discharge event in all major Arctic draining rivers with large contributions to freshwater inflow to the Arctic Ocean. Research has shown that the total freshwater influx to the Arctic Ocean has been increasing, while at the same time, the rate of change in the Arctic climate is significantly higher than in other parts of the globe. This study assesses the large-scale atmospheric and surface climatic conditions affecting the magnitude, timing and regional variability of the spring freshets by analyzing historic daily discharges from sub-basins within the four largest Arctic-draining watersheds (Mackenzie, Ob, Lena and Yenisei). Results reveal that climatic variations closely match the observed regional trends of increasing cold-season flows and earlier freshets. Flow regulation appears to suppress the effects of climatic drivers on freshet volume but does not have a significant impact on peak freshet magnitude or timing measures. Spring freshet characteristics are also influenced by El Niño-Southern Oscillation, the Pacific Decadal Oscillation, the Arctic Oscillation and the North Atlantic Oscillation, particularly in their positive phases. The majority of significant relationships are found in unregulated stations. This study provides a key insight into the climatic drivers of observed trends in freshet characteristics, whilst clarifying the effects of regulation versus climate at the sub-basin scale.

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Oil Spills in the Arctic Ocean: Extent of Spreading and Possibility of Large-Scale Thermal Effects

Science ◽

10.1126/science.186.4166.843-b ◽

1974 ◽

Vol 186 (4166) ◽

pp. 843-845

Author(s):

R. C. Ayers ◽

H. O. Jahns ◽

J. L. Glaeser

Keyword(s):

Arctic Ocean ◽

Thermal Effects ◽

Large Scale ◽

Oil Spills ◽

The Arctic ◽

The Arctic Ocean

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Cryospheric Impacts of Soviet River Diversion Schemes

Annals of Glaciology ◽

10.3189/1984aog5-1-61-68 ◽

1984 ◽

Vol 5 ◽

pp. 61-68 ◽

Cited By ~ 4

Author(s):

T. Holt ◽

P. M. Kelly ◽

B. S. G. Cherry

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

River Discharge ◽

Large Scale ◽

Arctic Sea Ice ◽

The Arctic ◽

Sea Ice Concentration ◽

Ice Concentration ◽

The Arctic Ocean ◽

The Impact

Soviet plans to divert water from rivers flowing into the Arctic Ocean have led to research into the impact of a reduction in discharge on Arctic sea ice. We consider the mechanisms by which discharge reductions might affect sea-ice cover and then test various hypotheses related to these mechanisms. We find several large areas over which sea-ice concentration correlates significantly with variations in river discharge, supporting two particular hypotheses. The first hypothesis concerns the area where the initial impacts are likely to which is the Kara Sea. Reduced riverflow is associated occur, with decreased sea-ice concentration in October, at the time of ice formation. This is believed to be the result of decreased freshening of the surface layer. The second hypothesis concerns possible effects on the large-scale current system of the Arctic Ocean and, in particular, on the inflow of Atlantic and Pacific water. These effects occur as a result of changes in the strength of northward-flowing gradient currents associated with variations in river discharge. Although it is still not certain that substantial transfers of riverflow will take place, it is concluded that the possibility of significant cryospheric effects and, hence, large-scale climate impact should not be neglected.

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Assessment of Temperature and Specific Humidity Inversions and Their Relationships in Three Global Reanalysis Products over the Arctic Ocean

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-20-0079.1 ◽

2021 ◽

Vol 60 (4) ◽

pp. 493-511

Author(s):

Liang Chang ◽

Shiqiang Wen ◽

Guoping Gao ◽

Zhen Han ◽

Guiping Feng ◽

...

Keyword(s):

Arctic Ocean ◽

Specific Humidity ◽

The Arctic ◽

Weather Forecasts ◽

The Arctic Ocean ◽

Temperature Inversions ◽

Global Reanalysis ◽

Less Common Multiple ◽

Better Than

AbstractCharacteristics of temperature inversions (TIs) and specific humidity inversions (SHIs) and their relationships in three of the latest global reanalyses—the European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-I), the Japanese 55-year Reanalysis (JRA-55), and the ERA5—are assessed against in situ radiosonde (RS) measurements from two expeditions over the Arctic Ocean. All reanalyses tend to detect many fewer TI and SHI occurrences, together with much less common multiple TIs and SHIs per profile than are seen in the RS data in summer 2008, winter 2015, and spring 2015. The reanalyses generally depict well the relationships among TI characteristics seen in RS data, except for the TIs below 400 m in summer, as well as above 1000 m in summer and winter. The depth is simulated worst by the reanalyses among the SHI characteristics, which may result from its sensitivity to the uncertainties in specific humidity in the reanalyses. The strongest TI per profile in RS data exhibits more robust dependency on surface conditions than the strongest SHI per profile, and the former is better presented by the reanalyses than the latter. Furthermore, all reanalyses have difficulties simulating the relationships between TIs and SHIs, together with the correlations between the simultaneous inversions. The accuracy and vertical resolution in the reanalyses are both important to properly capture occurrence and characteristics of the Arctic inversions. In general, ERA5 performs better than ERA-I and JRA-55 in depicting the relationships among the TIs. However, the representation of SHIs is more challenging than TIs in all reanalyses over the Arctic Ocean.

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Arctic sea-ice area and volume production:1996/97 versus 1997/98

Annals of Glaciology ◽

10.3189/172756402781817527 ◽

2002 ◽

Vol 34 ◽

pp. 447-453 ◽

Cited By ~ 10

Author(s):

Ron Kwok

Keyword(s):

Arctic Ocean ◽

Large Scale ◽

Heat Budget ◽

Ice Cover ◽

Arctic Sea Ice ◽

The Arctic ◽

Ice Thickness ◽

The Arctic Ocean ◽

Volume Production ◽

Area And Volume

AbstractThe RADARSAT geophysical processor system (RGPS) produces measurements of ice motion and estimates of ice thickness using repeat synthetic aperture radar maps of the Arctic Ocean. From the RGPS products, we compute the net deformation and advection of the winter ice cover using the motion observations, and the seasonal ice area and volume production using the estimates of ice thickness. The results from the winters of 1996/97 and 1997/98 are compared. The second winter is of particular interest because it coincides with the Surface Heat Budget of the Arctic Ocean (SHEBA) field program. The character of the deformation of the ice cover from the two years is very different. Over a domain covering a large part of the western Arctic Ocean (~2.5 × 106 km2), the net divergence of that area during the 6 months of the first winter was 2.7% and for the second winter was 49.3%. In a subregion where the SHEBA camp was located, the net divergence was almost 38% compared to a net divergence of the same subregion of ~9% in 1996/97. The resulting deformation created a much larger volume of seasonal ice than in the earlier year. The net seasonal ice-volume production is 1.6 times (0.38 m vs 0.62 m) that of the first year. In addition to the larger divergence, this part of the ice cover advected a longer distance toward the Chukchi Sea over the same time-span. The total coverage of multi-year ice remained almost identical at ~2.08 × 106 km2, or 83% of the initial area of the domain. In this paper, we compare the behavior of the ice cover over the two winters and discuss these observations in the context of large-scale ice motion and atmospheric-pressure pattern.

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INTAROS synthesis of gap analysis of the existing Arctic observing systems

10.5194/egusphere-egu2020-20091 ◽

2020 ◽

Author(s):

Roberta Pirazzini ◽

Michael Tjernström ◽

Stein Sandven ◽

Hanne Sagen ◽

Torill Hamre ◽

...

Keyword(s):

Arctic Ocean ◽

Gap Analysis ◽

Satellite Observations ◽

The Arctic ◽

Reference Level ◽

Data Handling ◽

Network Concept ◽

The Arctic Ocean ◽

Observing Systems

A comprehensive assessment of a substantial subset of Arctic observing systems, data collections and satellite products across scientific disciplines was carried out in INTAROS, also including data repositories and a brief scientific gap analysis. The assessments cover a multitude of aspects such as sustainability, technical maturity and data handling for the entire chain from observation to users, including metadata procedures and availability to data. Community based environment monitoring programs were surveyed and assessed separately; they do not form part of the present assessment.The assessed observing systems were first ranked according to general sustainability and other aspects, were analyzed subsequently. While the range of sustainability is large, it was found that high scores on all other aspects, such as for data handling and technical maturity, are more likely for systems with high sustainability. Moreover, many systems with high sustainability, as well as advanced systems for data handling and availability in place, resulted from national commitments to international monitoring or infrastructure programs, several of which are not necessarily particular to the Arctic.Traditionally, terrestrial and atmospheric observation network assessments build on the network concept with a &#8220;comprehensive&#8221; level including all observations, a &#8220;baseline&#8221; level of an agreed subset of sustained observations, and a &#8220;reference&#8221; level, with observations adhering to specific calibrations and traceability criteria. Examples from atmospheric observations are the &#8220;comprehensive&#8221; global GCOS radiosounding network, the &#8220;baseline&#8221; GUAN (GCOS Upper Air Network) and &#8220;reference&#8221; GRUAN (GCOS Reference Upper Air Network) networks. With the lack of in-situ observations especially from the Arctic Ocean and the logistical difficulties to deploy new stations, it was concluded that this concept does not work well in the Arctic.In summary, we recommend that:<ul><li>advancement in Arctic observing should be done in international global or regional programs with well-established routines and procedures, rather than to invest in new Arctic-specific programs</li> <li>investments in new instruments and techniques be done at already established sites, to benefit interdisciplinary studies and optimize infrastructure costs</li> <li>more observations be based on ships of opportunity and that a subset of ocean, sea-ice and atmosphere observations always be made on all research expeditions, regardless of their scientific aim</li> <li>the funding structures for science expeditions is reviewed to maintain, and preferably increase, the number of expeditions and to safeguard funding for appropriate data handling and storage</li> <li>observing-network concept for the atmosphere over the Arctic Ocean is revised, so that coupled reanalyses represent the &#8220;comprehensive level&#8221;, satellite observations complemented with available in-situ data is the &#8220;baseline level&#8221;, while scientific expeditions is the &#8220;reference level&#8221;. This requires substantial improvements in reanalysis, better numerical models and data assimilation, better satellite observations and improved data handling and accessibility for scientific expeditions.</li> </ul>

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