scholarly journals The encoding of wind forcing into the Pacific-Arctic pressure head, Chukchi Sea ice retreat and late-summer Barrow Canyon water masses

2019 ◽  
Vol 162 ◽  
pp. 22-31 ◽  
Author(s):  
Stephen Okkonen ◽  
Carin Ashjian ◽  
Robert G. Campbell ◽  
Philip Alatalo
Keyword(s):  
Sea Ice ◽  
Chukchi Sea ◽  
Late Summer ◽  
Pressure Head ◽  
Water Masses ◽  
Wind Forcing ◽  
The Pacific ◽  
Ice Retreat ◽  
Sea Ice Retreat

scholarly journals Variability in spring phytoplankton blooms associated with ice retreat timing in the Pacific Arctic from 2003–2019

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0261418
Author(s):  
Hisatomo Waga ◽  
Hajo Eicken ◽  
Toru Hirawake ◽  
Yasushi Fukamachi
Keyword(s):  
Sea Ice ◽  
Phytoplankton Biomass ◽  
Phytoplankton Bloom ◽  
Chukchi Sea ◽  
Gaussian Function ◽  
Phytoplankton Blooms ◽  
The Pacific ◽  
Marginal Ice Zone ◽  
Ice Retreat ◽  
Sea Ice Retreat

The Arctic is experiencing rapid changes in sea-ice seasonality and extent, with significant consequences for primary production. With the importance of accurate monitoring of spring phytoplankton dynamics in a changing Arctic, this study further examines the previously established critical relationship between spring phytoplankton bloom types and timing of the sea-ice retreat for broader temporal and spatial coverages, with a particular focus on the Pacific Arctic for 2003–2019. To this end, time-series of satellite-retrieved phytoplankton biomass were modeled using a parametric Gaussian function, as an effective approach to capture the development and decay of phytoplankton blooms. Our sensitivity analysis demonstrated accurate estimates of timing and presence/absence of peaks in phytoplankton biomass even with some missing values, suggesting the parametric Gaussian function is a powerful tool for capturing the development and decay of phytoplankton blooms. Based on the timing and presence/absence of a peak in phytoplankton biomass and following the classification developed by the previous exploratory work, spring bloom types are classified into three groups (under-ice blooms, probable under-ice blooms, and marginal ice zone blooms). Our results showed that the proportion of under-ice blooms was higher in the Chukchi Sea than in the Bering Sea. The probable under-ice blooms registered as the dominant bloom types in a wide area of the Pacific Arctic, whereas the marginal ice zone bloom was a relatively minor bloom type across the Pacific Arctic. Associated with a shift of sea-ice retreat timing toward earlier dates, we confirmed previous findings from the Chukchi Sea of recent shifts in phytoplankton bloom types from under-ice blooms to marginal ice zone blooms and demonstrated that this pattern holds for the broader Pacific Arctic sector for the time period 2003–2019. Overall, the present study provided additional evidence of the changing sea-ice retreat timing that can drive variations in phytoplankton bloom dynamics, which contributes to addressing the detection and consistent monitoring of the biophysical responses to the changing environments in the Pacific Arctic.

scholarly journals Phytoplankton distribution in unusually low sea ice cover over the Pacific Arctic

2012 ◽  
Vol 9 (11) ◽  
pp. 4835-4850 ◽  
Author(s):  
P. Coupel ◽  
H. Y. Jin ◽  
M. Joo ◽  
R. Horner ◽  
H. A. Bouvet ◽  
...  
Keyword(s):  
Sea Ice ◽  
Marine Ecosystem ◽  
Environmental Parameters ◽  
Arctic Basin ◽  
Ice Cover ◽  
Phytoplankton Distribution ◽  
The Pacific ◽  
Ice Retreat ◽  
Sea Ice Retreat ◽  
The Impact

Abstract. A large part of the Pacific Arctic basin experiences ice-free conditions in summer as a result of sea ice cover steadily decreasing over the last decades. To evaluate the impact of sea ice retreat on the marine ecosystem, phytoplankton in situ observations were acquired over the Chukchi shelf and the Canadian basin in 2008, a year of high melting. Pigment analyses and taxonomy enumerations were used to characterise the distribution of main phytoplanktonic groups. Marked spatial variability of the phytoplankton distribution was observed in summer 2008. Comparison of eight phytoplankton functional groups and 3 size-classes (pico-, nano- and micro-phytoplankton) also showed significant differences in abundance, biomass and distribution between summer of low ice cover (2008) and heavy ice summer (1994). Environmental parameters such as freshening, stratification, light and nutrient availability are discussed as possible causes to explain the observed differences in phytoplankton community structure between 1994 and 2008.

scholarly journals Summer Changes in Water Mass Characteristics and Vertical Thermohaline Structure in the Eastern Chukchi Sea, 1974–2017

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1434 ◽  
Author(s):  
Yayu Yang ◽  
Xuezhi Bai
Keyword(s):  
Water Mass ◽  
Chukchi Sea ◽  
World Ocean ◽  
Water Masses ◽  
Thermohaline Structure ◽  
The Pacific ◽  
Previous Definition ◽  
Southern Central ◽  
Ice Retreat ◽  
Definition Of

Hydrographic data from the World Ocean Database 2013 and the Chinese National Arctic Research Expedition were used to investigate the summertime changes in the eastern Chukchi Sea from 1974 to 2017. Owing to the Pacific inflow and timing of the sea ice retreat, water masses and vertical thermohaline structures in the eastern Chukchi Sea have changed but with regional differences. The entire eastern Chukchi Sea warmed up with significant temperature increase in the central shelf; however, the surface and bottom salinity in the southern, central, and northern shelves exhibited different trends. The northward extension of the Pacific Summer Water after 1997 influenced the summer hydrography significantly. Moreover, the data reveal changes in the characteristics of various water masses. Both Bering Summer Water (BSW) and Pacific Winter Water in the deeper layer became saltier, whereas the Alaskan Coastal Water in the upper layer became fresher after 1997. The previous definition of the BSW should be modified to include the warming water mass in the southern Chukchi Sea in the more recent years. Furthermore, the vertical thermohaline structure over the Chukchi shelves experienced considerable changes in its characteristics due to the combined effects of the Pacific inflow and surface forcing.

scholarly journals Contributions of advection and melting processes to the decline in sea ice in the Pacific sector of the Arctic Ocean

2019 ◽  
Author(s):  
Haibo Bi ◽  
Qinghua Yang ◽  
Xi Liang ◽  
Haijun Huang
Keyword(s):  
Sea Ice ◽  
Melting Process ◽  
The Arctic ◽  
Positive Trend ◽  
Ice Coverage ◽  
The Pacific ◽  
Ice Retreat ◽  
The Mean ◽  
Sea Ice Retreat ◽  
Increasing Trends

Abstract. The Pacific–Arctic (PA) Ocean is a region sensitive to climate change. Given the alarming changes in sea ice cover during recent years, knowledge of sea ice loss with respect to ice advection and melting processes has become critical. With satellite-derived products from the National Snow and Ice Center (NSIDC), a 38-yr record (1979–2016) of the loss in sea ice area in summer within the Pacific-Arctic (PA) sector due to the two processes is obtained. The average sea ice outflow from the PA to the Atlantic-Arctic (AA) Ocean during the summer season (June–September) reaches 173 × 103 km2, which corresponds to approximately 34 % of the mean annual export (October to September). Over the investigated period, a positive trend of 4.2 × 103 km2/yr is also observed for the outflow field in summer. The mean estimate of sea ice retreat within the PA associated with summer melting is 1.66 × 106 km2, with a positive trend of 53.1 × 103 km2/yr. As a result, the increasing trends of ice retreat caused by outflow and melting together contribute to a stronger decrease in sea ice coverage within the PA (57.3 × 103 km2/yr) in summer. In percentage terms, the melting process accounts for 90.4 % of the sea ice retreat in the PA in summer, whereas the remaining 9.6 % is explained by the outflow process, on average. Moreover, our analysis suggests that the connections are relatively strong (R = 0.63), moderate (R = −0.46), and weak (R = −0.24) between retreat of sea ice and the winds associated with the Dipole Anomaly (DA), North Atlantic Oscillation (NAO), and Arctic Oscillation (AO), respectively. The DA participates by impacting both the advection (R = 0.74) and melting (R = 0.55) processes, whereas the NAO affects the melting process (R = −0.46).

scholarly journals Variability, trends, and predictability of seasonal sea ice retreat and advance in the Chukchi Sea

2016 ◽  
Vol 121 (10) ◽  
pp. 7308-7325 ◽  
Author(s):  
Mark C. Serreze ◽  
Alex D. Crawford ◽  
Julienne C. Stroeve ◽  
Andrew P. Barrett ◽  
Rebecca A. Woodgate
Keyword(s):  
Sea Ice ◽  
Chukchi Sea ◽  
Ice Retreat ◽  
Sea Ice Retreat

scholarly journals Contributions of advection and melting processes to the decline in sea ice in the Pacific sector of the Arctic Ocean

2019 ◽  
Vol 13 (5) ◽  
pp. 1423-1439 ◽  
Author(s):  
Haibo Bi ◽  
Qinghua Yang ◽  
Xi Liang ◽  
Liang Zhang ◽  
Yunhe Wang ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Melting Process ◽  
The Arctic ◽  
Positive Trend ◽  
The Pacific ◽  
The Arctic Ocean ◽  
Ice Retreat ◽  
The Mean ◽  
Sea Ice Retreat

Abstract. The Pacific sector of the Arctic Ocean (PA, hereafter) is a region sensitive to climate change. Given the alarming changes in sea ice cover during recent years, knowledge of sea ice loss with respect to ice advection and melting processes has become critical. With satellite-derived products from the National Snow and Ice Center (NSIDC), a 38-year record (1979–2016) of the loss in sea ice area in summer within the Pacific-Arctic (PA) sector due to the two processes is obtained. The average sea ice outflow from the PA to the Atlantic-Arctic (AA) Ocean during the summer season (June–September) reaches 0.173×106 km2, which corresponds to approximately 34 % of the mean annual export (October to September). Over the investigated period, a positive trend of 0.004×106 km2 yr−1 is also observed for the outflow field in summer. The mean estimate of sea ice retreat within the PA associated with summer melting is 1.66×106 km2, with a positive trend of 0.053×106 km2 yr−1. As a result, the increasing trends of ice retreat caused by outflow and melting together contribute to a stronger decrease in sea ice coverage within the PA (0.057×106 km2 yr−1) in summer. In percentage terms, the melting process accounts for 90.4 % of the sea ice retreat in the PA in summer, whereas the remaining 9.6 % is explained by the outflow process, on average. Moreover, our analysis suggests that the connections are relatively strong (R=0.63), moderate (R=-0.46), and weak (R=-0.24) between retreat of sea ice and the winds associated with the dipole anomaly (DA), North Atlantic Oscillation (NAO), and Arctic Oscillation (AO), respectively. The DA participates by impacting both the advection (R=0.74) and melting (R=0.55) processes, whereas the NAO affects the melting process (R=-0.46).

scholarly journals Patterns of Sea Ice Retreat in the Transition to a Seasonally Ice-Free Arctic

2016 ◽  
Vol 29 (19) ◽  
pp. 6993-7008 ◽  
Author(s):  
Patricia DeRepentigny ◽  
L. Bruno Tremblay ◽  
Robert Newton ◽  
Stephanie Pfirman
Keyword(s):  
Sea Ice ◽  
Sea Level ◽  
Large Scale ◽  
System Model ◽  
The Arctic ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The Pacific ◽  
Ice Retreat ◽  
Sea Ice Retreat

Abstract The patterns of sea ice retreat in the Arctic Ocean are investigated using two global climate models (GCMs) that have profound differences in their large-scale mean winter atmospheric circulation and sea ice drift patterns. The Community Earth System Model Large Ensemble (CESM-LE) presents a mean sea level pressure pattern that is in general agreement with observations for the late twentieth century. The Community Climate System Model, version 4 (CCSM4), exhibits a low bias in its mean sea level pressure over the Arctic region with a deeper Icelandic low. A dynamical mechanism is presented in which large-scale mean winter atmospheric circulation has significant effect on the following September sea ice extent anomaly by influencing ice divergence in specific areas. A Lagrangian model is used to backtrack the 80°N line from the approximate time of the melt onset to its prior positions throughout the previous winter and quantify the divergence across the Pacific and Eurasian sectors of the Arctic. It is found that CCSM4 simulates more sea ice divergence in the Beaufort and Chukchi Seas and less divergence in the Eurasian seas when compared to CESM-LE, leading to a Pacific-centric sea ice retreat. On the other hand, CESM-LE shows a more symmetrical retreat between the Pacific, Eurasian, and Atlantic sectors of the Arctic. Given that a positive trend in the Arctic Oscillation (AO) index, associated with low sea level pressure anomalies in the Arctic, is a robust feature of GCMs participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5), these results suggest that the sea ice retreat in the Pacific sector could be amplified during the transition to a seasonal ice cover.

scholarly journals Distribution of Arctic and Pacific copepods and their habitat in the northern Bering and Chukchi seas

2016 ◽  
Vol 13 (15) ◽  
pp. 4555-4567 ◽  
Author(s):  
Hiroko Sasaki ◽  
Kohei Matsuno ◽  
Amane Fujiwara ◽  
Misaki Onuka ◽  
Atsushi Yamaguchi ◽  
...  
Keyword(s):  
Sea Ice ◽  
Cold Water ◽  
Generalized Additive Models ◽  
Open Water ◽  
Bottom Layer ◽  
Additive Models ◽  
Water Masses ◽  
Positive Effects ◽  
Ice Retreat ◽  
Sea Ice Retreat

Abstract. The advection of warm Pacific water and the reduction in sea ice in the western Arctic Ocean may influence the abundance and distribution of copepods, a key component of food webs. To quantify the factors affecting the abundance of copepods in the northern Bering and Chukchi seas, we constructed habitat models explaining the spatial patterns of large and small Arctic and Pacific copepods separately. Copepods were sampled using NORPAC (North Pacific Standard) nets. The structures of water masses indexed by principle component analysis scores, satellite-derived timing of sea ice retreat, bottom depth and chlorophyll a concentration were integrated into generalized additive models as explanatory variables. The adequate models for all copepods exhibited clear continuous relationships between the abundance of copepods and the indexed water masses. Large Arctic copepods were abundant at stations where the bottom layer was saline; however they were scarce at stations where warm fresh water formed the upper layer. Small Arctic copepods were abundant at stations where the upper layer was warm and saline and the bottom layer was cold and highly saline. In contrast, Pacific copepods were abundant at stations where the Pacific-origin water mass was predominant (i.e. a warm, saline upper layer and saline and a highly saline bottom layer). All copepod groups showed a positive relationship with early sea ice retreat. Early sea ice retreat has been reported to initiate spring blooms in open water, allowing copepods to utilize more food while maintaining their high activity in warm water without sea ice and cold water. This finding indicates that early sea ice retreat has positive effects on the abundance of all copepod groups in the northern Bering and Chukchi seas, suggesting a change from a pelagic–benthic-type ecosystem to a pelagic–pelagic type.

scholarly journals Pacific Water Transport in the Western Arctic Ocean Simulated by an Eddy-Resolving Coupled Sea Ice–Ocean Model

2009 ◽  
Vol 39 (9) ◽  
pp. 2194-2211 ◽  
Author(s):  
Eiji Watanabe ◽  
Hiroyasu Hasumi
Keyword(s):  
Sea Ice ◽  
Water Transport ◽  
Chukchi Sea ◽  
Mesoscale Eddy ◽  
Late Summer ◽  
Ocean Model ◽  
Canada Basin ◽  
Pacific Water ◽  
Freshwater Transport ◽  
The Pacific

Abstract The process of the Pacific water transport in the Chukchi Sea and the southern Canada Basin is investigated by using an eddy-resolving coupled sea ice–ocean model. The simulation result demonstrates that the Pacific water flows into the basin by mesoscale baroclinic eddies, which are generated and developed as a result of the instability of a narrow and intense jet through the Barrow Canyon. Each eddy has a baroclinic anticyclonic structure, and its horizontal and vertical scales grow up by being merged with other ones during August and September, they separate into anticyclones whose diameters are about 50 km in October, and then they gradually shrink in early winter. The Pacific water transport across the Beaufort shelf break reaches maximum (about 0.3 Sv, where 1 Sv ≡ 106 m3 s−1) during late summer and early autumn when the eddy activities are enhanced. The sensitivity experiments indicate that the shelf-to-basin transport differs depending on the sea ice condition in the Chukchi Sea during summer. The difference is found to be associated with the jet strength, which is closely related to the location of the sea ice margin. When the sea ice margin is located in the Canada Basin, the jet is stronger, and mesoscale eddy activities and corresponding inflow of the Pacific water into the basin are enhanced. When sea ice remains in the shelf even in late summer, sea ice ocean stress plays a great role in braking the jet and the consequent suppression of the shelf-to-basin transport. The freshwater and heat transports into the basin associated with the Pacific water inflow depend on not only the volume flux but also on surface buoyancy flux in the shelf, which varies according to sea ice condition. The freshwater transport referenced to 34.8 psu is 259 km3 yr−1 in the medium sea ice extent case. Although the Pacific water becomes freshened as a result of its mixing with sea ice meltwater in the large extent case, the freshwater transport is still less than in the other cases. The heat transport is promoted by preferable absorption of solar heat in addition to energetic eddy-induced transport in the small extent case. The heat amount provided into the basin is equivalent to the reduction of sea ice thickness by about 1 m yr−1 north of the Chukchi and Beaufort shelf breaks.

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