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uniquorn

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1050 on: September 05, 2022, 11:34:50 PM »
Some papers on the current from Bering to Beaufort

2009
The western Arctic boundary current at 152°W: Structure, variability, and transport
Anna Nikolopoulos, Robert S. Pickart, Paula S. Fratantoni, Koji Shimada, Daniel J. Torres, E. Peter Jones
https://doi.org/10.1016/j.dsr2.2008.10.014

Quote
Abstract

From August 2002 to September 2004 a high-resolution mooring array was maintained across the western Arctic boundary current in the Beaufort Sea north of Alaska. The array consisted of profiling instrumentation, providing a timeseries of vertical sections of the current. Here we present the first-year velocity measurements, with emphasis on the Pacific water component of the current. The mean flow is characterized as a bottom-intensified jet of O (15 cm s−1) directed to the east, trapped to the shelfbreak near 100 m depth. Its width scale is only 10–15 km. Seasonally the flow has distinct configurations. During summer it becomes surface-intensified as it advects buoyant Alaskan Coastal water. In fall and winter the current often reverses (flows westward) under upwelling-favorable winds. Between the storms, as the eastward flow re-establishes, the current develops a deep extension to depths exceeding 700 m. In spring the bottom-trapped flow advects winter-transformed Pacific water emanating from the Chukchi Sea. The year-long mean volume transport of Pacific water is 0.13±0.08 Sv to the east, which is less than 20% of the long-term mean Bering Strait inflow. This implies that most of the Pacific water entering the Arctic goes elsewhere, contrary to expected dynamics and previous modeling results. Possible reasons for this are discussed. The mean Atlantic water transport (to 800 m depth) is 0.047±0.026 Sv, also smaller than anticipated.

Introduction

It is generally believed that the halocline of the interior Arctic Ocean is ventilated through lateral processes (Aagaard and Carmack, 1994). In the Canada Basin, the cold halocline source waters of Pacific origin are made saline and dense in wintertime through cooling and brine rejection on the Bering/Chukchi shelves (e.g., Muench et al., 1988; Weingartner et al., 1998). The precise means by which these waters then enter the interior basin remains unclear, however. Shelf-basin exchange is believed to take place through a variety of mechanisms. These include dense water plumes through canyons (Garrison and Becker, 1976), cross-stream wind-forced flow (Melling, 1993), and eddy formation (Manley and Hunkins, 1985). Direct evidence of such exchange, however, is largely lacking. Most of the mechanisms seem to involve, in one way or another, the presence of a boundary current along the edge of the shelf.

The first measurements of the subsurface circulation along the shelf edge and slope of the southern Canada Basin were made by Aagaard (1984). He observed a bathymetrically steered eastward flow, named the Beaufort Undercurrent, seaward of the 50 m isobath (northern edge unknown) between 146° and 152°W. Geostrophic shear calculations, in agreement with velocity observations, indicated an increased flow with depth down to at least 600 m. Aagaard (1984) postulated that the undercurrent extended from 50 m to as deep as 2500 m over a horizontal distance of 60–70 km, hence transporting Bering Sea, Chukchi Sea, and Atlantic water masses. In a later investigation Aagaard (1989) presented current measurements from two depths on the slope near 147°W, supporting the idea of an eastward current with its core located over the outer shelf. The flow was found to be negligible at 1000 m depth, but due to the coarse resolution of the current meters the precise location of the maximum and the vertical extent of the current could not be determined. Recently, Pickart (2004) investigated the circulation along the Alaskan Beaufort Sea shelf edge using historical hydrographic and current meter data collected between 1950 and 1987. Individual hydrographic cross-sections were combined to produce a section of mean geostrophic velocity, which was then referenced with the mean current meter data. This indicated the presence of a narrow (order 20 km) eastward current centered between 150 and 200 m depth. Pickart (2004) referred to this as the Beaufort shelfbreak jet. It was found to have three distinct seasonal configurations and to transport a significant fraction of the Bering Strait inflow.

Farther to the west, along the Chukchi Sea shelfbreak and slope, there is also evidence for an eastward-flowing boundary current. Although no mean sections have been constructed, individual synoptic sections of absolute geostrophic velocity (under light to moderate winds) indicate the presence of a shelfbreak jet with a similar structure to that in the Beaufort Sea (Mathis et al., 2007; Llinas et al., 2008). What is the source of the shelfbreak current along the Chukchi and Beaufort Seas? Models suggest that the northward flow of Pacific water emanating from Bering Strait should turn eastward upon reaching the Chukchi shelf edge to form such a current (Winsor and Chapman, 2004; Spall, 2007). Observations indicate a strong flow of Pacific-origin water through Herald Canyon on the western Chukchi shelf (Woodgate et al., 2005a; Pickart, 2009a) and through Barrow Canyon on the eastern shelf (Münchow and Carmack, 1997; Pickart et al., 2005). A third branch of Pacific water on the shelf is believed to exist through the gap between Herald and Hanna Shoals, known as the Central Channel (Woodgate et al., 2005a; Weingartner et al., 2005; Fig. 1). Presumably, these branches feed the current along the shelf edge of the Chukchi/Beaufort Seas.


2014
Seasonal to interannual variability of the Pacific water boundary current in the Beaufort Sea
Eric T. Brugler, Robert S. Pickart, G.W.K. Moore, Steven Roberts, Thomas J. Weingartner, Hank Statscewich
https://doi.org/10.1016/j.pocean.2014.05.002

Quote
Highlights

    The Pacific water boundary current has a maximum transport in summer.

    Over the past decade the transport of the boundary current has decreased by more than 80%.

    An increase in summer easterly winds along the Beaufort slope is the primary cause for the reduction in transport.

    The enhanced easterly winds are due to an intensification of the Beaufort High and deepening of the Aleutian Low.

    In recent years heat has been advected directly out of Barrow Canyon into the Canada Basin, contributing to sea ice melt.


Abstract

Between 2002 and 2011 a single mooring was maintained at the core of the Pacific water boundary current in the Beaufort Sea, approximately 150 km east of Pt. Barrow, Alaska. Using velocity and hydrographic data from six year-long deployments, we examine the variability of the current on seasonal to interannual timescales. The seasonal signal is characterized by enhanced values of volume, heat, and freshwater transport during the summer months associated with the presence of two summertime Pacific water masses, Alaskan Coastal Water and Chukchi Summer Water. Strikingly, over the decade the volume transport of the current has decreased by more than 80%, with comparable reductions in the heat and freshwater transports, despite the fact that the flow through Bering Strait has increased over this time period. The largest changes in the boundary current have occurred in the summer months. Using atmospheric reanalysis fields and weather station data, we demonstrate that an increase in summer easterly winds along the Beaufort slope is the primary cause for the reduction in transport. The stronger winds are due to an intensification of the summer Beaufort High and deepening of the summer Aleutian Low. Using additional mooring and shipboard data in conjunction with satellite fields, we investigate the implications of the reduction in transport of the boundary current. We argue that a significant portion of the mass and heat passing through Bering Strait in recent years has been advected out of Barrow Canyon into the interior Canada Basin – rather than entering the boundary current in the Beaufort Sea – where it is responsible for a significant portion of the increased sea ice melt in the basin.


2016
AON: Monitoring the Western Arctic Boundary Current in a Warming Climate
   Robert Pickart   Woods Hole Oceanographic Institution
http://resp.llas.ac.cn/C666/handle/2XK7JSWQ/69383

Quote
As Earth's climate has warmed over the past few decades, our planet has experienced a multitude of profound changes. Nowhere have the changes been more pronounced, nor happened as quickly, as in the Arctic Ocean. Pack-ice is melting, water is warming, storms are becoming stronger and more frequent, and basic circulation patterns are being altered. Our project focuses on the fate of the Pacific water that enters the Arctic Ocean through the Bering Strait. Pacific water plays a critical role in the western Arctic ecosystem. In wintertime the cold inflowing water provides nutrients that spur the growth of phytoplankton at the base of the food chain. In summertime, the warm water melts pack ice and provides freshwater to the Arctic Ocean. After the water crosses the Chukchi Sea, north of Bering Strait, some of it forms a narrow current at the edge of the shelf and flows eastward. As part of our project we will continue to maintain a mooring positioned in the center of the current to measure its physical and biological properties. The mooring has been deployed (with a few gaps) since 2002, and during this time it has measured striking changes that need to be placed in the context of the evolving Arctic system. In addition, we will carry out shipboard surveys of the current and adjacent waters when we service the mooring, to provide a larger-scale view of the fate of the Pacific water.

The monitoring mooring is situated at 152oW near the Beaufort Sea shelf break, roughly 150 km downstream of Pt. Barrow. It will be deployed for two years from fall 2016 to fall 2018. This will extend the time series at this location to 13 years. The mooring records the velocity of the water column and pack ice using two ADCPs, and measures temperature, salinity, and pressure using a series of MicroCats spaced along the wire. Chlorophyll fluorescence and nitrate will be measured at 35 m (at the top float of the mooring), and a passive acoustic recorder situated near the base of the mooring will record marine mammal calls. Zooplankton concentration will be estimated using the ADCP backscatter data. Among other things, this will allow us to determine how much water, heat, nutrients, chlorophyll, and freshwater are transported by the current, and, importantly, assess how much exchange occurs between the interior of the Arctic Ocean and the boundary waters. Upwelling occurs during all seasons along the Beaufort slope, and it appears to be increasing as the climate warms. The mooring is ideally suited to quantify the upwelling, as well any downwelling that occurs. The shipboard sampling will include sampling of some of the Distributed Biological Observatory transects, which will contribute to those ongoing time series.
« Last Edit: September 05, 2022, 11:59:04 PM by uniquorn »

uniquorn

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1051 on: September 05, 2022, 11:43:54 PM »
Why not go deeper...

The Atlantic Water Boundary Current in the Chukchi Borderland and Southern Canada Basin
Jianqiang Li, Robert S. Pickart, Peigen Lin, Frank Bahr, Kevin R. Arrigo, Laurie Juranek, Xiao-Yi Yang
First published: 27 July 2020
https://doi.org/10.1029/2020JC016197

Quote
Abstract

Synoptic shipboard measurements, together with historical hydrographic data and satellite data, are used to elucidate the detailed structure of the Atlantic Water (AW) boundary current system in the southern Canada Basin and its connection to the upstream source of AW in the Chukchi Borderland. Nine high-resolution occupations of a transect extending from the Beaufort shelf to the deep basin near 152°W, taken between 2003 and 2018, reveal that there are two branches of the AW boundary current that flow beneath and counter to the Beaufort Gyre. Each branch corresponds to a warm temperature core and transports comparable amounts of Fram Strait Branch Water between roughly 200–700 m depth, although they are characterized by a different temperature/salinity (T/S) structure. The mean volume flux of the combined branches is 0.87 ± 0.13 Sv. Using the historical hydrographic data, the two branches are tracked upstream by their temperature cores and T/S signatures. This sheds new light on how the AW negotiates the Chukchi Borderland and why two branches emerge from this region. Lastly, the propagation of warm temperature anomalies through the region is quantified and shown to be consistent with the deduced circulation scheme.

Plain Language Summary

Warm water flows into the Arctic Ocean from the North Atlantic and circulates counterclockwise through the different subbasins of the Arctic. The water is cooled, freshened, and densified as part of the global overturning circulation. The warm water also spreads into the interior Arctic with the potential to melt sea ice. Presently, very little is known about the Atlantic Water (AW) circulation in the Canada Basin, far from the source of the water. In this study, we analyze nine repeat shipboard transects extending from the Beaufort Sea shelf to the deep basin, taken between 2003 and 2018. The transects reveal that there are two branches of the AW boundary current, each characterized by a warm temperature core. The branches transport roughly equal amounts of water. Using an extensive historical database, we demonstrate that the two branches emerge from a region of complex topography known as the Chukchi Borderland. A single AW current entering the Borderland undergoes a series of divisions and merges, which ultimately forms two branches that are further distinguishable by their temperature and salinity structure. Finally, we document the propagation of warm temperature pulses through the region, which is consistent with the deduced circulation scheme.

Brigantine

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1052 on: September 13, 2022, 10:55:45 AM »
DMI satellite sea surface temps. I adjusted the scale to increase the contrast around 0⁰
#6

Brigantine

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1053 on: September 22, 2022, 03:38:39 PM »
DMI satellite sea surface temps. I adjusted the scale to increase the contrast around 0⁰
#7 - Two days before equinox

vox_mundi

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1054 on: September 29, 2022, 03:39:49 PM »
Researchers Identify Mechanism Responsible for Temperature and Salinity 'Staircases' In Arctic Ocean
https://phys.org/news/2022-09-mechanism-responsible-temperature-salinity-staircases.html

Researchers at the University of Toronto have identified the mechanism responsible for the formation of temperature and salinity "staircases" in the Arctic Ocean, resolving a mystery that has confounded oceanographers and climatologists alike for more than half a century.

The findings reported in Physical Review Fluids—which have attracted significant positive response from the research community—fully verify a previous analysis by the same authors published in the Journal of Fluid Mechanics in 2020 that documented the existence of this new hydrodynamic instability. The verification was accomplished by designing a series of direct numerical simulations of turbulence in the Arctic Ocean to better understand global ocean circulation.



The research builds on previous work that focused on understanding global ocean circulation under the ice age conditions from 30,000 to 70,000 years ago.

In the previously developed model of glacial climate, the rapid transitions from cold to warm weather were shown to be caused by an extensive "hole" in the sea ice cover of the North Atlantic Ocean resulting from heat flow out of the ocean into the sea ice. The magnitude of this heat flow was determined by the assumption that a staircase had formed in the ocean below.

Yuchen Ma et al, Thermohaline-turbulence instability and thermohaline staircase formation in the polar oceans, Physical Review Fluids (2022).
https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.7.083801
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Brigantine

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1055 on: October 01, 2022, 02:57:39 AM »
DMI satellite sea surface temps. I adjusted the scale to increase the contrast around 0⁰
#8 - Six days after equinox

Brigantine

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1056 on: October 07, 2022, 09:46:16 AM »
DMI satellite sea surface temps. I adjusted the scale to increase the contrast around 0⁰
#9

I figured out how to get the same thing faster in Copernicus. Unlike Mercator Ocean, you can define the end-points of the colour scale and get the contrast you want

1) Copernicus.. ⁻15⁰C - ⁺10⁰C (to show that it's the same data)
2) DMI rescaled ⁻15⁰C - ⁺10⁰C
3) Copernicus _ ⁻15⁰C -- ⁻1⁰C (focus ice surface)
4) Copernicus __ ⁻1⁰C -- ⁺10⁰C (focus water surface)
« Last Edit: October 07, 2022, 10:15:31 AM by Brigantine »

uniquorn

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1057 on: October 07, 2022, 08:04:49 PM »
Nice, never seen that comparison before. Clicking on the share button gives options to save as a time animation

Glen Koehler

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1058 on: October 09, 2022, 07:36:14 PM »
Not sure of best thread for this, please move as needed:
Interesting Arctic cloud cover quote from RealClimate article -

     "Kininmonth also explains the warming in the Arctic in terms of increased latent heat transfer from lower latitudes. It’s interesting that he needs to invoke both a slowdown and a speed-up of heat transport from the tropics to higher latitudes this way, and this complicates his concept. And if this were true, then we would expect to see increased cloud cover (and increased precipitation) there. Cloud cover has increased over limited areas where the ice has retreated, but this increase seems to be related to local moisture sources and probably not from increased storm activity or water vapour coming from low latitudes. "
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uniquorn

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1059 on: October 18, 2022, 10:30:04 PM »
DMI
3) Copernicus _ ⁻15⁰C -- ⁻1⁰C (focus ice surface)
4) Copernicus __ ⁻1⁰C -- ⁺10⁰C (focus water surface)

Just checking cmems sat against buoy data. 6C from surface to 56m depth just off south island. Just a touch warmer than 2020

Note: Click on the share icon to get a short url.
https://myocean.marine.copernicus.eu/-/amxk4sretx
« Last Edit: October 18, 2022, 10:44:47 PM by uniquorn »

Brigantine

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1060 on: October 18, 2022, 11:03:13 PM »
Good idea

I have had the impression before (from the DMI page) that those satellite-observed surface temps can be affected by clouds. Things change a lot day to day and then settle down where they were earlier. Ideally I'd want to use a 5-day median or something

That spot in the eastern Barents looks like it was snowing recently (indicating cloud presence) and the history from the 2 prior days fits the same pattern

uniquorn

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1061 on: October 27, 2022, 11:33:25 PM »
overlay today's ice in WSC onto red bathy.
click for defaults

gerontocrat

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1062 on: March 03, 2023, 05:53:58 PM »
Effect of reducing sea ice on Wave Power & Winds

This link https://www.nature.com/articles/s41598-023-29692-9 is to a paper that looked at winter sea ice in the Okhotsk Sea to establish whether wave power (Pw) increased as a result of reducing sea ice and increased winds.

The answer is yes, and that the increase in winds is also linked to the reduction in sea ice cover. Given that increased wave power increases breakup of the ice pack and erosion of the ice edge I think that this is yet  another positive feedback to add to the rather long catalog that can be assumed to happen in other marginal sea ice areas.

Increase in the wave power caused by decreasing sea ice over the Sea of Okhotsk in winter
Quote
Introduction
There is a great concern that ocean surface waves will increase due to the decrease in sea ice in SO (Sea of Okhotsk). However, to the best of our knowledge, previous studies have not yet focused on the SO and not evaluated the long-term trends of ocean surface waves, although several studies have been conducted in the Arctic Sea.

Therefore, the present study aimed to evaluate the long-term trends of wave fields in the SO for 40 years and reveal the quantitative contributions of the surface winds and sea ice to the long-term trends.

Recently, rather than wave height, Pw is also attracting attention as an indicator of the long-term behavior of the wave condition because it represents wave energy accumulated over different months, seasons, and years. For example, coastal inundation, erosion, and flooding depend not only on the wave height but also on wave period. Therefore, the present study focused on Pw
as an indicator of the long-term trends of ocean surface waves

Conclusions
Pw showed a significantly positive trend (approximately 12–15% per decade) during winter (December–February) in the SO. This positive Pw trend was predominantly caused by the strengthened Hs.

Additionally, on comparing the model simulations with original sea ice data (daily or hourly data) and climatological sea ice data, a positive trend of Pw was found to be enhanced by the reduction in the sea ice (reduction of direct wave attenuation due to the sea ice) and the increase in the surface wind.

The reduction of sea ice also strengthened the surface wind due to the increase in the horizontal gradient of SLP. The findings of the present study suggested that the reduction in the sea ice is majorly responsible for the increase in Pw during winter.

Studies that quantitatively examine the effects of surface wind and sea ice separately on long-term wave climate are rare, even if other sea ice areas are included. We believe that the wave–sea ice–atmosphere interaction shown in this study can improve our understanding of past, present, and future wave climates in the marginal ice zone.

click image to enlarge, click again for fullsize
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uniquorn

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1063 on: April 03, 2023, 03:38:23 PM »
mercator modelled salinity at 40m depth, 2021-2023.

Lower salinity water still pushing towards the Fram Strait.


uniquorn

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1064 on: April 03, 2023, 03:45:46 PM »
mercator modelled vertical velocity (upwelling and downwelling) at 40m, jul2022-mar2023

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1065 on: April 04, 2023, 06:20:58 AM »
    Good stuff as usual Uniquorn.  My perception of the CAA was of a static ice-land matrix until late summer melt.  But those animations show that under the ice the water is active.  Which makes me wonder about possible emergence of CAA-garlic press export in future years as the CAA melts out earlier in summer, which seems likely to occur given its latitude.
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Re: Arctic Ocean salinity, temperature and waves
« Reply #1066 on: April 05, 2023, 07:14:49 PM »
Modelled velocity and salinity for the last three days from

uniquorn

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1067 on: April 05, 2023, 09:06:38 PM »
Modelled velocity and salinity for the last three days from
Been looking at that. Mercator models some of the WSC eddying its way across the Fram Strait and continuing along the N Greenland coast.

johnm33

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1068 on: April 06, 2023, 12:08:59 AM »
Funny that, I thought that to some degree it showed the 'Atlantic' layer moving south towards Fram and then, as I would expect, it loses ground to the rotating frame and moves towards and across the CAA. That at least makes some physical sense to me, perhaps the WSC across N. Greenland is induced as and when tides etc. align. ++[ I should say I suspect the current across N.Greenland runs somewhat deeper, both just above and below the cill level beneath Lincoln. That would imply both the circulating Atl. layer and tides have a hand in the induction. ]++
As to flowing down to Peterman I was thinking a change of pace in the melt there would be an indicator of when [if] the WSC replaced the Atl. layer and couldn't face the prospect of chasing that down, thinking it could have been any time in the last 20 odd years, but Gero. put a link on that thread that suggests it may have been as recent as 2016, iirc. So perhaps a year or so before that maybe.
I switched sides and took a look at the last year trying to get an impression of how consistent the flow in was on the Pacific side.
« Last Edit: April 06, 2023, 10:19:29 AM by johnm33 »

uniquorn

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1069 on: April 06, 2023, 06:43:41 PM »
Quote
I thought that to some degree it showed the 'Atlantic' layer moving south towards Fram and then, as I would expect, it loses ground to the rotating frame and moves towards and across the CAA. That at least makes some physical sense to me, perhaps the WSC across N. Greenland is induced as and when tides etc. align. ++[ I should say I suspect the current across N.Greenland runs somewhat deeper, both just above and below the cill level beneath Lincoln. That would imply both the circulating Atl. layer and tides have a hand in the induction. ]++

Tend to agree that returning Arctic water entering the Nares makes more sense and the arrows northwest of Greenland support that.
 Looking below at 142m depth, nearer the bottom of the WSC, there's no indication of temperature crossing the Fram Strait so maybe the WSC doesn't make it directly over but could perhaps drift back from the Yermak Plateau.. This is all modelled though.

vox_mundi

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1070 on: February 06, 2024, 02:16:19 PM »
Frequent Marine Heat Waves In the Arctic Ocean Will Be the Norm, Says New Study
https://phys.org/news/2024-02-frequent-marine-arctic-ocean-norm.html



Since 2007, conditions in the Arctic have shifted, as confirmed by data recently published in the journal Communications Earth & Environment. Between 2007 and 2021, the marginal zones of the Arctic Ocean experienced 11 marine heat waves, producing an average temperature rise of 2.2 degrees Celsius above seasonal norm and lasting an average of 37 days. Since 2015, there have been Arctic marine heat waves every year.

The most powerful heat wave to date in the Arctic Ocean was in 2020; it continued for 103 days, with peak temperatures that were four degrees Celsius over the long-term average. The probability of such a heat wave occurring without the influence of anthropogenic greenhouse gases is less than 1%, as calculated by Barkhordarian's team at the Cluster of Excellence CLICCS. By doing so, they have narrowed down the number of plausible climate scenarios in the Arctic. According to the study, annual marine heat waves will be the norm.

In the study, Barkhordarian also proves for the first time that heat waves are produced when sea ice melts early and rapidly after the winter. When this happens, considerable heat energy can accumulate in the water by the time maximum solar radiation is reached in July.

Officially, it is considered to be a marine heat wave when temperatures at the water's surface are higher than 95% of the values from the past 30 years for at least five consecutive days.

"Not just the constant loss of sea ice but also warmer waters can have dramatic negative effects on the Arctic ecosystem," says Barkhordarian. Food chains could collapse, fish stocks could be reduced, and overall biodiversity could decline

Arctic marine heatwaves forced by greenhouse gases and triggered by abrupt sea-ice melt, Communications Earth & Environment (2024)
https://dx.doi.org/10.1038/s43247-024-01215-y
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morganism

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1071 on: March 03, 2024, 09:39:43 PM »
Ilulissat Icefjord Upper-Layer Circulation Patterns Revealed Through GPS-Tracked Icebergs



The Greenland Ice Sheet has undergone rapid mass loss over the last four decades, primarily through solid and liquid discharge at marine-terminating outlet glaciers. The acceleration of these glaciers is in part due to the increase in temperature of ocean water in contact with the glacier terminus. However, quantifying heat transport to the glacier through fjord circulation can be challenging due to iceberg abundance, which threatens instrument survival and fjord accessibility. Here we utilize iceberg movement to infer upper-layer fjord circulation, as freely floating icebergs (i.e., outside the mélange region) behave as natural drifters. In the summers of 2014 and 2019, we deployed transmitting GPS units on a total of 13 icebergs in Ilulissat Icefjord, an iceberg-rich and historically data-poor fjord in west Greenland, to quantify circulation over the upper 0–250 m of the water column. We find that the direction of upper-layer fjord circulation is strongly impacted by the timing of tributary meltwater runoff, while the speed of this circulation changes in concert with glacier behavior, which includes increases and decreases in glacier speed and meltwater runoff. During periods of increased meltwater runoff entering from tributary fjords, icebergs at these confluences deviated from their down-fjord trajectory, even reversing up-fjord, until the runoff pulse subsided days later. This study demonstrates the utility of iceberg monitoring to constrain upper-layer fjord circulation, and highlights the importance of including tributary fjords in predictive models of heat transport and fjord circulation.
Key Points

    We used 13 on-iceberg GPS units to constrain upper-layer (0–250 m) circulation in Ilulissat Icefjord, west Greenland

    Deviations in down-fjord iceberg trajectory coincide with tributary meltwater flux, in both location and timing

    The speed of upper-layer circulation changes in concert with glacier behavior, including glacier speed and meltwater runoff

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023JC020117

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Re: Arctic Ocean salinity, temperature and waves
« Reply #1072 on: March 03, 2024, 10:09:42 PM »
How melting Arctic ice leads to European drought and heatwaves
Fresh, cold water from Greenland ice melting upsets North Atlantic currents.

The Arctic Ocean is mostly enclosed by the coldest parts of the Northern Hemisphere’s continents, ringed in by Siberia, Alaska and the Canadian Arctic, with only a small opening to the Pacific through the Bering Strait, and some narrow channels through the labyrinth of Canada’s Arctic archipelago.

But east of Greenland, there’s a stretch of open water about 1,300 miles across where the Arctic can pour its icy heart out to the North Atlantic. Those flows include increasing surges of cold and fresh water from melted ice, and a new study in the journal Weather and Climate Dynamics shows how those pulses can set off a chain reaction from the ocean to the atmosphere that ends up causing summer heatwaves and droughts in Europe.

The large new inflows of fresh water from melting ice are a relatively new ingredient to the North Atlantic weather cauldron, and based on measurements from the new study, a currently emerging “freshwater anomaly” will likely trigger a drought and heatwave this summer in Southern Europe, said the study’s lead author, Marilena Oltmanns, an oceanographer with the United Kingdom’s National Oceanography Centre.

She said warmth over Greenland in the summer of 2023 melted a lot of ice, sending more freshwater toward the North Atlantic. Depending on the exact path of the influx, the findings suggest that, in addition to the immediate impacts this year, it will also trigger a heatwave and drought in Northern Europe in a more delayed reaction in the next five years, she said.
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The coming extremes will probably be similar to the European heatwaves of 2018 and 2022, she added, when there were huge temperature spikes in the Scandinavian and Siberian Arctic, as well as unusual wildfires in far northern Sweden. That year, much of the Northern Hemisphere was scorched, with “22 percent of populated and agricultural areas simultaneously experiencing heat extremes between May and July,” according to a 2019 study in Nature.
(more)

https://arstechnica.com/science/2024/03/how-melting-arctic-ice-leads-to-european-drought-and-heatwaves/#p3


European summer weather linked to North Atlantic freshwater anomalies in preceding years

Amplified Arctic ice loss in recent decades has been linked to the increased occurrence of extreme mid-latitude weather. The underlying mechanisms remain elusive, however. One potential link occurs through the ocean as the loss of sea ice and glacial ice leads to increased freshwater fluxes into the ocean. Thus, in this study, we examine the link between North Atlantic freshwater anomalies and European summer weather. Combining a comprehensive set of observational products, we show that stronger freshwater anomalies are associated with a sharper sea surface temperature front between the subpolar and the subtropical North Atlantic in winter, an increased atmospheric instability above the sea surface temperature front, and a large-scale atmospheric circulation that induces a northward shift in the North Atlantic Current, strengthening the sea surface temperature front. In the following summer, the lower-tropospheric winds are deflected northward along the enhanced sea surface temperature front and the European coastline, forming part of a large-scale atmospheric circulation anomaly that is associated with warmer and drier weather over Europe. The identified statistical links are significant on timescales from years to decades and indicate an enhanced predictability of European summer weather at least a winter in advance, with the exact regions and amplitudes of the warm and dry weather anomalies over Europe being sensitive to the location, strength, and extent of North Atlantic freshwater anomalies in the preceding winter

https://wcd.copernicus.org/articles/5/109/2024/