Tag Archives: science

Scoresby Sund – Greenland’s Longest Fjord

Fog, fog, and more fog is all we saw as we approached Scoresby Sund aboard the German research ship Maria S. Merian from Denmark Strait to the south-east. The fog lifted as soon as we passed Kap Brewster and began work on ocean currents and waters at the entrance of this massive fjord system. My artist friend and wife Dragonfly Leathrum posted a wonderful travel essay with many photos that did not include these:

We were here to explore how the coastal ocean off Greenland may relate to Daugaard-Jensen Gletscher at the head of the fjord some 360 km away (195 nautical miles or about a day of constant steaming at 8 knots). This tidewater glacier discharges as much icy mass out to sea as does Petermann Gletscher or 79N Glacier to the north or half as much as Helheim, Kangerdlugssuaq, and Jacobshavn Glaciers to the south. Unlike all those other glaciers, Daugaard-Jensen and its fjord are still largely unexplored.

Location Map of Scoresby Sund. Kap Brewster is at bottom right while Daugaard-Jensen Gletscher 360 km away is near the top left.

Location Map of Scoresby Sund. Kap Brewster is at bottom right while Daugaard-Jensen Gletscher 360 km away is near the top left.


Part of the chart of the East Greenland coast drawn up by William Scoresby Jr. in 1822, showing the numerous features that he names in Liverpool land (Liverpool Coast) and adjacent areas. From: Scoresby (1823)

Part of the chart of the East Greenland coast drawn up by William Scoresby Jr. in 1822, showing the numerous features that he names in Liverpool land (Liverpool Coast) and adjacent areas. From: Scoresby (1823)


While the entrance between Kap Tobin and Kap Brewster was known to whalers in the early 19th century, it was William Scoresby Sr. after whom the fjord is named. His scientist son William Scoresby Jr. mapped coastal Greenland between 69.5 and 71.5 North latitude during his last voyage in 1822. Nobody entered the fjord until 1891 when Lt. Carl Ryder of the Danish Navy sailed deep into the fjord to explore the area for a year with 10 companions. They built a hut next to a natural port that they named Hekla Harbor. Amazingly, they also measured ocean temperature profiles almost every month from the surface to 400 m depth. I found these data at the National Ocean Data Center of the United States Government.

Ocean temperature (left panel) and salinity (right panel) as it varies with depth in different years. Blue represents measurements from 1891/92, red from 1990, and black from 2018.

Ocean temperature (left panel) and salinity (right panel) as it varies with depth in different years. Blue represents measurements from 1891/92, red from 1990, and black from 2018.

Searching for data from Scoresby Sund, I found 17 profiles of water temperature with data from at least 10 depths. Funny that 12 of these profiles were collected in 1891 and 1892 while the other 5 profile contain salinity measurements made in 1933, 1984, 1985, 1988, and 2002. The 1988 cast was taken by an Icelandic vessel and also contained continous data from a modern electronic sensor rather than waters collected by bottles. I “found” another 4 modern sensor profiles collected in 1990 at the Alfred-Wegener Institute in Germany.

That’s pretty much “it” … until we entered the fjord in 2018 when we collected another 27 casts thus more than doubling the ocean profiles. More exciting, though, is the very large shift in ocean temperatures from 1990 to 2018. The 1990 temperatures are very similar to the 1891/92 temperatures, but all old temperatures (also from 1933 and 1985, not shown) are all about 1 degree Celsius (2 degrees Fahrenheit) warmer than those we measured in 2018. Why is this so? Does such warming originate from outside the fjord? If so, how does the warmer Atlantic water at depth in deep water crosses the 80 km wide shallow continental shelf to enter Scoresby Sund? Are any of these ideas supported by actual data? What data are there?

Ocean data location off eastern Greenland collected from 1890 to 2010 that reside in NODC archives. Red are water bottle data while yellow are modern electronic sensor measurements. The white box bottom left is the entrance to Scoresby Sund. Light blue areas are water less than 500 m deep while dark blue shades are deeper than 1000 m.

Ocean data location off eastern Greenland collected from 1890 to 2010 that reside in NODC archives. Red are water bottle data while yellow are modern electronic sensor measurements. The white box bottom left is the entrance to Scoresby Sund. Light blue areas are water less than 500 m deep while dark blue shades are deeper than 1000 m.

Discoveries in science can be pretty basic, if one is at the right location at the right time with the right idea. Also, there is more data to the south that I did not yet look at to investigate the question of what causes the warming of bottom waters in Scoresby Sund.

 

Petermann Glacier & Videos & Science

I just re-discovered four stunning science videos from the last expedition to reach Petermann Gletscher in Greenland. Each video is 3-6 minutes long and was made professionally by Saskia Madlener of 77th Parallel Productions with partial support from the US National Science Foundation. They were first posted at

https://petermannsglacialhistory.wordpress.com/videos/

and relate to a joint 2015 US-Swedish Expedition. The project involved diverse groups of geological, physical, biological, and chemical scientists from Sweden, England, Scotland, Denmark, Germany, Canada, and the USA who all worked together aboard the Swedish icebreaker Oden for 6 weeks. [For full resolution HD video click on the Vimeo icon in the video.]

Petermann Glacier 2015 – Overview from 77th Parallel on Vimeo.

Petermann Glacier 2015 – Ocean & Ice from 77th Parallel on Vimeo.

Petermann Glacier 2015 – Rocks & Shells from 77th Parallel on Vimeo.

Petermann Glacier 2015 – Expedition from 77th Parallel on Vimeo.

What’s happened at Petermann Gletscher since the Industrial Revolution 150 years ago?

More than 15 years ago I first set sight on the floating Petermann Gletscher when the United States’ Coast Guard Cutter Healy visited north-west Greenland for the first time on 10th August of 2003. We only had to sail 20 km into the fjord to reach a flat expanse of glacier ice that stuck less than 5 m (15 feet) above the sea. In 2012 and 2015 we had to sail another 20 km, because two large calving events had shortened the glacier farther back than it has since first records were kept in 1876. The terminus was also much higher, almost 25 m (75 feet) above the sea:

DSCN4444

Terminus of Petermann Gletscher 5th August 2015 from aboard the Swedish icebreaker Oden. View is to the south-east. [Photo Credit: Andreas Muenchow]

I published more detailed results on observed glacier change and estimated melt rates with Drs. Laurie Padman and Helen Fricker in the Journal of Glaciology from which I take these two figures:

Muenchow2014_01

Petermann Gletscher’s two large calving events in 2010 and 2012 as seen from MODIS satellite. The glacier is floating on the ocean seaward of the grounding line indicated by the thick black line. Black areas are open ocean water, white is ice. Adapted from Muenchow et al., 2014.

Muenchow2014_02

Time series from 1876 to 2014 of the length of Petermann Gletscher as measured from its grounding line at y=0 km. Triangles are observations while lines indicate a steady 1 km per year advance. The insert shows three maps of observed glacier shapes. From Muenchow et al., 2014.

Back in 2003 the glacier advanced about 1 km each year and it does so still. Almost the same, but not exactly, because the removal of 6 “Manhattans” in 2010 and 2012 increased the forward speed some, that is, the glacier now moves faster forward than it did before. Many sensors placed on the glacier measured this speeding, but the glacier also gets thinner as it speeds up. It is stretched thin. I published this back in 2016 together with Drs. Laurie Padman, Keith Nicholls, and my PhD student Peter Washam in Oceanography:

Muenchow2016_03

Speed at which Petermann Gletscher moves out into the sea from many different measurements. The glacier moves more slowly over land (negative distances) than it does floating over the ocean (positive distances). Estimates made after 2012 are about 10-20 % higher than RADARSAT estimates before that date. From Muenchow et al., 2016.

With substantial help from the British Antarctic Survey we installed in 2015 a small ocean observing system under the floating glacier. It transmitted data from 800 meters (2400 feet) below the 100 m (300 feet) thick glacier ice via cables connected to a weather station. We sucessfully repaired the station (as well as a Danish weather station nearby) that stopped transmitting data via satellites in 2016. Two journalists of the Washington Post, Chris Mooney and Whitney Shefte joined Keith Nicholls and myself. Their outstanding and accurate reporting of our work includes video and graphics for a wider audience that you can find at this link:

Washington Post Video of 2016 Petermann Gletscher Site Visit

The ocean and glacier data were worked over carefully by Peter Washam who defended his dissertation last month. Dr. Washam moved to Georgia Tech in Atlanta to work with Dr. Britney Schmidt whose interests relate to the ice-covered oceans below some moons of Jupiter. Peter connected ocean temperature and salinity with ice radar and remote sensing data to estimate how much the glacier is melted by the ocean and how the ocean does this. His main result will be published later this year in the Journal of Glaciology [Added July-12, 2019: Published online as Washam et al., 2019 at the Journal of Glaciology.], that is

“… This increase in basal melt rates confirms the direct link between summer atmospheric warming around Greenland and enhanced ocean-forced melting of its remaining ice shelves. We attribute this enhanced melting to increased discharge of subglacial runoff into the ocean at the grounding line, which strengthens under-ice currents and drives a greater ocean heat flux toward the ice base…”

The next large calving will be no surprise: Large fractures cross much of the glacier. They are visible about 10-20 km behind the current terminus and are discussed and closely monitored almost every day at the excellent site of Greenland Enthusiasts from all walks of life who post at

https://forum.arctic-sea-ice.net/index.php/topic,53.600.html

Furthermore, a new sophisticated computer model of Petermann Gletscher reveals that the loss of this large “still attached” ice island is already gone from the glacier in terms of the friction that it provides along the sidewalls. Another way of putting this, all it takes is a little wiggle or bump and the separation will become visible. Dr. Martin Rueckamp just published this study in the Journal of Geophysical Research.

There is much more to be explored with regard to Petermann. Here are some of the readings and writings that I have done with many fellow sailors through uncertain climates:

Johnson, H.L., A. Muenchow, K.K. Falkner, and H. Melling: Ocean circulation and properties in Petermann Fjord, Greenland. Journal of Geophysical Research, 116, doi:10.1029/2010JC006519, 2011. .pdf

Muenchow, A., L. Padman, and H.A. Fricker: Interannual changes of the floating ice shelf of Petermann Gletscher, North Greenland, from 2000 to 2012 Journal of Glaciology, 60, doi:10.3189/2014JoG13J135, 2014. .pdf

Muenchow, A., L. Padman, P. Washam, and K.W. Nicholls, 2016: The ice shelf of Petermann Gletscher, North Greenland and its connection to the Arctic and Atlantic Oceans, Oceanography, 29, 84-95, 2016. .pdf

Rueckamp, M, N. Neckel, S. Berger, A. Humbert, and V. Helm: Calving induced speed-up of Petermann Glacier, Journal of Geophysical Research, 124, 216-228, 2019. .pdf

Shroyer, E., L. Padman, R. Samelson, A. Muenchow, and L. Stearns: Seasonal control of Petermann Gletscher ice-shelf melt by the ocean’s response to sea-ice cover in Nares Strait, Journal of Glaciology, 63, doi:10.1017/jog.2016.140, 2017. .pdf

Washam, P., A. Muenchow, and K.W. Nicholls: A decade of ocean changes impacting the ice shelf of Petermann Gletscher, Greenland, Journal of Physical Oceanography, 48, 2477-2493, 2018. source

Washam, P., K.W. Nicholls, A. Muenchow, and L. Padman: Summer surface melt thins Petermann Gletscher ice shelf by enhancing channelized basal melt, Journal of Glaciology, 65, doi:10.1017/jog.2019.43, 2019. .pdf

America’s Self-Mutilation

I am an American and I am infuriated that my country’s government is (a) unable and unwilling to balance its books, (b) unable and unwilling to govern, because (c) a childish minority in Congress throws a temper tantrum, and (d) parental and political leadership fails to lead, guide, and compromise. The shut-down of the U.S. government only serves those who Continue reading

Women In Science: Costs and Benefits

“Science remains institutionally sexist. Despite some progress, women scientists are still paid less, promoted less frequently, win fewer grants and are more likely to leave research than similarly qualified men.” [Nature, Mar.-7, 2013]

This is from yesterday’s special issue of Nature which prompted this tongue-in-cheek comment by Prof. Dr. Cristina Archer:

Can we put a dollar amount to how much it would cost to fill the gender gap with respect to salary disparity?

Here is the procedure:

1) N_w = number of women scientists in the US
2) S_w = average salary of the N_w women scientists in the US
3) S_m = average salary of the male scientist in the US
4) Delta = difference in salary between male and female scientists
5) Tot = total dollars that the female scientists should be receiving to fill the disparity = Delta * N_w

To get a sense of the order of magnitude, here are some values:

1) N_w = 93,400 (in 2008, from the Nature paper)
2) S_w = $60,000 (this is actually the median, not the average, in 2008)
3) S_m= $84,000 (median in 2008)
4) Delta = $24,000
5) Tot = $24,000 * 93,400 = $2,241,600,000 (yes, billions)

For the nerdy of us, I acknowledge that using the median instead of the average might give an overestimate of the final bonus, although the order of magnitude is correct.

Since the gender gap seems very expensive to fill (~$2 billions), it might be cheaper and easier to actually reduce the salary of all male scientists (N_m = 179,400). The total saved would be:

Tot2 = $24,000 * 179,400 = $4.3B (of course billions)

If that money could be donated to NSF, the benefits to research in the US would be incalculable.

So … who wants to be the first male scientist to give up 28% of his salary and start filling the gender gap?

I admit, that I was the first to volunteer.

ADDENDUM: This post is not meant to criticize any institution in any way or form. The fact that these issues are discussed openly reflects both sensitivity and progress towards a common goal of gender equality in science. There is also a student’s perspective that Allison Einolf posted here last summer which includes references to a 2011 NSF study on the issue.