Atlantic Water Influence on Glacier Retreat

The warming of Atlantic Water along Greenland’s southeast coast has been considered a potential driver of glacier retreat in recent decades. In particular, changes in Atlantic Water circulation may be related to periods of more rapid glacier retreat. Further investigation requires an understanding of the regional circulation. The nearshore East Greenland Coastal Current and the Irminger Current over the continental slope are relatively well studied, but their interactions with circulation further offshore are not clear, in part due to relatively sparse observations prior to establishing the OOI Irminger Sea Array and the Overturning in the Subpolar North Atlantic Program (OSNAP).

[media-caption path="/wp-content/uploads/2022/04/Pioneer-highlight.png" link="#"]Satellite-derived sea surface temperature after adjustment for the Irminger Current (IC; green), Shelf Trough (ShTr; orange), and East Greenland Coastal Current (EGCC; purple). Monthly values (thin lines) are shown for 2000-2018 with 24-month low-passed records overlain. In situ observations from the fjord mouth (290 m: Black) and OOI flanking mooring FLMA (180 m; blue) are shown for comparison.[/media-caption]

In a recent study (Snow et al., 2021) use in-situ mooring data to validate satellite SST records and then use the 19-year satellite record to investigate relationships between glacier melt and Atlantic Water variability. In order to use the satellite records for this purpose, several adjustments must be made, including accounting for cloud and sea ice contamination, eliminating seasonally-varying diurnal biases, and removing the influence of air temperature. This adjusted satellite SST can be compared to in-situ mooring data during a portion of the record. A coastal mooring near the Sermilik Fjord mouth and the OOI Irminger Sea Array provide useful records during 2009-2013 and 2014-2018, respectively (Figure 24). An interesting aspect is that the temperature record from OOI Flanking Mooring A (FLMA) is useful for this purpose even though the measurements are at 180 m depth. This is because the upper ocean is relatively homogeneous in this region, and the mixed layer is deeper than 180 m during much of the year. The authors find that the adjusted satellite SST is consistent with the in-situ records on monthly to interannual time scales (Figure above). This provided the motivation to investigate relationships between the 19 year satellite record and glacier discharge rates.

The study concludes that warmer upper ocean temperatures as far offshore as the OOI Irminger Sea Array were concurrent with increased glacier retreat in the early 2000s, in support of the idea that Atlantic Water circulation plays a role. However, they also note that this influence is not direct, because of substantial variation in how Atlantic Water is diluted as it flows across the shelf towards Sermilik Fjord. The idea that time-varying dilution of Atlantic Water governs the temperature of water reaching the glacier was not previously understood, and resolving such small-scale, time-varying processes is a challenge for models. The authors conclude that with appropriate adjustments, “[satellite] SSTs show promise in application to a wide range of polar oceanography and glaciology questions” and that the method can be generalized to other glacier outflow systems in southeast Greenland to complement relatively sparse in-situ records.

Snow, T., Straneo, F., Holte, J., Grigsby, S., Abdalati, W., & Scambos, T. (2021). More than skin deep: Sea surface temperature as a means of inferring Atlantic Water variability on the southeast Greenland continental shelf near Helheim Glacier. J. Geophys. Res: Oceans, 126, e2020JC016509.

Read More

Pioneer Relocation Update 2021-09-29

The Pioneer Array, currently sited on the New England Shelf (NES), was conceived within OOI as a re-locatable, coastal array (OOI Science Plan, 2001; OOI Science Prospectus, 2007). At the Fall 2020 American Geophysical Union meeting, the National Science Foundation announced the start of a process for relocation of the Array.  After a variety of community engagement activities and two intensive Innovations Labs, it was determined that the Pioneer Array will be relocated to the southern Middle Atlantic Bight (MAB). Existing infrastructure, with some modifications, will be utilized to create a new Array to address compelling science questions at the new site.

The OOI Program is consolidating the community input and preparing for Pioneer relocation activities. The overall effort is complex, and will span roughly 30 months. In order to provide a window for these efforts within the existing operational budget, there will be a pause in Pioneer field activities. Preliminary plans are for the final recovery of the NES Pioneer Array in the fall of 2022 and the initial deployment of the MAB Array in the spring of 2024. The figure below shows the anticipated timeline, with three main phases. Phase 1 will focus on preparatory activities, including environmental and engineering assessments, and a study of regulatory requirements. During Phase 2, the bulk of the engineering and design effort will be conducted. During Phase 3, environmental compliance and permitting will be completed, along with the preparation of the infrastructure for deployment.




Read More

Irminger Array Successfully Turned 8th Time

The Irminger 8 Team successfully wrapped up the eighth turn of the Global Irminger Sea Array on 26 August when the R/V Neil Armstrong docked in Reykjavik, Iceland. After a few days of demobilization, the 10 members of the science party were free to head home after showing proof of a negative COVID test 72 hours before boarding a flight back to the U.S.

Chief Scientist John Lund led the science party of 10 in completing all of the expedition’s objectives. Over the course of 26 days at sea, they recovered four moorings and deployed four new moorings in their place. The team also deployed three gliders—two Open Ocean and one Profiling—and recovered a glider that had been in the water since 2020 and whose battery supply was rapidly depleting.

[media-caption path=”” link=”#”]The Irminger Sea presents challenges of high winds, strong waves, and icebergs as shown here with the R/V Neil Armstrong in the foreground. Credit: drone video, Croy Carlin SSSG. [/media-caption]

One highlight of the trip was engaging in scientific outreach with a class of fourth graders. The team connected with the students while out on the open ocean via Zoom. The oceanographers aboard the ship each had a chance to share what it’s like being on an oceanographic voyage and explain the purpose of the different instruments and sensors on the arrays. Another highlight of the expedition was the OOI team’s ongoing collaboration with OSNAP (Overturning in the Subpolar North Atlantic Program). While OSNAP participants were not onboard the Armstrong as in the past, their shore-based presence was clearly in evidence.  Expert hydrographer Leah McRaven worked with the onboard team to adjust CTD (Conductivity, temperature, depth) sampling to ensure that new CTD equipment was calibrated and sampling properly.

The science team also added a novel twist to the regular shipboard sampling that supports field calibration and validation of the platforms and sensors in the arrays. During Irminger 8, the shipboard team worked with OOI’s onshore data team to make collected CTD data available online in near real-time. As an added bonus, McRaven shared her insights about CTD sampling in regular blog posts here.

The Irminger 8 Team took full advantage of being in this critical ocean region, which is sensitive to climate change. During transit from Woods Hole to the array, off the southeast coast of Greenland, the team deployed surface drifters and ARGO floats for the Greenland Freshwater Project, which is studying the impact of freshwater runoff from Greenland’s melting ice sheet on the North Atlantic and Arctic climate. The team also deployed a biogeochemical ARGO float for the Global Ocean Biogeochemistry Project, and took a series of CTD casts on behalf of OSNAP, to add to long term data collection efforts in this critical region. In addition, the team deployed two RAFOS floats for the Madagascar Basin Project to measure deep water circulation and 15 Sofar Spotter buoys to measure wind, wave, and temperature data.

“In the ideal, science is a collaborative process,” said Chief Scientist John Lund. “During transit time to and from the array, we were able to help our scientific partners get their equipment in the water. The data provided will help advance understanding of this critically important region, which is equally difficult to sample. The region has high winds, large, steep waves, strong currents, icebergs, and consequent equipment icing.”

Given the challenges of the ocean environment at these latitudes, the eighth turn of Irminger Array included equipment improvements. The newly deployed surface moorings included wind turbine modifications to help it withstand strong, volatile winds, and it also incorporated other structural modifications to strengthen the mooring, while easing refurbishment. Similarly, design modifications were made to the subsurface moorings to help ensure consistent, long-term data collection.

The team experienced some of these challenges of high winds and strong waves while on the cruise, but the rough conditions were compensated by the gorgeous scenery of the region. Added Lund, “One afternoon, the sun came out as the ship transited further up Prince Christian Sound. Everyone was awed by the beauty of the landscape. We saw glaciers, icebergs and the occasional whale.”

Prior to leaving the Sound, the team secured all the items for the transit to Reykjavik, the demobilization of the ship, and finally the journey home to Woods Hole.




Read More

CGSN Infrastructure and Operations Webinar

In case you missed it, here’s another chance to join the leaders of the Coastal and Global Scale Node (CGSN) team to hear them describe the infrastructure making up the CGSN arrays, the current status of deployment, and how researchers and educators can get involved with the OOI.


[embed][/embed] Read More

CGSN Operations and Infrastructure Webinar

An informational webinar on the OOI Coastal and Global Scale Nodes (CGSN) will be presented on 15 September 2021 from 3:00-4:00 pm EDT. A presentation by the CGSN Team will be followed by a Q&A session.

Topics covered will include infrastructure making up the CGSN Arrays (Coastal Pioneer, Global Irminger Sea, and Global Station Papa), the current status of deployments, how to access near real-time data, and how to engage with the OOI.

Read More

CGSN Webinar 15 September

An informational webinar on the OOI Coastal and Global Scale Nodes (CGSN) will be presented on 15 September 2021 from 3:00-4:00 pm EDT. A presentation by the CGSN Team will be followed by a Q&A session.

Topics covered will include infrastructure making up the CGSN Arrays (Coastal Pioneer, Global Irminger Sea, and Global Station Papa), the current status of deployments, how to access near real-time data, and how to engage with the OOI.

Register here so you don’t miss out on the opportunity to meet the OOI CGSN Team and learn how you can work together.



Read More

A Case Study for Open Data Collaboration

Recognizing that freely accessible ocean observatory data has the potential to democratize interdisciplinary science for early career researchers, Levine et al. (2020) set out to demonstrate this capability using the Ocean Observatories Initiative.  Publicly available data from the OOI Pioneer Array moorings were used, and members of the OOI Early Career Scientist Community of Practice (OOI-ECS) collaborated in the study.

A case study was constructed to evaluate the impact of strong surface forcing events on surface and subsurface oceanographic conditions over the New England Shelf.  Data from meteorological sensors on the Pioneer surface moorings, along with data from interdisciplinary sensors on the Pioneer profiler moorings, were used.  Strong surface forcing was defined by anomalously low sea level pressure – less than three times the standard deviation of data from May 2015 – August 2018.  Twenty-eight events were identified in the full record.  Eight events in 2018 were selected for further analysis, and two of those were reported in the study (Figure 24).

[media-caption path="" link="#"]Figure 24. Two surface forcing events (16 and 27 November) identified from the time series of surface forcing at the Pioneer Central surface mooring.  Vertical lines indicate the peak of the anomalous low-pressure events (gray), as well as times 48 h before (red) and after (blue).  (A) sea level pressure, (B) wind speed, (C) air temperature, (D) latent (solid) and sensible (dashed) heat fluxes, (E) sea surface temperature, and (F) surface current speed and direction. [/media-caption]

The impact of surface forcing on subsurface conditions was evaluated using profile data near local noon on the day of the event, as well as 48 hr before and after (Figure 24). Subsurface data revealed a shallow (40-60 m) salinity intrusion prior to the 16 November event, which dissipated during the event, presumably by vertical mixing and concurrent with increases in dissolved oxygen and decreases in colored dissolved organic matter (CDOM). At the onset of the 27 November event, nearly constant temperature, salinity, dissolved oxygen and CDOM to depths of 60 m were seen, suggesting strong vertical mixing.  Data from multiple moorings allowed the investigators to determine that the response to the first event was spatially variable, with indications of slope water of Gulf Stream origin impinging on the shelf. The response to the second event was more spatially-uniform, and was influenced by the advection of colder, fresher and more oxygenated water from the north.

The authors note that the case study shows the potential to address various interdisciplinary oceanographic processes, including across- and along- shelf dynamics, biochemical interactions, and air-sea interactions resulting from strong storms. They also note that long-term coastal datasets with multidisciplinary observations are relatively few, so that the Pioneer Array data allows hypothesis-driven research into topics such as the climatology of the shelfbreak region, seasonal variability of Gulf Stream meanders and warm-core rings, the influence of extreme events on shelf biogeochemical response, and the influence of a warming climate on shelf exchange.

In the context of the OOI-ECS, the authors note that the study was successfully completed using open-source data across institutional and geographic boundaries, within a resource-limited environment.  Interpretation of results required multiple subject matter experts in different disciplines, and the OOI-ECS was seen as well-suited to “team science” using an integrative, collaborative and interdisciplinary approach.



Levine, RM, KE Fogaren, JE Rudzin, CJ Russoniello, DC Soule, and JM Whitaker (2020) Open Data, Collaborative Working Platforms, and Interdisciplinary Collaboration: Building an Early Career Scientist Community of Practice to Leverage Ocean Observatories Initiative Data to Address Critical Questions in Marine Science. Front. Mar. Sci. 7:593512. doi: 10.3389/fmars.2020.593512.

Read More