Huang Jie

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  • Article
    Sources and upstream pathways of the densest overflow water in the Nordic Seas
    (Nature Research, 2020-10-23) Huang, Jie ; Pickart, Robert S. ; Huang, Rui Xin ; Lin, Peigen ; Brakstad, Ailin ; Xu, Fanghua
    Overflow water from the Nordic Seas comprises the deepest limb of the Atlantic Meridional Overturning Circulation, yet questions remain as to where it is ventilated and how it reaches the Greenland-Scotland Ridge. Here we use historical hydrographic data from 2005-2015, together with satellite altimeter data, to elucidate the source regions of the Denmark Strait and Faroe Bank Channel overflows and the pathways feeding these respective sills. A recently-developed metric is used to calculate how similar two water parcels are, based on potential density and potential spicity. This reveals that the interior of the Greenland Sea gyre is the primary wintertime source of the densest portion of both overflows. After subducting, the water progresses southward along several ridge systems towards the Greenland-Scotland Ridge. Kinematic evidence supports the inferred pathways. Extending the calculation back to the 1980s reveals that the ventilation occurred previously along the periphery of the Greenland Sea gyre.
  • Article
    Structure and variability of the North Icelandic Jet from two years of mooring data
    (American Geophysical Union, 2019-06-04) Huang, Jie ; Pickart, Robert S. ; Valdimarsson, Héðinn ; Lin, Peigen ; Spall, Michael A. ; Xu, Fanghua
    Mooring data from September 2011 to July 2013 on the Iceland slope north of Denmark Strait are analyzed to better understand the structure and variability of the North Icelandic Jet (NIJ). Three basic configurations of the flow were identified: (1) a strong separated East Greenland Current (EGC) on the mid‐Iceland slope coincident with a weak NIJ on the upper slope, (2) a merged separated EGC and NIJ, and (3) a strong NIJ located at its climatological mean position, coincident with a weak signature of the separated EGC at the base of the Iceland slope. Our study reveals that the NIJ‐dominant scenario was present during different times of the year for the two successive mooring deployments—appearing mainly from September to February the first year and from January to July the second year. Furthermore, when this scenario was active it varied on short timescales. An energetics analysis demonstrates that the high‐frequency variability is driven by mean‐to‐eddy baroclinic conversion at the shoreward edge of the NIJ, consistent with previous modeling work. The seasonal timing of the NIJ dominant scenario is investigated in relation to the atmospheric forcing upstream of Denmark Strait. The resulting lagged correlations imply that strong turbulent heat fluxes in a localized region on the continental slope of Iceland, south of the Spar Fracture zone, lead to a stronger NIJ dominant state with a two‐month lag. This can be explained dynamically in terms of previous modeling work addressing the circulation response to dense water formation near an island.
  • Article
    Wintertime water mass transformation in the western Iceland and Greenland Seas
    (American Geophysical Union, 2021-07-14) Huang, Jie ; Pickart, Robert S. ; Bahr, Frank B. ; McRaven, Leah T. ; Xu, Fanghua
    Hydrographic and velocity data from a 2018 winter survey of the western Iceland and Greenland Seas are used to investigate the ventilation of overflow water feeding Denmark Strait. We focus on the two general classes of overflow water: warm, saline Atlantic-origin Overflow Water (AtOW) and cold, fresh Arctic-origin Overflow Water (ArOW). The former is found predominantly within the East Greenland Current (EGC), while the latter resides in the interior of the Iceland and Greenland Seas. Progressing north to south, the properties of AtOW in the EGC are modified diapycnally during the winter, in contrast to summer when along-isopycnal mixing dominates. The water column response to a 10-days cold-air outbreak was documented using repeat observations. During the event, the northerly winds pushed the freshwater cap of the EGC onshore, and convection modified the water at the seaward edge of the current. Lateral transfer of heat and salt from the core of AtOW in the EGC appears to have influenced some of this water mass transformation. The long-term evolution of the mixed layers in the interior was investigated using a 1-D mixing model. This suggests that, under strong atmospheric forcing, the densest component of ArOW can be ventilated in this region. Numerous anti-cyclonic eddies spawned from the EGC were observed during the winter survey, revealing that these features can play differing roles in modifying/prohibiting the open-ocean convection.
  • Article
    The Iceland Greenland Seas Project
    (American Meteorological Society, 2019-09-27) Renfrew, Ian A. ; Pickart, Robert S. ; Vage, Kjetil ; Moore, G. W. K. ; Bracegirde, Thomas J. ; Elvidge, Andrew D. ; Jeansson, Emil ; Lachlan-Cope, Thomas ; McRaven, Leah T. ; Papritz, Lukas ; Reuder, Joachim ; Sodemann, Harald ; Terpstra, Annick ; Waterman, Stephanie N. ; Valdimarsson, Héðinn ; Weiss, Albert ; Almansi, Mattia ; Bahr, Frank B. ; Brakstad, Ailin ; Barrell, Christopher ; Brooke, Jennifer K. ; Brooks, Barbara J. ; Brooks, Ian M. ; Brooks, Malcolm E. ; Bruvik, Erik Magnus ; Duscha, Christiane ; Fer, Ilker ; Golid, H. M. ; Hallerstig, M. ; Hessevik, Idar ; Huang, Jie ; Houghton, Leah A. ; Jonsson, Steingrimur ; Jonassen, Marius ; Jackson, K. ; Kvalsund, K. ; Kolstad, Erik W. ; Konstali, K. ; Kristiansen, Jorn ; Ladkin, Russell ; Lin, Peigen ; Macrander, Andreas ; Mitchell, Alexandra ; Olafsson, H. ; Pacini, Astrid ; Payne, Chris ; Palmason, Bolli ; Perez-Hernandez, M. Dolores ; Peterson, Algot K. ; Petersen, Guðrún N. ; Pisareva, Maria N. ; Pope, James O. ; Seidl, Andrew D. ; Semper, Stefanie ; Sergeev, Denis ; Skjelsvik, Silje ; Søiland, Henrik ; Smith, D. ; Spall, Michael A. ; Spengler, Thomas ; Touzeau, Alexandra ; Tupper, George H. ; Weng, Y. ; Williams, Keith D. ; Yang, Xiaohau ; Zhou, Shenjie
    The Iceland Greenland Seas Project (IGP) is a coordinated atmosphere–ocean research program investigating climate processes in the source region of the densest waters of the Atlantic meridional overturning circulation. During February and March 2018, a field campaign was executed over the Iceland and southern Greenland Seas that utilized a range of observing platforms to investigate critical processes in the region, including a research vessel, a research aircraft, moorings, sea gliders, floats, and a meteorological buoy. A remarkable feature of the field campaign was the highly coordinated deployment of the observing platforms, whereby the research vessel and aircraft tracks were planned in concert to allow simultaneous sampling of the atmosphere, the ocean, and their interactions. This joint planning was supported by tailor-made convection-permitting weather forecasts and novel diagnostics from an ensemble prediction system. The scientific aims of the IGP are to characterize the atmospheric forcing and the ocean response of coupled processes; in particular, cold-air outbreaks in the vicinity of the marginal ice zone and their triggering of oceanic heat loss, and the role of freshwater in the generation of dense water masses. The campaign observed the life cycle of a long-lasting cold-air outbreak over the Iceland Sea and the development of a cold-air outbreak over the Greenland Sea. Repeated profiling revealed the immediate impact on the ocean, while a comprehensive hydrographic survey provided a rare picture of these subpolar seas in winter. A joint atmosphere–ocean approach is also being used in the analysis phase, with coupled observational analysis and coordinated numerical modeling activities underway.
  • Article
    Role of air-sea heat flux on the transformation of Atlantic Water encircling the Nordic Seas
    (Nature Research, 2023-01-10) Huang, Jie ; Pickart, Robert S. ; Chen, Zhuomin ; Huang, Rui Xin
    The warm-to-cold densification of Atlantic Water (AW) around the perimeter of the Nordic Seas is a critical component of the Atlantic Meridional Overturning Circulation (AMOC). However, it remains unclear how ongoing changes in air-sea heat flux impact this transformation. Here we use observational data, and a one-dimensional mixing model following the flow, to investigate the role of air-sea heat flux on the cooling of AW. We focus on the Norwegian Atlantic Slope Current (NwASC) and Front Current (NwAFC), where the primary transformation of AW occurs. We find that air-sea heat flux accounts almost entirely for the net cooling of AW along the NwAFC, while oceanic lateral heat transfer appears to dominate the temperature change along the NwASC. Such differing impacts of air-sea interaction, which explain the contrasting long-term changes in the net cooling along two AW branches since the 1990s, need to be considered when understanding the AMOC variability.
  • Article
    Coupled atmosphere–ocean observations of a cold‐air outbreak and its impact on the Iceland Sea
    (Royal Meteorological Society, 2022-12-24) Renfrew, Ian A. ; Huang, Jie ; Semper, Stefanie ; Barrell, Christopher ; Terpstra, Annick ; Pickart, Robert S. ; Våge, Kjetil ; Elvidge, Andrew D. ; Spengler, Thomas ; Strehl, Anna‐Marie ; Weiss, Alexandra
    Marine cold‐air outbreaks (CAOs) are vigorous equatorward excursions of cold air over the ocean, responsible for the majority of wintertime oceanic heat loss from the subpolar seas of the North Atlantic. However, the impact of individual CAO events on the ocean is poorly understood. Here we present the first coupled observations of the atmosphere and ocean during a wintertime CAO event, between 28 February and 13 March 2018, in the subpolar North Atlantic region. Comprehensive observations are presented from five aircraft flights, a research vessel, a meteorological buoy, a subsurface mooring, an ocean glider, and an Argo float. The CAO event starts abruptly with substantial changes in temperature, humidity and wind throughout the atmospheric boundary layer. The CAO is well mixed vertically and, away from the sea‐ice edge, relatively homogeneous spatially. During the CAO peak, higher sensible heat fluxes occupy at least the lowest 200 m of the atmospheric boundary layer, while higher latent heat fluxes are confined to the surface layer. The response of the ocean to the CAO is spatially dependent. In the interior of the Iceland Sea the mixed layer cools, while in the boundary current region it warms. In both locations, the mixed layer deepens and becomes more saline. Combining our observations with one‐dimensional mixed‐layer modelling, we show that in the interior of the Iceland Sea, atmospheric forcing dominates the ocean response. In contrast, in the boundary current region lateral advection and mixing counteract the short‐term impact of the atmospheric forcing. Time series observations of the late‐winter period illustrate a highly variable ocean mixed layer, with lateral advection and mixing often masking the ocean's general cooling and deepening response to individual CAO events.Simultaneous observations of the atmosphere and ocean during a cold‐air outbreak over the Iceland Sea. The top panel shows near‐surface potential temperature from two research flights and a research vessel at the onset of the event; the distribution is relatively homogeneous, although affected by the sea‐ice off the East Greenland coast. The bottom panel shows observed ocean mixed‐layer depth during the first part of the event; the response of the ocean is spatially dependent due to counteracting vertical and lateral processes.