Seasonality and timing of sea ice mass balance and heat fluxes in the Arctic transpolar drift during 2019–2020

Lei, Ruibo; Cheng, Bin; Hoppmann, Mario; Zhang, Fanyi; Zuo, Guangyu; Hutchings, Jennifer K.; Lin, Long; Lan, Musheng; Wang, Hangzhou; Regnery, Julia; Krumpen, Thomas; Haapala, Jari; Rabe, Benjamin; Perovich, Donald K.; Nicolaus, Marcel

doi:10.1525/elementa.2021.000089

Cited by 42 publications

(48 citation statements)

References 52 publications

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“…Third, the majority of IMBs were deployed on multiyear undeformed ice (Planck et al, 2020), so the basal melt and freeze onsets of seasonal ice are underrepresented. Compared to multiyear ice, seasonal ice has higher bulk brine, resulting in a smaller specific heat capacity and latent heat of fusion (Tucker et al, 1987;Wang et al, 2020), as well as a higher permeability during the summer (Lei et al, 2022), thus affecting the sea ice basal melt and freeze processes. Finally, due to the limited vertical observation range of ocean profile automatic observation instruments, some special processes near the ice bottom, such as supercooling and false bottoms, were not characterized well.…”

Section: Discussionmentioning

confidence: 99%

Changes in the annual sea ice freeze–thaw cycle in the Arctic Ocean from 2001 to 2018

et al. 2022

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Abstract. The annual sea ice freeze–thaw cycle plays a crucial role in the Arctic atmosphere—ice–ocean system, regulating the seasonal energy balance of sea ice and the underlying upper-ocean. Previous studies of the sea ice freeze–thaw cycle were often based on limited accessible in situ or easily available remotely sensed observations of the surface. To better understand the responses of the sea ice to climate change and its coupling to the upper ocean, we combine measurements of the ice surface and bottom using multisource data to investigate the temporal and spatial variations in the freeze–thaw cycle of Arctic sea ice. Observations by 69 sea ice mass balance buoys (IMBs) collected from 2001 to 2018 revealed that the average ice basal melt onset in the Beaufort Gyre occurred on 23 May (±6 d), approximately 17 d earlier than the surface melt onset. The average ice basal melt onset in the central Arctic Ocean occurred on 17 June (±9 d), which was comparable with the surface melt onset. This difference was mainly attributed to the distinct seasonal variations of oceanic heat available to sea ice melt between the two regions. The overall average onset of basal ice growth of the pan Arctic Ocean occurred on 14 November (±21 d), lagging approximately 3 months behind the surface freeze onset. This temporal delay was caused by a combination of cooling the sea ice, the ocean mixed layer, and the ocean subsurface layer, as well as the thermal buffering of snow atop the ice. In the Beaufort Gyre region, both (Lagrangian) IMB observations (2001–2018) and (Eulerian) moored upward-looking sonar (ULS) observations (2003–2018) revealed a trend towards earlier basal melt onset, mainly linked to the earlier warming of the surface ocean. A trend towards earlier onset of basal ice growth was also identified from the IMB observations (multiyear ice), which we attributed to the overall reduction of ice thickness. In contrast, a trend towards delayed onset of basal ice growth was identified from the ULS observations, which was explained by the fact that the ice cover melted almost entirely by the end of summer in recent years.

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Section: Discussionmentioning

confidence: 99%

Changes in the annual sea ice freeze–thaw cycle in the Arctic Ocean from 2001 to 2018

et al. 2022

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“…Nevertheless, challenges facing intricately detailed measurements of the LFI mass balance, including internal gap layers that can only be detected manually (Zhao et al, 2022), still remain. To capture the coupling process between the sea ice mass balance and ice-associated ecosystems, better integrated buoys are required to make synchronous measurements 580 of the sea ice mass balance, biogeochemical, and optical parameters, for example, the multi-sensor Unmanned Ice Station (Lei et al, 2022). Further developments of the LFI monitoring instrumentation and observation network (AFIN) are urgently needed to better understand the various physical-biochemical processes and the importance of LFI to the Antarctic system, especially in coastal regions.…”

Section: Discussionmentioning

confidence: 99%

“…9c), suggesting the possibility of flooding. Ice surface flooding is controlled by upward brine percolation when the ice layer is warmer than a critical temperature (Golden et al, 1998) or through macroscopic fractures when the ice surface is depressed because of local ice deformation (Lei et al, 2022). Seasonally, ice bulk temperatures usually reach the critical temperature of 500 −5 °C around early November.…”

Section: Flooding and Snow Ice Formationmentioning

confidence: 99%

Seasonal and interannual variations in the landfast ice mass balance between 2009 and 2018 in Prydz Bay, East Antarctica

Lei

Heil

et al. 2022

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Abstract. Landfast ice (LFI) plays an important role in the climate and ecosystem of the Antarctic coastal regions. We investigate the LFI snow and ice mass balance in Prydz Bay using data collected by 11 sea ice mass balance buoys (IMBs). The observations were distributed offshore from the Chinese Zhongshan Station (ZS) and Australian Davis Station (DS), and covered 2009–2010, 2013–2016 and 2018 ice seasons. The observed LFI annual maximum ice thickness and snow depth were 1.59±0.17 and 0.11–0.76 m off ZS and 1.64±0.08 and 0.11–0.38 m off DS, respectively. Early in the ice growth season, the LFI basal growth rate near DS (0.6±0.2 cm d−1) exceeds that around ZS (0.5±0.2 cm d−1). This is attributed to cooler air temperature and lower oceanic heat flux at that time in the DS region. Snow ice contributes up to 27 % of the LFI total ice thickness at the offshore site close to ground icebergs off ZS because of the substantial snow accumulation. Larger interannual and local spatial variabilities for the seasonality of LFI mass balance identified at ZS than at DS are due to local differences in topography and katabatic wind regime. Air temperature anomalies are more important in regulating the LFI growth rate in the early ice growth season because of thinner sea ice relative to later seasons due to the weak thermal inertia of thin ice. Offshore from ZS, the year-round supercooled water from the nearby Dålk Glacier reduces the oceanic heat flux, promoting the LFI growth at the associated sites throughout the entire ice growth season. During late austral spring and summer, we found the increased oceanic heat flux leading to a reduction of LFI growth at all investigated sites. At interannual timescale, we found that variability of LFI properties across the study domain prevailed, over any trend during the recent decades. We argue that an increased understanding of local atmospheric and oceanic conditions, as well as surface morphology and coastal bathymetry, are required to improve the Antarctic LFI modelling at local and regional scale.

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“…Therefore, compared to the atmospheric and oceanic forcing entering the freezing season in mid-September (Rinke et al, 2021;Kawaguchi et al, 2022), the ice bottom began to grow ~2 months later for the level ice (1.42 m), which could be mainly attributed to the release of specific heat from the thermal storage of ice layer itself (e.g., Lin et al, 2022). From mid-September to mid-December 2020, the accumulation of snow from 0.14 to 0.42 m was significantly greater than that observed on the level ice over the MOSAiC CO1 floe, where snow depth increased to ~0.15 m only by mid-December 2019 (Lei et al, 2022;Wagner et al, 2022). This discrepancy can be related to the relatively large cumulative precipitation equivalent (138 mm) from 15 September to 31 December 2020, which was ~75% larger than the 1979-2020 Climatology (Figure 4e).…”

Section: Onset Of Sea Ice Freezingmentioning

confidence: 93%

Sea ice in the Arctic Transpolar Drift in 2020/21: thermodynamic evolution of different ice types

Lei

Hoppmann

Cheng

et al. 2023

Preprint

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Abstract. Sea ice properties are extremely inhomogeneous, in particular on the floe-scale. Different characteristic local features, such as melt ponds and pressure ridges, profoundly impact the thermodynamic evolution of the ice pack even in a kilometre-scale domain, and the associated processes are still not well represented in current climate models. To better characterize the freezing and melting of different types of sea ice, we deployed four sea ice mass balance buoys on an ice floe close to the North Pole during the second drift of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) in August 2020. The study sites included level first-year ice, an open melt pond, and an unconsolidated ridge. The floe slowly drifted southwards from October 2020 to early March 2021 but shifted to a more rapid drift from March to July 2021. This drifting pattern, together with a large snow accumulation, relatively warm air temperatures, and a rapid increase in oceanic heat close to Fram Strait, determined the seasonal evolution of the ice mass balance. Storms, accompanied by higher air temperatures and enhanced ice dynamics, were the main cause of the formation of snow ice or superimposed ice. Although the 0.24-m deep melt pond was completely refrozen by 5 September, the relatively large snow accumulation and the heat storage with the rotten ice layer delayed ice basal growth beyond the last observation at this site in mid-February 2021. At the ridge site, the macroporosity of the unconsolidated layer was estimated between 0.005 and 0.755. The freezing of internal voids also delayed the ridge basal growth, which was not observed until 26 April 2021. Thus, the refreezing of ponded ice and voids within the unconsolidated ridges amplifies the anisotropy of the heat exchange between the ice and the lower atmosphere/upper ocean. Our results provide an important physical background for further interdisciplinary studies related to the MOSAiC observations and can be used to optimize the parameterization of freezing processes related to melt ponds and ice ridges in sea ice numerical models.

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Seasonality and timing of sea ice mass balance and heat fluxes in the Arctic transpolar drift during 2019–2020

Cited by 42 publications

References 52 publications

Changes in the annual sea ice freeze–thaw cycle in the Arctic Ocean from 2001 to 2018

Changes in the annual sea ice freeze–thaw cycle in the Arctic Ocean from 2001 to 2018

Seasonal and interannual variations in the landfast ice mass balance between 2009 and 2018 in Prydz Bay, East Antarctica

Sea ice in the Arctic Transpolar Drift in 2020/21: thermodynamic evolution of different ice types

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