Method for diagnosing abnormal sea temperature of subsurface layer of Eurasian basin of Arctic Ocean caused by passing of Arctic cyclones

Abstract

The invention discloses a method for diagnosing the abnormal sea temperature of the subsurface layer of the Eurasian basin of the Arctic Ocean caused by Arctic cyclones, and belongs to the technical field of sea temperature abnormity diagnosis. The method provides a set of systematic diagnosis steps: (1) acquiring air pressure data, and tracking a north cyclone path and intensity through a cyclone detection algorithm; (2) acquiring data of wind speed, sea ice concentration, seawater temperature and salinity during the passing period of the arctic cyclones; (3) considering the effect of sea ice, and calculating the influence depth of the north cyclone on the European Asia north ice ocean; (4) calculating the depth of the cold-salt spring layer of the European Arctic Ocean; (5) comparing the difference between the cyclone influence depth and the cold salt spring layer depth; and (6) when the arctic cyclone influence depth is greater than the cold salt spring layer depth, judging that the phenomenon of abnormal temperature rise of the subsurface seawater occurs. According to the method, the influence of unique ocean stratification and sea ice of the Eurasian basin of the Arctic Ocean is fully considered, a diagnosis method is provided for scientifically evaluating the response of the Eurasian basin of the Arctic Ocean to the Arctic cyclones, and the method has remarkable scientific value and practical application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of sea temperature anomaly diagnosis, and in particular to a method for diagnosing subsurface sea temperature anomaly in the Eurasian Basin of the Arctic Ocean caused by the passage of an Arctic cyclone. Background Art

[0002] In recent years, the Arctic has been warming significantly faster than the global average. One of the key drivers of the rapid melting of Arctic sea ice is the massive influx of warm water from the Atlantic Ocean, a phenomenon known as "Atlanticization". In the Eurasian Basin of the Arctic Ocean, "Atlanticization" is manifested as weakening of upper ocean stratification and increased heat release from warm water in the middle layer, which further accelerates the melting of sea ice. The Eurasian Arctic Ocean has a unique marine stratification, consisting of surface sea ice, a cold fresh water layer, and warmer and saltier Atlantic water at the bottom. This stratification relies on density differences to exist stably. Fresh water with lower salinity covers warm water due to its strong buoyancy and forms a steep cold halocline layer (CHL), which effectively isolates the direct thermal threat of warm Atlantic water to sea ice.

[0003] This stable stratified structure of the Eurasian Arctic Ocean may be broken when a strong Arctic cyclone passes through. The strong winds and dynamic disturbances brought by the Arctic cyclone can weaken the stability of the CHL and even cause the warm water in the Atlantic Ocean to break through the thermocline and upwell, resulting in an abnormal increase in subsurface sea temperature. This phenomenon will not only significantly accelerate the melting of sea ice, but may also change the local ocean heat distribution and material circulation. However, there is currently a lack of a method to diagnose the impact of the passage of the Arctic cyclone on the subsurface sea temperature anomaly in the Eurasian Basin of the Arctic Ocean. Summary of the invention

[0004] The purpose of the present invention is to provide a new method for diagnosing subsurface sea temperature anomalies in the Eurasian Basin of the Arctic Ocean during Arctic cyclones, which can solve the problem of lack of systematic coupling between the impact depth of Arctic cyclones and the characteristics of ocean stratification, and has theoretical and practical significance.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme to diagnose the sea temperature anomaly in the subsurface layer of the Eurasian Arctic Ocean caused by the Arctic cyclone, including the following steps: (1) Obtain air pressure data and use cyclone detection algorithms to identify the intensity and movement path of Arctic cyclones; (2) Collect data on wind speed, sea ice density, sea temperature, and salinity during the passage of Arctic cyclones, and perform quality control and spatial interpolation; (3) Combined with the Ekman depth theory, the impact depth of the Arctic cyclone on the ocean water body during the passage of the sea ice is calculated as follows: (1) Where DE represents the influence depth of the Arctic cyclone, SIC is the sea ice density, θ is the geographic latitude, and Vmax represents the maximum sea surface wind speed; (4) Based on the temperature and salinity data, the depth of the cold halocline in the Eurasian Basin of the Arctic Ocean is defined as the position where the ratio of the density gradient caused by temperature to the density gradient caused by salinity is equal to 0.05, as follows: (2) In the formula, R represents the gradient ratio of temperature to salinity, α is the thermal expansion coefficient, θ is the seawater temperature, β is the salinity contraction coefficient, S is the salt water depth, and z is the seawater depth; (5) Compare the influence depth of the Arctic cyclone with the depth of the cold halocline to diagnose the subsurface sea temperature anomaly events caused by the Arctic cyclone.

[0006] The technical problem to be solved by the present invention can also be further achieved by the following technical scheme. In the above-mentioned method for diagnosing the abnormal subsurface sea temperature in the Eurasian Basin of the Arctic Ocean caused by the passage of the Arctic cyclone, in the step five, when the cyclone influence depth is greater than the cold halocline depth, it is determined that warm water below the cold halocline is upwelling and abnormal warming occurs in the subsurface.

[0007] Furthermore, the air pressure and wind speed data can be obtained from the ERA5 reanalysis product of the European Centre for Medium-Range Weather Forecasts (https: / / www.ecmwf.int / en / forecasts / dataset / ecmwf-reanalysis-v5), and the sea ice density, sea water temperature and salinity data can be obtained from the Copernicus Marine Environment Monitoring Service (https: / / marine.copernicus.eu / ).

[0008] The above technical solution can achieve the following beneficial effects: This method is a new method for diagnosing subsurface sea temperature anomalies in the Eurasian Basin of the Arctic Ocean. The invention specifically considers the influence of sea ice cover and the unique ocean stratification of the Eurasian Arctic Ocean, which enables a more accurate assessment of the abnormal response of subsurface sea temperature during the influence of Arctic cyclones, providing an important reference for related climate change and marine environment predictions. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Flowchart for diagnosing subsurface SST anomalies in the Eurasian Basin of the Arctic Ocean during Arctic cyclones; Figure 2 This is a graph showing the changes in Ekman suction speed, sea ice density, and subsurface temperature before and after the passage of the Arctic cyclone from November 15 to 17, 2020. The black line is the movement path of the Arctic cyclone, and the yellow box is the main affected area when the Arctic cyclone is the strongest; Figure 3 This is the distribution map of the cold halocline in the Eurasian Basin of the Arctic Ocean in November 2020; Figure 4 This is a graph showing the changes in the maximum ocean impact depth and average subsurface sea temperature in the main affected areas before and after the passage of the Arctic cyclone. DETAILED DESCRIPTION

[0010] The specific technical solutions of the present invention are further described below with reference to the accompanying drawings, so that those skilled in the art can further understand the present invention without limiting the rights thereof.

[0011] In order to fully disclose the present invention, the embodiment takes the Arctic cyclone detected as active in the Eurasian Basin of the Arctic Ocean from November 15 to 17, 2020 as an example. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0012] Example 1, reference Figure 1-Figure 4 , a method for diagnosing subsurface sea temperature anomalies in the Eurasian Basin of the Arctic Ocean caused by the passage of an Arctic cyclone, comprising the following steps, (1) Obtaining air pressure data and identifying cyclone paths: Using the air pressure data provided by the ERA5 reanalysis product of the European Centre for Medium-Range Weather Forecasts, the Lagrangian method is used to track the center position of the Arctic cyclone, and the intensity, position and movement path of the cyclone are identified; in this case, the Arctic cyclone was mainly active in the Eurasian Basin of the Arctic Ocean from November 15 to 17, 2020, and developed to its strongest on November 16, after which its intensity gradually weakened; considering the longitude and latitude deformations in high-latitude regions, the box (82°N -84°N, 39.5°E-47.5°E) is taken as the key research area.

[0013] (2) Collect data on wind speed, sea ice concentration, sea temperature and salinity during cyclones: The sea ice concentration, sea water temperature and salinity data provided by the Copernicus Marine Environment Monitoring Service were used to obtain ocean parameters with multiple spatial resolutions during the Arctic cyclone (November 15-17, 2020), with the subsurface layer defined as a depth of 100 meters. These data were quality controlled and spatially interpolated to ensure the accuracy and completeness of the data, and the ocean state in the cyclone-affected area was extracted; see Figure 2 , before and after the passage of the Arctic cyclone from November 15 to 17, 2020, the Ekman suction velocity, sea ice density, and subsurface temperature changed significantly. When the Arctic cyclone had the strongest impact on November 16, the Ekman suction velocity in the box reached a maximum of 1.98×10 5 ms -1The average sea ice density decreased significantly from 0.72 on November 15 to 0.69 on November 16, and the subsurface temperature also increased from 1.49℃ before the transit to 1.54℃ after the transit, indicating that the Arctic cyclone may have disturbed the ocean stratification and was affected by the heat from the warm Atlantic water at the bottom.

[0014] (3) Calculate the depth of the impact of the Arctic cyclone on the ocean: Combined with the Ekman depth theory, the disturbance depth of the ocean water body caused by the Arctic cyclone during its passage is calculated. The specific formula is: (1) Where DE represents the influence depth of the Arctic cyclone, SIC is the sea ice density, θ is the geographic latitude, V max Represents the maximum sea surface wind speed; in this embodiment, by combining meteorological data and sea ice density, it is calculated that the depth of upper sea water disturbance caused by Arctic cyclones in a specific area can reach 72 m.

[0015] (4) Calculate the depth of the cold salt layer: Using the temperature and salinity data of November 2020, the average depth of the cold halocline in the Eurasian Basin of the Arctic Ocean in November was defined by the ratio of the density gradient caused by temperature to the density gradient caused by salinity equal to 0.05. The specific formula is: (2) Where R represents the gradient ratio of temperature to salinity, α is the thermal expansion coefficient, θ is the seawater temperature, β is the salinity contraction coefficient, S is the saltwater depth, and z is the seawater depth. Figure 3 , through the calculation of the depth of the cold halocline, the average depth of the cold halocline in the key study area in November 2020 was 58.3 m.

[0016] (5) Compare the influence depth of the Arctic cyclone with the depth of the cold halocline to diagnose the subsurface sea temperature anomaly: By comparing the cyclone influence depth calculated in step 3 and the cold halocline depth calculated in step 4, diagnose whether abnormal subsurface seawater warming or cooling occurs; refer to Figure 4 When the Arctic cyclone passed on November 16, 2020, the impact depth was greater than the average depth of the cold halocline. Warm water rose from the deep layer and broke through the cold halocline, causing the subsurface sea water temperature to rise abnormally.

[0017] The present invention provides a new method for diagnosing subsurface sea temperature anomalies caused by the passage of Arctic cyclones in the Eurasian Basin of the Arctic Ocean, which can effectively evaluate the impact of Arctic cyclones on changes in the subsurface heat distribution of the ocean. This method not only improves the accuracy of diagnosing the impact of Arctic cyclones, but also reveals the mechanism of the unique ocean stratification changes in the Eurasian Basin of the Arctic Ocean on the ocean thermodynamic response.

[0018] The above are all preferred embodiments of the present invention. For ordinary technicians in this technical field, without departing from the principle of the present invention, various equivalent modifications to the present invention belong to the protection scope of the claims attached to this application.

Claims

1. A method for diagnosing subsurface sea temperature anomalies in the Eurasian Basin of the Arctic Ocean caused by the passage of an Arctic cyclone, characterized in that: The following steps are included: (1) Obtain air pressure data and use cyclone detection algorithms to identify the movement path and intensity of Arctic cyclones; (2) Collect data on wind speed, sea ice density, sea temperature, and salinity during the passage of Arctic cyclones, and perform quality control and spatial interpolation; (3) Combined with the Ekman depth theory, the impact depth of the Arctic cyclone on the ocean water body during the passage of the sea ice is calculated: (1) Where DE represents the influence depth of the Arctic cyclone, SIC is the sea ice density, θ is the geographic latitude, and V max represents the maximum sea surface wind speed; (4) Determine the depth of the cold halocline based on the temperature and salt profile data of the Eurasian Basin in the Arctic Ocean: (2) In the formula, R represents the gradient ratio of temperature to salinity, α is the thermal expansion coefficient, θ is the seawater temperature, β is the salinity contraction coefficient, S is the salt water depth, and z is the seawater depth; (5) Compare the impact depth of the Arctic cyclone with the depth of the cold halocline to determine the impact of the Arctic cyclone on the subsurface sea temperature. When the disturbance depth of the Arctic cyclone is greater than the depth of the cold halocline, it causes the warm water below the cold halocline to upwell, resulting in abnormal warming events in the subsurface.

2. A method for diagnosing subsurface sea temperature anomalies in the Eurasian Basin of the Arctic Ocean caused by the passage of an Arctic cyclone according to claim 1, characterized in that: The unique ocean stratification in the Eurasian Basin of the Arctic Ocean has a higher heat content at its bottom, which is influenced by the warm waters of the Atlantic Ocean.

3. The method for diagnosing subsurface sea temperature anomalies in the Eurasian Basin of the Arctic Ocean caused by the passage of an Arctic cyclone according to claim 1, characterized in that: In step (3), the impact depth of the Arctic cyclone is considered when the Arctic sea ice is covered.

4. The method for diagnosing subsurface sea temperature anomalies in the Eurasian Basin of the Arctic Ocean caused by the passage of an Arctic cyclone according to claim 1, characterized in that: In step (4), the depth of the cold halocline is calculated using a gradient ratio of temperature to salinity equal to 0.

05.

5. The method for diagnosing subsurface sea temperature anomalies in the Eurasian Basin of the Arctic Ocean caused by the passage of an Arctic cyclone according to claim 1, characterized in that: The basis for determining the abnormal warming phenomenon in step (5) is that when the influence depth of the Arctic cyclone is greater than the depth of the cold halocline, abnormal warming occurs in the subsurface layer.

Images